]> git.sesse.net Git - remoteglot/blobdiff - www/js/remoteglot.js
Handle streaming PGNs, like from Lichess (although this might break non-streaming...
[remoteglot] / www / js / remoteglot.js
index e7c97e54736b4fda6049e677757983dd2cdf4e9a..d36bf9e5117bed15911ea36263ed5084fc6f0c48 100644 (file)
@@ -1,13 +1,14 @@
 (function() {
+'use strict';
 
 /**
  * Version of this script. If the server returns a version larger than
  * this, it is a sign we should reload to upgrade ourselves.
  *
- * @type {Number}
+ * @type {number}
  * @const
  * @private */
-var SCRIPT_VERSION = 2021021200;
+let SCRIPT_VERSION = 2023122700;
 
 /**
  * The current backend URL.
@@ -15,14 +16,14 @@ var SCRIPT_VERSION = 2021021200;
  * @type {!string}
  * @private
  */
-var backend_url = "/analysis.pl";
-var backend_hash_url = "/hash";
+let backend_url = "/analysis.pl";
+let backend_hash_url = "/hash";
 
 /** @type {window.ChessBoard} @private */
-var board = null;
+let board = null;
 
 /** @type {boolean} @private */
-var board_is_animating = false;
+let board_is_animating = false;
 
 /**
  * The most recent analysis data we have from the server
@@ -30,7 +31,7 @@ var board_is_animating = false;
  *
  * @type {?Object}
  * @private */
-var current_analysis_data = null;
+let current_analysis_data = null;
 
 /**
  * If we are displaying previous analysis or from hash, this is non-null,
@@ -39,7 +40,7 @@ var current_analysis_data = null;
  * @type {?Object}
  * @private
  */
-var displayed_analysis_data = null;
+let displayed_analysis_data = null;
 
 /**
  * Games currently in progress, if any.
@@ -54,7 +55,7 @@ var displayed_analysis_data = null;
  * }>}
  * @private
  */
-var current_games = null;
+let current_games = null;
 
 /** @type {Array.<{
  *      from_col: number,
@@ -67,65 +68,78 @@ var current_games = null;
  * }>}
  * @private
  */
-var arrows = [];
+let arrows = [];
 
 /** @type {Array.<Array.<boolean>>} */
-var occupied_by_arrows = [];
+let occupied_by_arrows = [];
 
 /** Currently displayed refutation lines (on-screen).
  * Can either come from the current_analysis_data, displayed_analysis_data,
- * or hash_refutation_lines.
+ * or hash_refutation_lines (choose_displayed_refutation_lines() chooses which one).
+ *
+ * @typedef {{
+ *     score: Array,
+ *     depth: string,
+ *     pv: Array.<string>,
+ *     move: string
+ * }}
+ * @private
  */
-var refutation_lines = [];
+var RefutationLine;
 
 /** Refutation lines from current hash probe.
- *
  * If non-null, will override refutation lines from the base position.
- * Note that these are relative to display_fen, not base_fen.
+ *
+ * @type {Array.<RefutationLine>}
  */
-var hash_refutation_lines = null;
-
-/** @type {!number} @private */
-var move_num = 1;
+let hash_refutation_lines = null;
 
-/** @type {!string} @private */
-var toplay = 'W';
+/**
+ * What FEN hash_refutation_lines is relative to.
+ */
+let hash_refutation_lines_base_fen = null;
 
 /** @type {number} @private */
-var ims = 0;
+let ims = 0;
 
 /** @type {boolean} @private */
-var truncate_display_history = true;
+let truncate_display_history = true;
 
 /** @type {!string|undefined} @private */
-var highlight_from = undefined;
+let highlight_from = undefined;
 
 /** @type {!string|undefined} @private */
-var highlight_to = undefined;
+let highlight_to = undefined;
 
 /** The HTML object of the move currently being highlighted (in red).
- * @type {?jQuery}
+ * @type {?Element}
  * @private */
-var highlighted_move = null;
+let highlighted_move = null;
 
 /** Currently suggested/recommended move when dragging.
  * @type {?{from: !string, to: !string}}
  * @private
  */
-var recommended_move = null;
+let recommended_move = null;
 
 /** If reverse-dragging (dragging from the destination square to the
  * source square), the destination square.
  * @type {?string}
  * @private
  */
-var reverse_dragging_from = null;
+let reverse_dragging_from = null;
 
 /** @type {?number} @private */
-var unique = null;
+let unique = null;
+
+/** @type {?string} @private */
+let admin_password = null;
 
 /** @type {boolean} @private */
-var enable_sound = false;
+let enable_sound = false;
+
+/** @type {!number} @private */
+let delay_ms = 0;
 
 /**
  * Our best estimate of how many milliseconds we need to add to 
@@ -135,36 +149,40 @@ var enable_sound = false;
  * @type {?number}
  * @private
  */
-var client_clock_offset_ms = null;
+let client_clock_offset_ms = null;
 
-var clock_timer = null;
+let clock_timer = null;
 
 /** The current position being analyzed, represented as a FEN string.
  * Note that this is not necessarily the same as display_fen.
  * @type {?string}
  * @private
  */
-var base_fen = null;
+let base_fen = null;
 
 /** The current position on the board, represented as a FEN string.
  * Note that board.fen() does not contain e.g. who is to play.
  * @type {?string}
  * @private
  */
-var display_fen = null;
+let display_fen = null;
 
 /** @typedef {{
  *    start_fen: string,
  *    pv: Array.<string>,
- *    move_num: number,
- *    toplay: string,
  *    scores: Array<{first_move: number, score: Object}>,
  *    start_display_move_num: number
- * }} DisplayLine
+ * }}
+ *
+ * "start_display_move_num" is the (half-)move number to start displaying the PV at,
+ * i.e., the index into pv.
  *
- * "start_display_move_num" is the (half-)move number to start displaying the PV at.
- * "score" is also evaluated at this point.
+ * "score" is also evaluated at this point. scores can be empty and is frequently
+ * sparse; it's generally only really useful for history (we obviously don't know
+ * much about how the score will * move during e.g. a PV, except that a mate/TB
+ * counter might go down).
  */
+var DisplayLine;
 
 /** All PVs that we currently know of.
  *
@@ -175,61 +193,65 @@ var display_fen = null;
  * @type {Array.<DisplayLine>}
  * @private
  */
-var display_lines = [];
+let display_lines = [];
 
 /** @type {?DisplayLine} @private */
-var current_display_line = null;
+let current_display_line = null;
 
 /** @type {boolean} @private */
-var current_display_line_is_history = false;
+let current_display_line_is_history = false;
 
-/** @type {?number} @private */
-var current_display_move = null;
+/** @type {?number} @private
+ *
+ * The highlighted/used/shown move in current_display_line.pv, in terms of absolute index
+ * (not relative to e.g. the start FEN).
+ */
+let current_display_move = null;
 
 /**
  * The current backend request to get main analysis (not history), if any,
  * so that we can abort it.
  *
- * @type {?jqXHR}
+ * @type {?AbortController}
  * @private
  */
-var current_analysis_xhr = null;
+let current_analysis_xhr = null;
 
 /**
  * The current timer to fire off a request to get main analysis (not history),
  * if any, so that we can abort it.
  *
- * @type {?Number}
+ * @type {?number}
  * @private
  */
-var current_analysis_request_timer = null;
+let current_analysis_request_timer = null;
 
 /**
  * The current backend request to get historic data, if any.
  *
- * @type {?jqXHR}
+ * @type {?AbortController}
  * @private
  */
-var current_historic_xhr = null;
+let current_historic_xhr = null;
 
 /**
  * The current backend request to get hash probes, if any, so that we can abort it.
  *
- * @type {?jqXHR}
+ * @type {?AbortController}
  * @private
  */
-var current_hash_xhr = null;
+let current_hash_xhr = null;
 
 /**
  * The current timer to display hash probe information (it could be waiting on the
  * board to stop animating), if any, so that we can abort it.
  *
- * @type {?Number}
+ * @type {?number}
  * @private
  */
-var current_hash_display_timer = null;
+let current_hash_display_timer = null;
 
-var supports_html5_storage = function() {
+function supports_html5_storage() {
        try {
                return 'localStorage' in window && window['localStorage'] !== null;
        } catch (e) {
@@ -239,92 +261,117 @@ var supports_html5_storage = function() {
 
 // Make the unique token persistent so people refreshing the page won't count twice.
 // Of course, you can never fully protect against people deliberately wanting to spam.
-var get_unique = function() {
-       var use_local_storage = supports_html5_storage();
-       if (use_local_storage && localStorage['unique']) {
-               return localStorage['unique'];
+function get_unique() {
+       let use_local_storage = supports_html5_storage();
+       if (use_local_storage && window['localStorage']['unique']) {
+               return window['localStorage']['unique'];
        }
-       var unique = Math.random();
+       let unique = Math.random();
        if (use_local_storage) {
-               localStorage['unique'] = unique;
+               window['localStorage']['unique'] = unique;
        }
        return unique;
 }
 
-var request_update = function() {
+function request_update() {
        current_analysis_request_timer = null;
 
-       current_analysis_xhr = $.ajax({
-               url: backend_url + "?ims=" + ims + "&unique=" + unique
-       }).done(function(data, textstatus, xhr) {
-               sync_server_clock(xhr.getResponseHeader('Date'));
-               ims = xhr.getResponseHeader('X-RGLM');
-               var num_viewers = xhr.getResponseHeader('X-RGNV');
-               var new_data;
-               if (Array.isArray(data)) {
-                       new_data = JSON.parse(JSON.stringify(current_analysis_data));
-                       JSON_delta.patch(new_data, data);
-               } else {
-                       new_data = data;
-               }
+       let handle_err = () => {
+               // Backend error or similar. Wait ten seconds, then try again.
+               current_analysis_request_timer = setTimeout(function() { request_update(); }, 10000);
+       };
 
-               var minimum_version = xhr.getResponseHeader('X-RGMV');
-               if (minimum_version && minimum_version > SCRIPT_VERSION) {
-                       // Upgrade to latest version with a force-reload.
-                       location.reload(true);
-               }
+       current_analysis_xhr = new AbortController();
+       const signal = current_analysis_xhr.signal;
+       fetch(backend_url + "?ims=" + ims + "&unique=" + unique, { signal })
+               .then((response) => response.json().then(data => ({ok: response.ok, headers: response.headers, json: data})))  // ick
+               .then((obj) => {
+                       if (!obj.ok) {
+                               handle_err();
+                               return;
+                       }
 
-               // Verify that the PV makes sense.
-               var valid = true;
-               if (new_data['pv']) {
-                       var hiddenboard = new Chess(new_data['position']['fen']);
-                       for (var i = 0; i < new_data['pv'].length; ++i) {
-                               if (hiddenboard.move(new_data['pv'][i]) === null) {
-                                       valid = false;
-                                       break;
-                               }
+                       if (delay_ms === 0) {
+                               process_update_response(obj.json, obj.headers);
+                       } else {
+                               setTimeout(function() { process_update_response(obj.json, obj.headers); }, delay_ms);
                        }
-               }
 
-               var timeout = 100;
-               if (valid) {
-                       possibly_play_sound(current_analysis_data, new_data);
-                       current_analysis_data = new_data;
-                       update_board();
-                       update_num_viewers(num_viewers);
-               } else {
-                       console.log("Received invalid update, waiting five seconds and trying again.");
-                       setTimeout(function() { location.reload(true); }, 5000);
-               }
+                       // Next update.
+                       if (!backend_url.match(/history/)) {
+                               let timeout = 100;
+                               current_analysis_request_timer = setTimeout(function() { request_update(); }, timeout);
+                       }
+               })
+               .catch((err) => {
+                       if (err.name === 'AbortError') {
+                               // Aborted because we are switching backends. Abandon and don't retry,
+                               // because another one is already started for us.
+                       } else {
+                               console.log(err);
+                               handle_err(err);
+                       }
+               })
+               .finally(() => {
+                       // Display.
+                       document.body.style.opacity = null;
+               })
 
-               // Next update.
-               if (!backend_url.match(/history/)) {
-                       current_analysis_request_timer = setTimeout(function() { request_update(); }, timeout);
-               }
-       }).fail(function(jqXHR, textStatus, errorThrown) {
-               if (textStatus === "abort") {
-                       // Aborted because we are switching backends. Abandon and don't retry,
-                       // because another one is already started for us.
-               } else {
-                       // Backend error or similar. Wait ten seconds, then try again.
-                       current_analysis_request_timer = setTimeout(function() { request_update(); }, 10000);
+}
+
+function process_update_response(data, headers) {
+       sync_server_clock(headers.get('Date'));
+       ims = headers.get('X-RGLM');
+       let num_viewers = headers.get('X-RGNV');
+       let new_data;
+       if (Array.isArray(data)) {
+               new_data = JSON.parse(JSON.stringify(current_analysis_data));
+               JSON_delta.patch(new_data, data);
+       } else {
+               new_data = data;
+       }
+
+       let minimum_version = headers.get('X-RGMV');
+       if (minimum_version && minimum_version > SCRIPT_VERSION) {
+               // Upgrade to latest version with a force-reload.
+               location.reload(true);
+       }
+
+       // Verify that the PV makes sense.
+       let valid = true;
+       if (new_data['pv']) {
+               let hiddenboard = new Chess(new_data['position']['fen']);
+               for (let i = 0; i < new_data['pv'].length; ++i) {
+                       if (hiddenboard.move(new_data['pv'][i]) === null) {
+                               valid = false;
+                               break;
+                       }
                }
-       });
+       }
+
+       if (valid) {
+               possibly_play_sound(current_analysis_data, new_data);
+               current_analysis_data = new_data;
+               update_board();
+               update_num_viewers(num_viewers);
+       } else {
+               console.log("Received invalid update, waiting five seconds and trying again.");
+               setTimeout(function() { location.reload(true); }, 5000);
+       }
 }
 
-var possibly_play_sound = function(old_data, new_data) {
+function possibly_play_sound(old_data, new_data) {
        if (!enable_sound) {
                return;
        }
        if (old_data === null) {
                return;
        }
-       var ding = document.getElementById('ding');
+       let ding = document.getElementById('ding');
        if (ding && ding.play) {
                if (old_data['position'] && old_data['position']['fen'] &&
                    new_data['position'] && new_data['position']['fen'] &&
-                   (old_data['position']['fen'] !== new_data['position']['fen'] ||
-                    old_data['position']['move_num'] !== new_data['position']['move_num'])) {
+                   old_data['position']['fen'] !== new_data['position']['fen']) {
                        ding.play();
                }
        }
@@ -333,10 +380,10 @@ var possibly_play_sound = function(old_data, new_data) {
 /**
  * @type {!string} server_date_string
  */
-var sync_server_clock = function(server_date_string) {
-       var server_time_ms = new Date(server_date_string).getTime();
-       var client_time_ms = new Date().getTime();
-       var estimated_offset_ms = server_time_ms - client_time_ms;
+function sync_server_clock(server_date_string) {
+       let server_time_ms = new Date(server_date_string).getTime();
+       let client_time_ms = new Date().getTime();
+       let estimated_offset_ms = server_time_ms - client_time_ms;
 
        // In order not to let the noise move us too much back and forth
        // (the server only has one-second resolution anyway), we only
@@ -347,33 +394,60 @@ var sync_server_clock = function(server_date_string) {
        }
 }
 
-var clear_arrows = function() {
-       for (var i = 0; i < arrows.length; ++i) {
+function clear_arrows() {
+       for (let i = 0; i < arrows.length; ++i) {
                if (arrows[i].svg) {
-                       if (arrows[i].svg.parentElement) {
-                               arrows[i].svg.parentElement.removeChild(arrows[i].svg);
-                       }
+                       arrows[i].svg.remove();
                        delete arrows[i].svg;
                }
        }
        arrows = [];
 
        occupied_by_arrows = [];
-       for (var y = 0; y < 8; ++y) {
+       for (let y = 0; y < 8; ++y) {
                occupied_by_arrows.push([false, false, false, false, false, false, false, false]);
        }
 }
 
-var redraw_arrows = function() {
-       for (var i = 0; i < arrows.length; ++i) {
+function redraw_arrows() {
+       for (let i = 0; i < arrows.length; ++i) {
                position_arrow(arrows[i]);
        }
 }
 
+/** @param {!string} fen
+ * @return {!string}
+ *
+ * Return whose side it is to play (w or b), given a FEN.
+ */
+function find_toplay(fen) {
+       return fen.split(' ')[1];
+}
+
+/** @param {!string} fen
+ * @return {!number}
+ *
+ * Return the move clock, starting from 1. See also find_toplay().
+ */
+function find_move_num(fen) {
+       return parseInt(fen.split(' ')[5]);
+}
+
+/** @param {!string} fen
+ * @return {!number}
+ *
+ * Return the half-move clock, starting from 0 (and never resetting).
+ */
+function find_halfmove_num(fen) {
+       let move_num = find_move_num(fen);
+       let toplay = find_toplay(fen);
+       return (move_num - 1) * 2 + (toplay === 'w' ? 0 : 1);
+}
+
 /** @param {!number} x
  * @return {!number}
  */
-var sign = function(x) {
+function sign(x) {
        if (x > 0) {
                return 1;
        } else if (x < 0) {
@@ -388,11 +462,11 @@ var sign = function(x) {
  * @param {!string} to The square the arrow is to (e.g. e4).
  * @return {boolean}
  */
-var interfering_arrow = function(from, to) {
-       var from_col = from.charCodeAt(0) - "a1".charCodeAt(0);
-       var from_row = from.charCodeAt(1) - "a1".charCodeAt(1);
-       var to_col   = to.charCodeAt(0) - "a1".charCodeAt(0);
-       var to_row   = to.charCodeAt(1) - "a1".charCodeAt(1);
+function interfering_arrow(from, to) {
+       let from_col = from.charCodeAt(0) - "a1".charCodeAt(0);
+       let from_row = from.charCodeAt(1) - "a1".charCodeAt(1);
+       let to_col   = to.charCodeAt(0) - "a1".charCodeAt(0);
+       let to_row   = to.charCodeAt(1) - "a1".charCodeAt(1);
 
        occupied_by_arrows[from_row][from_col] = true;
 
@@ -403,10 +477,10 @@ var interfering_arrow = function(from, to) {
        }
 
        // Sliding piece: Check if anything except the from-square is seen before.
-       var dx = sign(to_col - from_col);
-       var dy = sign(to_row - from_row);
-       var x = from_col;
-       var y = from_row;
+       let dx = sign(to_col - from_col);
+       let dy = sign(to_row - from_row);
+       let x = from_col;
+       let y = from_row;
        do {
                x += dx;
                y += dy;
@@ -429,16 +503,16 @@ var interfering_arrow = function(from, to) {
  * @param {!number} u
  * @return {!string} The point in "x y" form, suitable for SVG paths.
  */
-var point_from_start = function(x1, y1, x2, y2, t, u) {
-       var dx = x2 - x1;
-       var dy = y2 - y1;
+function point_from_start(x1, y1, x2, y2, t, u) {
+       let dx = x2 - x1;
+       let dy = y2 - y1;
 
-       var norm = 1.0 / Math.sqrt(dx * dx + dy * dy);
+       let norm = 1.0 / Math.sqrt(dx * dx + dy * dy);
        dx *= norm;
        dy *= norm;
 
-       var x = x1 + dx * t + dy * u;
-       var y = y1 + dy * t - dx * u;
+       let x = x1 + dx * t + dy * u;
+       let y = y1 + dy * t - dx * u;
        return x + " " + y;
 }
 
@@ -452,20 +526,20 @@ var point_from_start = function(x1, y1, x2, y2, t, u) {
  * @param {!number} u
  * @return {!string} The point in "x y" form, suitable for SVG paths.
  */
-var point_from_end = function(x1, y1, x2, y2, t, u) {
-       var dx = x2 - x1;
-       var dy = y2 - y1;
+function point_from_end(x1, y1, x2, y2, t, u) {
+       let dx = x2 - x1;
+       let dy = y2 - y1;
 
-       var norm = 1.0 / Math.sqrt(dx * dx + dy * dy);
+       let norm = 1.0 / Math.sqrt(dx * dx + dy * dy);
        dx *= norm;
        dy *= norm;
 
-       var x = x2 + dx * t + dy * u;
-       var y = y2 + dy * t - dx * u;
+       let x = x2 + dx * t + dy * u;
+       let y = y2 + dy * t - dx * u;
        return x + " " + y;
 }
 
-var position_arrow = function(arrow) {
+function position_arrow(arrow) {
        if (arrow.svg) {
                if (arrow.svg.parentElement) {
                        arrow.svg.parentElement.removeChild(arrow.svg);
@@ -476,44 +550,41 @@ var position_arrow = function(arrow) {
                return;
        }
 
-       var zoom_factor = $("#board").width() / 400.0;
-       var line_width = arrow.line_width * zoom_factor;
-       var arrow_size = arrow.arrow_size * zoom_factor;
+       // We always draw as if the board is 400x400, the viewBox will adjust that for us
+       let line_width = arrow.line_width;
+       let arrow_size = arrow.arrow_size;
 
-       var square_width = $(".square-a8").width();
-       var pos, from_y, to_y, from_x, to_x;
+       let square_width = 400 / 8;
+       let from_y, to_y, from_x, to_x;
        if (board.orientation() === 'black') {
-               pos = $(".square-h1").position();
                from_y = (arrow.from_row + 0.5)*square_width;
                to_y = (arrow.to_row + 0.5)*square_width;
                from_x = (7 - arrow.from_col + 0.5)*square_width;
                to_x = (7 - arrow.to_col + 0.5)*square_width;
        } else {
-               pos = $(".square-a8").position();
                from_y = (7 - arrow.from_row + 0.5)*square_width;
                to_y = (7 - arrow.to_row + 0.5)*square_width;
                from_x = (arrow.from_col + 0.5)*square_width;
                to_x = (arrow.to_col + 0.5)*square_width;
        }
 
-       var SVG_NS = "http://www.w3.org/2000/svg";
-       var XHTML_NS = "http://www.w3.org/1999/xhtml";
-       var svg = document.createElementNS(SVG_NS, "svg");
-       svg.setAttribute("width", /** @type{number} */ ($("#board").width()));
-       svg.setAttribute("height", /** @type{number} */ ($("#board").height()));
-       svg.setAttribute("style", "position: absolute");
-       svg.setAttribute("position", "absolute");
+       let SVG_NS = "http://www.w3.org/2000/svg";
+       let XHTML_NS = "http://www.w3.org/1999/xhtml";
+       let svg = document.createElementNS(SVG_NS, "svg");
+       svg.setAttribute("width", "100%");
+       svg.setAttribute("height", "100%");
+       svg.setAttribute("viewBox", "0 0 400 400");
        svg.setAttribute("version", "1.1");
        svg.setAttribute("class", "c1");
        svg.setAttribute("xmlns", XHTML_NS);
 
-       var x1 = from_x;
-       var y1 = from_y;
-       var x2 = to_x;
-       var y2 = to_y;
+       let x1 = from_x;
+       let y1 = from_y;
+       let x2 = to_x;
+       let y2 = to_y;
 
        // Draw the line.
-       var outline = document.createElementNS(SVG_NS, "path");
+       let outline = document.createElementNS(SVG_NS, "path");
        outline.setAttribute("d", "M " + point_from_start(x1, y1, x2, y2, arrow_size / 2, 0) + " L " + point_from_end(x1, y1, x2, y2, -arrow_size / 2, 0));
        outline.setAttribute("xmlns", XHTML_NS);
        outline.setAttribute("stroke", "#666");
@@ -521,7 +592,7 @@ var position_arrow = function(arrow) {
        outline.setAttribute("fill", "none");
        svg.appendChild(outline);
 
-       var path = document.createElementNS(SVG_NS, "path");
+       let path = document.createElementNS(SVG_NS, "path");
        path.setAttribute("d", "M " + point_from_start(x1, y1, x2, y2, arrow_size / 2, 0) + " L " + point_from_end(x1, y1, x2, y2, -arrow_size / 2, 0));
        path.setAttribute("xmlns", XHTML_NS);
        path.setAttribute("stroke", arrow.fg_color);
@@ -530,7 +601,7 @@ var position_arrow = function(arrow) {
        svg.appendChild(path);
 
        // Then the arrow head.
-       var head = document.createElementNS(SVG_NS, "path");
+       let head = document.createElementNS(SVG_NS, "path");
        head.setAttribute("d",
                "M " +  point_from_end(x1, y1, x2, y2, 0, 0) +
                " L " + point_from_end(x1, y1, x2, y2, -arrow_size, -arrow_size / 2) +
@@ -543,8 +614,11 @@ var position_arrow = function(arrow) {
        head.setAttribute("fill", arrow.fg_color);
        svg.appendChild(head);
 
-       $(svg).css({ top: pos.top, left: pos.left, 'pointer-events': 'none' });
-       document.body.appendChild(svg);
+       svg.style.position = 'absolute';
+       svg.style.top = '0px';  /* Border for .board-b72b1. */
+       svg.style.left = '0px';
+       svg.style.pointerEvents = 'none';
+       document.getElementById('board').appendChild(svg);
        arrow.svg = svg;
 }
 
@@ -555,14 +629,14 @@ var position_arrow = function(arrow) {
  * @param {number} line_width
  * @param {number} arrow_size
  */
-var create_arrow = function(from_square, to_square, fg_color, line_width, arrow_size) {
-       var from_col = from_square.charCodeAt(0) - "a1".charCodeAt(0);
-       var from_row = from_square.charCodeAt(1) - "a1".charCodeAt(1);
-       var to_col   = to_square.charCodeAt(0) - "a1".charCodeAt(0);
-       var to_row   = to_square.charCodeAt(1) - "a1".charCodeAt(1);
+function create_arrow(from_square, to_square, fg_color, line_width, arrow_size) {
+       let from_col = from_square.charCodeAt(0) - "a1".charCodeAt(0);
+       let from_row = from_square.charCodeAt(1) - "a1".charCodeAt(1);
+       let to_col   = to_square.charCodeAt(0) - "a1".charCodeAt(0);
+       let to_row   = to_square.charCodeAt(1) - "a1".charCodeAt(1);
 
        // Create arrow.
-       var arrow = {
+       let arrow = {
                from_col: from_col,
                from_row: from_row,
                to_col: to_col,
@@ -576,9 +650,9 @@ var create_arrow = function(from_square, to_square, fg_color, line_width, arrow_
        arrows.push(arrow);
 }
 
-var compare_by_score = function(refutation_lines, invert, a, b) {
-       var sa = compute_score_sort_key(refutation_lines[b]['score'], refutation_lines[b]['depth'], invert);
-       var sb = compute_score_sort_key(refutation_lines[a]['score'], refutation_lines[a]['depth'], invert);
+function compare_by_score(refutation_lines, invert, a, b) {
+       let sa = compute_score_sort_key(refutation_lines[b]['score'], refutation_lines[b]['depth'], invert);
+       let sb = compute_score_sort_key(refutation_lines[a]['score'], refutation_lines[a]['depth'], invert);
        return sa - sb;
 }
 
@@ -593,15 +667,15 @@ var compare_by_score = function(refutation_lines, invert, a, b) {
  * @return {Array.<string>} The FEN representation (e.g. Ne4) of all
  *     moves, in score order.
  */
-var find_nonstupid_moves = function(data, margin, invert) {
+function find_nonstupid_moves(data, margin, invert) {
        // First of all, if there are any moves that are more than 0.5 ahead of
        // the primary move, the refutation lines are probably bunk, so just
        // kill them all. 
-       var best_score = undefined;
-       var pv_score = undefined;
-       for (var move in data['refutation_lines']) {
-               var line = data['refutation_lines'][move];
-               var score = compute_score_sort_key(line['score'], line['depth'], invert, false);
+       let best_score = undefined;
+       let pv_score = undefined;
+       for (let move in data['refutation_lines']) {
+               let line = data['refutation_lines'][move];
+               let score = compute_score_sort_key(line['score'], line['depth'], invert);
                if (move == data['pv'][0]) {
                        pv_score = score;
                }
@@ -619,15 +693,16 @@ var find_nonstupid_moves = function(data, margin, invert) {
 
        // Now find all moves that are within “margin” of the best score.
        // The PV move will always be first.
-       var moves = [];
-       for (var move in data['refutation_lines']) {
-               var line = data['refutation_lines'][move];
-               var score = compute_score_sort_key(line['score'], line['depth'], invert);
+       let moves = [];
+       for (let move in data['refutation_lines']) {
+               let line = data['refutation_lines'][move];
+               let score = compute_score_sort_key(line['score'], line['depth'], invert);
                if (move != data['pv'][0] && best_score - score <= margin) {
                        moves.push(move);
                }
        }
-       moves = moves.sort(function(a, b) { return compare_by_score(data['refutation_lines'], data['position']['toplay'] === 'B', a, b) });
+       let toplay = find_toplay(data['position']['fen']);
+       moves = moves.sort(function(a, b) { return compare_by_score(data['refutation_lines'], toplay, a, b) });
        moves.unshift(data['pv'][0]);
 
        return moves;
@@ -637,30 +712,26 @@ var find_nonstupid_moves = function(data, margin, invert) {
  * @param {number} x
  * @return {!string}
  */
-var thousands = function(x) {
+function thousands(x) {
        return String(x).split('').reverse().join('').replace(/(\d{3}\B)/g, '$1,').split('').reverse().join('');
 }
 
 /**
  * @param {!string} start_fen
  * @param {Array.<string>} pv
- * @param {number} move_num
- * @param {!string} toplay
- * @param {Array<{ first_move: integer, score: Object }>} scores
+ * @param {Array<{ first_move: number, score: Object }>} scores
  * @param {number} start_display_move_num
  * @param {number=} opt_limit
  * @param {boolean=} opt_showlast
  */
-var add_pv = function(start_fen, pv, move_num, toplay, scores, start_display_move_num, opt_limit, opt_showlast) {
+function add_pv(start_fen, pv, scores, start_display_move_num, opt_limit, opt_showlast) {
        display_lines.push({
                start_fen: start_fen,
                pv: pv,
-               move_num: parseInt(move_num),
-               toplay: toplay,
                scores: scores,
                start_display_move_num: start_display_move_num
        });
-       var splicepos = null;
+       let splicepos = null;
        if (scores !== null && scores.length >= 1 &&
            scores[scores.length - 1].score !== undefined &&
            scores[scores.length - 1].score !== null &&
@@ -677,217 +748,235 @@ var add_pv = function(start_fen, pv, move_num, toplay, scores, start_display_mov
  * @param {number=} opt_limit If set, show at most this number of moves.
  * @param {boolean=} opt_showlast If limit is set, show the last moves instead of the first ones.
  */
-var print_pv = function(line_num, splicepos, opt_limit, opt_showlast) {
-       var display_line = display_lines[line_num];
-       var pv = display_line.pv;
-       var move_num = display_line.move_num;
-       var toplay = display_line.toplay;
+function print_pv(line_num, splicepos, opt_limit, opt_showlast) {
+       let display_line = display_lines[line_num];
+       let pv = display_line.pv;
+       let halfmove_num = find_halfmove_num(display_line.start_fen) + 2;  // From two, for simplicity.
+       let start_halfmove_num = halfmove_num;
+
+       let ret = document.createDocumentFragment();
 
        // Truncate PV at the start if needed.
-       var start_display_move_num = display_line.start_display_move_num;
-       if (start_display_move_num > 0) {
-               pv = pv.slice(start_display_move_num);
-               var to_add = start_display_move_num;
-               if (toplay === 'B') {
-                       ++move_num;
-                       toplay = 'W';
-                       --to_add;
-               }
-               if (to_add % 2 == 1) {
-                       toplay = 'B';
-                       --to_add;
-               }
-               move_num += to_add / 2;
-               if (splicepos !== null && splicepos > 0) {
-                       --splicepos;
-               }
-       }
-
-       var ret = '';
-       var i = 0;
-       var in_tb = false;
-       if (opt_limit && opt_showlast && pv.length > opt_limit) {
-               // Truncate the PV at the beginning (instead of at the end).
-               // We assume here that toplay is 'W'. We also assume that if
-               // opt_showlast is set, then it is the history, and thus,
-               // the UI should be to expand the history.
-               ret = '(<a class="move" href="javascript:collapse_history(false)">…</a>) ';
-               i = pv.length - opt_limit;
-               if (i % 2 == 1) {
-                       ++i;
-               }
-               move_num += i / 2;
-       } else if (toplay == 'B' && pv.length > 0) {
-               var move = "";
-               if (splicepos === 0) {
-                       move += "(TB: ";
-                       in_tb = true;
+       let to_skip = display_line.start_display_move_num;
+       if (opt_limit && opt_showlast && pv.length - to_skip > opt_limit) {
+               // Explicit (UI-visible) truncation from the start, for the history.
+               ret.appendChild(document.createTextNode('('));
+               let link = document.createElement('a');
+               link.className = 'move';
+               link.href = 'javascript:collapse_history(false)';
+               link.textContent = '…';
+               ret.appendChild(link);
+               ret.appendChild(document.createTextNode(') '));
+               to_skip = pv.length - opt_limit;
+               to_skip += to_skip % 2;  // Make sure it starts on a white move.
+       }
+       if (to_skip > 0) {
+               pv = pv.slice(to_skip);
+               halfmove_num += to_skip;
+               if (splicepos !== null) {
+                       splicepos -= to_skip;
+                       if (splicepos < 0) {
+                               splicepos = 0;
+                       }
                }
-               move += "<a class=\"move\" id=\"automove" + line_num + "-0\" href=\"javascript:show_line(" + line_num + ", " + 0 + ");\">" + pv[0] + "</a>";
-               ret = move_num + '. … ' + move;
-               toplay = 'W';
-               ++i;
-               ++move_num;
        }
-       for ( ; i < pv.length; ++i) {
-               var move = "<a class=\"move\" id=\"automove" + line_num + "-" + i + "\" href=\"javascript:show_line(" + line_num + ", " + i + ");\">" + pv[i] + "</a>";
+
+       // The initial move number needs to go before any (TB: …) marker.
+       if (halfmove_num % 2 == 1) {
+               // Black move.
+               ret.appendChild(document.createTextNode((halfmove_num - 1) / 2 + '. … '));
+       } else {
+               // White move.
+               ret.appendChild(document.createTextNode(halfmove_num / 2 + '. '));
+       }
+       let in_tb = false;
+       for (let i = 0; i < pv.length; ++i, ++halfmove_num) {
+               let prefix = '';
                if (splicepos === i) {
-                       ret += " (TB: ";
+                       prefix = '(TB:';
                        in_tb = true;
                }
 
-               if (toplay == 'W') {
+               if (halfmove_num % 2 == 0 && i != 0) {
                        if (i > opt_limit && !opt_showlast) {
                                if (in_tb) {
-                                       ret += ")";
+                                       prefix += ')';
                                }
-                               return ret + ' (…)';
-                       }
-                       if (ret != '') {
-                               ret += ' ';
+                               ret.appendChild(document.createTextNode(prefix + ' (…)'));
+                               return ret;
                        }
-                       ret += move_num + '. ' + move;
-                       ++move_num;
-                       toplay = 'B';
+                       prefix += ' ' + (halfmove_num / 2) + '. ';
                } else {
-                       ret += ' ' + move;
-                       toplay = 'W';
+                       prefix += ' ';
                }
+               ret.appendChild(document.createTextNode(prefix));
+
+               let link = document.createElement('a');
+               link.className = 'move';
+               link.setAttribute('id', 'automove' + line_num + '-' + (halfmove_num - start_halfmove_num));
+               link.textContent = pv[i];
+               link.href = 'javascript:show_line(' + line_num + ', ' + (halfmove_num - start_halfmove_num) + ');';
+               ret.appendChild(link);
        }
        if (in_tb) {
-               ret += ")";
+               ret.appendChild(document.createTextNode(')'));
        }
        return ret;
 }
 
 /** Update the highlighted to/from squares on the board.
- * Based on the global "highlight_from" and "highlight_to" variables.
+ * Based on the global "highlight_from" and "highlight_to" letiables.
  */
-var update_board_highlight = function() {
-       $("#board").find('.square-55d63').removeClass('nonuglyhighlight');
+function update_board_highlight() {
+       document.getElementById("board").querySelectorAll('.square-55d63').forEach((square) => square.classList.remove('nonuglyhighlight'));
        if ((current_display_line === null || current_display_line_is_history) &&
            highlight_from !== undefined && highlight_to !== undefined) {
-               $("#board").find('.square-' + highlight_from).addClass('nonuglyhighlight');
-               $("#board").find('.square-' + highlight_to).addClass('nonuglyhighlight');
+               document.getElementById("board").querySelector('.square-' + highlight_from).classList.add('nonuglyhighlight');
+               document.getElementById("board").querySelector('.square-' + highlight_to).classList.add('nonuglyhighlight');
        }
 }
 
-var update_history = function() {
+function update_history() {
+       let history = document.getElementById('history');
        if (display_lines[0] === null || display_lines[0].pv.length == 0) {
-               $("#history").html("No history");
+               history.textContent = 'No history';
        } else if (truncate_display_history) {
-               $("#history").html(print_pv(0, null, 8, true));
+               history.replaceChildren(print_pv(0, null, 8, true));
        } else {
-               $("#history").html(
-                       '(<a class="move" href="javascript:collapse_history(true)">collapse</a>) ' +
-                       print_pv(0, null));
+               history.textContent = '(';
+               let link = document.createElement('a');
+               link.className = 'move';
+               link.href = 'javascript:collapse_history(true)';
+               link.textContent = 'collapse';
+               history.appendChild(link);
+               history.appendChild(document.createTextNode(') '));
+               history.append(print_pv(0, null));
        }
 }
 
 /**
  * @param {!boolean} truncate_history
  */
-var collapse_history = function(truncate_history) {
+function collapse_history(truncate_history) {
        truncate_display_history = truncate_history;
        update_history();
 }
 window['collapse_history'] = collapse_history;
 
-/** Update the HTML display of multi-PV from the global "refutation_lines".
+function choose_displayed_refutation_lines() {
+       if (hash_refutation_lines) {
+               // If we're in hash exploration, that takes precedence.
+               return [hash_refutation_lines, hash_refutation_lines_base_fen];
+       } else {
+               let data = displayed_analysis_data || current_analysis_data;
+               return [data['refutation_lines'], data['position']['fen']];
+       }
+}
+
+/** Update the HTML display of multi-PV.
  *
  * Also recreates the global "display_lines".
  */
-var update_refutation_lines = function() {
-       if (base_fen === null) {
+function update_refutation_lines() {
+       const [refutation_lines, refutation_lines_base_fen] = choose_displayed_refutation_lines();
+       if (!refutation_lines) {
                return;
        }
        if (display_lines.length > 2) {
                // Truncate so that only the history and PV is left.
                display_lines = [ display_lines[0], display_lines[1] ];
        }
-       var tbl = $("#refutationlines");
-       tbl.empty();
+       let tbl = document.getElementById("refutationlines");
+       tbl.replaceChildren();
 
        if (display_lines.length < 2) {
+               // Update the move highlight, as we've rewritten all the HTML.
+               update_move_highlight();
                return;
        }
 
        // Find out where the lines start from.
-       var base_line = [];
-       var base_scores = display_lines[1].scores;
-       var start_display_move_num = 0;
+       let base_line = [];
+       let base_scores = display_lines[1].scores;
+       let start_display_move_num = 0;
        if (hash_refutation_lines) {
                base_line = current_display_line.pv.slice(0, current_display_move + 1);
                base_scores = current_display_line.scores;
                start_display_move_num = base_line.length;
        }
 
-       var moves = [];
-       for (var move in refutation_lines) {
+       let moves = [];
+       for (let move in refutation_lines) {
                moves.push(move);
        }
 
-       var invert = (toplay === 'B');
+       let invert = (find_toplay(refutation_lines_base_fen) === 'b');
        if (current_display_line && current_display_move % 2 == 0 && !current_display_line_is_history) {
                invert = !invert;
        }
        moves = moves.sort(function(a, b) { return compare_by_score(refutation_lines, invert, a, b) });
-       for (var i = 0; i < moves.length; ++i) {
-               var line = refutation_lines[moves[i]];
+       for (let i = 0; i < moves.length; ++i) {
+               let line = refutation_lines[moves[i]];
 
-               var tr = document.createElement("tr");
+               let tr = document.createElement("tr");
 
-               var move_td = document.createElement("td");
+               let move_td = document.createElement("td");
                tr.appendChild(move_td);
-               $(move_td).addClass("move");
+               move_td.classList.add("move");
 
-               var scores = base_scores.concat([{ first_move: start_display_move_num, score: line['score'] }]);
+               let scores = base_scores.concat([{ first_move: start_display_move_num, score: line['score'] }]);
 
                if (line['pv'].length == 0) {
                        // Not found, so just make a one-move PV.
-                       var move = "<a class=\"move\" href=\"javascript:show_line(" + display_lines.length + ", " + 0 + ");\">" + line['move'] + "</a>";
-                       $(move_td).html(move);
-                       var score_td = document.createElement("td");
-
-                       $(score_td).addClass("score");
-                       $(score_td).text("—");
+                       let link = document.createElement('a');
+                       link.className = 'move';
+                       link.href = 'javascript:show_line(' + display_lines.length + ', ' + 0 + ')';
+                       link.textContent = line['move'];
+                       move_td.replaceChildren(link);
+
+                       let score_td = document.createElement("td");
+                       score_td.classList.add("score");
+                       score_td.textContent = "—";
                        tr.appendChild(score_td);
 
-                       var depth_td = document.createElement("td");
+                       let depth_td = document.createElement("td");
                        tr.appendChild(depth_td);
-                       $(depth_td).addClass("depth");
-                       $(depth_td).text("—");
+                       depth_td.classList.add("depth");
+                       depth_td.textContent = "—";
 
-                       var pv_td = document.createElement("td");
+                       let pv_td = document.createElement("td");
                        tr.appendChild(pv_td);
-                       $(pv_td).addClass("pv");
-                       $(pv_td).html(add_pv(base_fen, base_line.concat([ line['move'] ]), move_num, toplay, scores, start_display_move_num));
+                       pv_td.classList.add("pv");
+                       pv_td.append(add_pv(refutation_lines_base_fen, base_line.concat([ line['move'] ]), scores, start_display_move_num));
 
                        tbl.append(tr);
                        continue;
                }
 
-               var move = "<a class=\"move\" href=\"javascript:show_line(" + display_lines.length + ", " + 0 + ");\">" + line['move'] + "</a>";
-               $(move_td).html(move);
+               let move_link = document.createElement("a");
+               move_link.classList.add("move");
+               move_link.setAttribute("href", "javascript:show_line(" + display_lines.length + ", 0)");
+               move_link.textContent = line['move'];
+               move_td.appendChild(move_link);
 
-               var score_td = document.createElement("td");
+               let score_td = document.createElement("td");
                tr.appendChild(score_td);
-               $(score_td).addClass("score");
-               $(score_td).text(format_short_score(line['score']));
+               score_td.classList.add("score");
+               score_td.textContent = format_short_score(line['score']);
 
-               var depth_td = document.createElement("td");
+               let depth_td = document.createElement("td");
                tr.appendChild(depth_td);
-               $(depth_td).addClass("depth");
+               depth_td.classList.add("depth");
                if (line['depth'] && line['depth'] >= 0) {
-                       $(depth_td).text("d" + line['depth']);
+                       depth_td.textContent = "d" + line['depth'];
                } else {
-                       $(depth_td).text("—");
+                       depth_td.textContent = "—";
                }
 
-               var pv_td = document.createElement("td");
+               let pv_td = document.createElement("td");
                tr.appendChild(pv_td);
-               $(pv_td).addClass("pv");
-               $(pv_td).html(add_pv(base_fen, base_line.concat(line['pv']), move_num, toplay, scores, start_display_move_num, 10));
+               pv_td.classList.add("pv");
+               pv_td.append(add_pv(refutation_lines_base_fen, base_line.concat(line['pv']), scores, start_display_move_num, 10));
 
                tbl.append(tr);
        }
@@ -904,12 +993,12 @@ var update_refutation_lines = function() {
  * @param {Array.<string>} moves
  * @param {number} last_move
  */
-var chess_from = function(fen, moves, last_move) {
-       var hiddenboard = new Chess();
+function chess_from(fen, moves, last_move) {
+       let hiddenboard = new Chess();
        if (fen !== null && fen !== undefined) {
                hiddenboard.load(fen);
        }
-       for (var i = 0; i <= last_move; ++i) {
+       for (let i = 0; i <= last_move; ++i) {
                if (moves[i] === '0-0') {
                        hiddenboard.move('O-O');
                } else if (moves[i] === '0-0-0') {
@@ -921,25 +1010,25 @@ var chess_from = function(fen, moves, last_move) {
        return hiddenboard;
 }
 
-var update_game_list = function(games) {
-       $("#games").text("");
+function update_game_list(games) {
+       document.getElementById("games").textContent = "";
        if (games === null) {
                return;
        }
 
-       var games_div = document.getElementById('games');
-       for (var game_num = 0; game_num < games.length; ++game_num) {
-               var game = games[game_num];
-               var game_span = document.createElement("span");
+       let games_div = document.getElementById('games');
+       for (let game_num = 0; game_num < games.length; ++game_num) {
+               let game = games[game_num];
+               let game_span = document.createElement("span");
                game_span.setAttribute("class", "game");
 
-               var game_name = document.createTextNode(game['name']);
+               let game_name = document.createTextNode(game['name']);
                if (game['url'] === backend_url) {
                        // This game.
                        game_span.appendChild(game_name);
 
                        if (current_analysis_data && current_analysis_data['position']) {
-                               var score;
+                               let score;
                                if (current_analysis_data['position']['result']) {
                                        score = " (" + current_analysis_data['position']['result'] + ")";
                                } else {
@@ -949,12 +1038,12 @@ var update_game_list = function(games) {
                        }
                } else {
                        // Some other game.
-                       var game_a = document.createElement("a");
+                       let game_a = document.createElement("a");
                        game_a.setAttribute("href", "#" + game['id']);
                        game_a.appendChild(game_name);
                        game_span.appendChild(game_a);
 
-                       var score;
+                       let score;
                        if (game['result']) {
                                score = " (" + game['result'] + ")";
                        } else {
@@ -971,11 +1060,11 @@ var update_game_list = function(games) {
  * Try to find a running game that matches with the current hash,
  * and switch to it if we're not already displaying it.
  */
-var possibly_switch_game_from_hash = function() {
-       var history_match = window.location.hash.match(/^#history=([a-zA-Z0-9_-]+)/);
+function possibly_switch_game_from_hash() {
+       let history_match = window.location.hash.match(/^#history=([a-zA-Z0-9_-]+)/);
        if (history_match !== null) {
-               var game_id = history_match[1];
-               var fake_game = {
+               let game_id = history_match[1];
+               let fake_game = {
                        url: '/history/' + game_id + '.json',
                        hashurl: '',
                        id: 'history=' + game_id
@@ -988,8 +1077,8 @@ var possibly_switch_game_from_hash = function() {
                return;
        }
 
-       var hash = window.location.hash.replace(/^#/,'');
-       for (var i = 0; i < current_games.length; ++i) {
+       let hash = window.location.hash.replace(/^#/,'');
+       for (let i = 0; i < current_games.length; ++i) {
                if (current_games[i]['id'] === hash) {
                        if (backend_url !== current_games[i]['url']) {
                                switch_backend(current_games[i]);
@@ -1003,14 +1092,14 @@ var possibly_switch_game_from_hash = function() {
  * If this is a Chess960 castling which doesn't move the king,
  * move the rook instead.
 */
-var patch_move = function(move) {
+function patch_move(move) {
        if (move === null) return null;
        if (move.from !== move.to) return move;
 
-       var f = move.rook_sq & 15;
-       var r = move.rook_sq >> 4;
-       var from = ('abcdefgh'.substring(f,f+1) + '87654321'.substring(r,r+1));
-       var to = move.to;
+       let f = move.rook_sq & 15;
+       let r = move.rook_sq >> 4;
+       let from = ('abcdefgh'.substring(f,f+1) + '87654321'.substring(r,r+1));
+       let to = move.to;
 
        if (move.to === 'g1') {
                to = 'f1';
@@ -1027,9 +1116,11 @@ var patch_move = function(move) {
 
 /** Update all the HTML on the page, based on current global state.
  */
-var update_board = function() {
-       var data = displayed_analysis_data || current_analysis_data;
-       var current_data = current_analysis_data;  // Convenience alias.
+function update_board() {
+       document.body.style.opacity = null;
+
+       let data = displayed_analysis_data || current_analysis_data;
+       let current_data = current_analysis_data;  // Convenience alias.
 
        display_lines = [];
 
@@ -1037,8 +1128,8 @@ var update_board = function() {
        // unconditionally taken from current_data (we're not interested in
        // historic history).
        if (current_data['position']['history']) {
-               var start = (current_data['position'] && current_data['position']['start_fen']) ? current_data['position']['start_fen'] : 'start';
-               add_pv(start, current_data['position']['history'], 1, 'W', null, 0, 8, true);
+               let start = (current_data['position'] && current_data['position']['start_fen']) ? current_data['position']['start_fen'] : 'rnbqkbnr/pppppppp/8/8/8/8/PPPPPPPP/RNBQKBNR w KQkq - 0 1';
+               add_pv(start, current_data['position']['history'], null, 0, 8, true);
        } else {
                display_lines.push(null);
        }
@@ -1055,7 +1146,7 @@ var update_board = function() {
 
        // The headline. Names are always fetched from current_data;
        // the rest can depend a bit.
-       var headline;
+       let headline;
        if (current_data &&
            current_data['position']['player_w'] && current_data['position']['player_b']) {
                headline = current_data['position']['player_w'] + '–' +
@@ -1064,51 +1155,42 @@ var update_board = function() {
                headline = 'Analysis';
        }
 
-       // Credits, where applicable. Note that we don't want the footer to change a lot
-       // when e.g. viewing history, so if any of these changed during the game,
-       // use the current one still.
-       if (current_data['using_lomonosov']) {
-               $("#lomonosov").show();
-       } else {
-               $("#lomonosov").hide();
-       }
-
        // Credits: The engine name/version.
        if (current_data['engine'] && current_data['engine']['name'] !== null) {
-               $("#engineid").text(current_data['engine']['name']);
+               document.getElementById("engineid").textContent = current_data['engine']['name'];
        }
 
        // Credits: The engine URL.
        if (current_data['engine'] && current_data['engine']['url']) {
-               $("#engineid").attr("href", current_data['engine']['url']);
+               document.getElementById("engineid").setAttribute("href", current_data['engine']['url']);
        } else {
-               $("#engineid").removeAttr("href");
+               document.getElementById("engineid").removeAttribute("href");
        }
 
        // Credits: Engine details.
        if (current_data['engine'] && current_data['engine']['details']) {
-               $("#enginedetails").text(" (" + current_data['engine']['details'] + ")");
+               document.getElementById("enginedetails").textContent = " (" + current_data['engine']['details'] + ")";
        } else {
-               $("#enginedetails").text("");
+               document.getElementById("enginedetails").textContent = "";
        }
 
        // Credits: Move source, possibly with URL.
        if (current_data['move_source'] && current_data['move_source_url']) {
-               $("#movesource").text("Moves provided by ");
-               var movesource_a = document.createElement("a");
+               document.getElementById("movesource").textContent = "Moves provided by ";
+               let movesource_a = document.createElement("a");
                movesource_a.setAttribute("href", current_data['move_source_url']);
-               var movesource_text = document.createTextNode(current_data['move_source']);
+               let movesource_text = document.createTextNode(current_data['move_source']);
                movesource_a.appendChild(movesource_text);
-               var movesource_period = document.createTextNode(".");
+               let movesource_period = document.createTextNode(".");
                document.getElementById("movesource").appendChild(movesource_a);
                document.getElementById("movesource").appendChild(movesource_period);
        } else if (current_data['move_source']) {
-               $("#movesource").text("Moves provided by " + current_data['move_source'] + ".");
+               document.getElementById("movesource").textContent = "Moves provided by " + current_data['move_source'] + ".";
        } else {
-               $("#movesource").text("");
+               document.getElementById("movesource").textContent = "";
        }
 
-       var last_move;
+       let last_move;
        if (displayed_analysis_data) {
                // Displaying some non-current position, pick out the last move
                // from the history. This will work even if the fetch failed.
@@ -1120,27 +1202,28 @@ var update_board = function() {
                }
        } else if (data['position']['last_move'] !== 'none') {
                // Find the previous move.
-               var previous_move_num, previous_toplay;
-               if (data['position']['toplay'] == 'B') {
-                       previous_move_num = data['position']['move_num'];
-                       previous_toplay = 'W';
+               let previous_move_num, previous_toplay;
+               let fen = data['position']['fen'];
+               if (find_toplay(fen) === 'b') {
+                       previous_move_num = find_move_num(fen);
+                       previous_toplay = 'w';
                } else {
-                       previous_move_num = data['position']['move_num'] - 1;
-                       previous_toplay = 'B';
+                       previous_move_num = find_move_num(fen) - 1;
+                       previous_toplay = 'b';
                }
 
                last_move = format_move_with_number(
                        data['position']['last_move'],
                        previous_move_num,
-                       previous_toplay == 'W');
+                       previous_toplay == 'w');
                headline += ' after ' + last_move;
        } else {
                last_move = null;
        }
-       $("#headline").text(headline);
+       document.getElementById("headline").textContent = headline;
 
        // The <title> contains a very brief headline.
-       var title_elems = [];
+       let title_elems = [];
        if (data['position'] && data['position']['result']) {
                title_elems.push(data['position']['result']);
        } else if (data['score']) {
@@ -1164,9 +1247,9 @@ var update_board = function() {
                // We don't have historic analysis for this position, but we
                // can reconstruct what the last move was by just replaying
                // from the start.
-               var position = (data['position'] && data['position']['start_fen']) ? data['position']['start_fen'] : null;
-               var hiddenboard = chess_from(position, current_display_line.pv, current_display_move);
-               var moves = hiddenboard.history({ verbose: true });
+               let position = (data['position'] && data['position']['start_fen']) ? data['position']['start_fen'] : null;
+               let hiddenboard = chess_from(position, current_display_line.pv, current_display_move);
+               let moves = hiddenboard.history({ verbose: true });
                last_move = moves.pop();
                highlight_from = last_move.from;
                highlight_to = last_move.to;
@@ -1176,14 +1259,13 @@ var update_board = function() {
        update_board_highlight();
 
        if (data['failed']) {
-               $("#score").text("No analysis for this move");
-               $("#pvtitle").text("PV:");
-               $("#pv").empty();
-               $("#searchstats").html("&nbsp;");
-               $("#refutationlines").empty();
-               $("#whiteclock").empty();
-               $("#blackclock").empty();
-               refutation_lines = [];
+               document.getElementById("score").textContent = "No analysis for this move";
+               document.getElementById("pvtitle").textContent = "PV:";
+               document.getElementById("pv").replaceChildren();
+               document.getElementById("searchstats").innerHTML = "&nbsp;";
+               document.getElementById("refutationlines").replaceChildren();
+               document.getElementById("whiteclock").replaceChildren();
+               document.getElementById("blackclock").replaceChildren();
                update_refutation_lines();
                clear_arrows();
                update_displayed_line();
@@ -1191,13 +1273,16 @@ var update_board = function() {
                return;
        }
 
+       if (clock_timer !== null) {
+               clearTimeout(clock_timer);
+       }
        update_clock();
 
        // The score.
        if (current_display_line && !current_display_line_is_history) {
-               var score;
+               let score;
                if (current_display_line.scores && current_display_line.scores.length > 0) {
-                       for (var i = 0; i < current_display_line.scores.length; ++i) {
+                       for (let i = 0; i < current_display_line.scores.length; ++i) {
                                if (current_display_move < current_display_line.scores[i].first_move) {
                                        break;
                                }
@@ -1205,21 +1290,19 @@ var update_board = function() {
                        }
                }
                if (score) {
-                       $("#score").text(format_long_score(score));
+                       document.getElementById("score").textContent = format_long_score(score);
                } else {
-                       $("#score").text("No score for this line");
+                       document.getElementById("score").textContent = "No score for this line";
                }
        } else if (data['score']) {
-               $("#score").text(format_long_score(data['score']));
+               document.getElementById("score").textContent = format_long_score(data['score']);
        }
 
        // The search stats.
        if (data['searchstats']) {
-               $("#searchstats").html(data['searchstats']);
-       } else if (data['tablebase'] == 1) {
-               $("#searchstats").text("Tablebase result");
+               document.getElementById("searchstats").textContent = data['searchstats'];
        } else if (data['nodes'] && data['nps'] && data['depth']) {
-               var stats = thousands(data['nodes']) + ' nodes, ' + thousands(data['nps']) + ' nodes/sec, depth ' + data['depth'] + ' ply';
+               let stats = thousands(data['nodes']) + ' nodes, ' + thousands(data['nps']) + ' nodes/sec, depth ' + data['depth'] + ' ply';
                if (data['seldepth']) {
                        stats += ' (' + data['seldepth'] + ' selective)';
                }
@@ -1231,9 +1314,12 @@ var update_board = function() {
                        }
                }
 
-               $("#searchstats").text(stats);
+               document.getElementById("searchstats").textContent = stats;
        } else {
-               $("#searchstats").text("");
+               document.getElementById("searchstats").textContent = "";
+       }
+       if (admin_password !== null) {
+               document.getElementById("searchstats").innerHTML += " | <span style=\"color: red;\">ADMIN MODE (if password is right) | <a href=\"javascript:undo_move()\">Undo move</a></span>";
        }
 
        // Update the board itself.
@@ -1241,20 +1327,21 @@ var update_board = function() {
        update_displayed_line();
 
        // Print the PV.
-       $("#pvtitle").text("PV:");
+       document.getElementById("pvtitle").textContent = "PV:";
 
-       var scores = [{ first_move: -1, score: data['score'] }];
-       $("#pv").html(add_pv(data['position']['fen'], data['pv'], data['position']['move_num'], data['position']['toplay'], scores, 0));
+       let scores = [{ first_move: -1, score: data['score'] }];
+       document.getElementById("pv").replaceChildren(add_pv(data['position']['fen'], data['pv'], scores, 0));
 
        // Update the PV arrow.
        clear_arrows();
+       let toplay = find_toplay(data['position']['fen']);
        if (data['pv'].length >= 1) {
-               var hiddenboard = new Chess(base_fen);
+               let hiddenboard = new Chess(base_fen);
 
                // draw a continuation arrow as long as it's the same piece
-               var last_to;
-               for (var i = 0; i < data['pv'].length; i += 2) {
-                       var move = patch_move(hiddenboard.move(data['pv'][i]));
+               let last_to;
+               for (let i = 0; i < data['pv'].length; i += 2) {
+                       let move = patch_move(hiddenboard.move(data['pv'][i]));
 
                        if ((i >= 2 && move.from != last_to) ||
                             interfering_arrow(move.from, move.to)) {
@@ -1265,10 +1352,10 @@ var update_board = function() {
                        hiddenboard.move(data['pv'][i + 1]);  // To keep continuity.
                }
 
-               var alt_moves = find_nonstupid_moves(data, 30, data['position']['toplay'] === 'B');
-               for (var i = 1; i < alt_moves.length && i < 3; ++i) {
+               let alt_moves = find_nonstupid_moves(data, 30, toplay === 'b');
+               for (let i = 1; i < alt_moves.length && i < 3; ++i) {
                        hiddenboard = new Chess(base_fen);
-                       var move = patch_move(hiddenboard.move(alt_moves[i]));
+                       let move = patch_move(hiddenboard.move(alt_moves[i]));
                        if (move !== null) {
                                create_arrow(move.from, move.to, '#f66', 1, 10);
                        }
@@ -1277,14 +1364,11 @@ var update_board = function() {
 
        // See if all semi-reasonable moves have only one possible response.
        if (data['pv'].length >= 2) {
-               var nonstupid_moves = find_nonstupid_moves(data, 300, data['position']['toplay'] === 'B');
-               var response;
-               {
-                       var hiddenboard = new Chess(base_fen);
-                       hiddenboard.move(data['pv'][0]);
-                       response = hiddenboard.move(data['pv'][1]);
-               }
-               for (var i = 0; i < nonstupid_moves.length; ++i) {
+               let nonstupid_moves = find_nonstupid_moves(data, 300, toplay === 'b');
+               let hiddenboard = new Chess(base_fen);
+               hiddenboard.move(data['pv'][0]);
+               let response = hiddenboard.move(data['pv'][1]);
+               for (let i = 0; i < nonstupid_moves.length; ++i) {
                        if (nonstupid_moves[i] == data['pv'][0]) {
                                // ignore the PV move for refutation lines.
                                continue;
@@ -1297,10 +1381,10 @@ var update_board = function() {
                                response = undefined;
                                break;
                        }
-                       var line = data['refutation_lines'][nonstupid_moves[i]];
+                       let line = data['refutation_lines'][nonstupid_moves[i]];
                        hiddenboard = new Chess(base_fen);
                        hiddenboard.move(line['pv'][0]);
-                       var this_response = hiddenboard.move(line['pv'][1]);
+                       let this_response = hiddenboard.move(line['pv'][1]);
                        if (this_response === null) {
                                console.log("BUG: ", i);
                                console.log(data);
@@ -1318,49 +1402,44 @@ var update_board = function() {
                }
        }
 
-       // Update the refutation lines.
        base_fen = data['position']['fen'];
-       move_num = parseInt(data['position']['move_num']);
-       toplay = data['position']['toplay'];
-       refutation_lines = hash_refutation_lines || data['refutation_lines'];
        update_refutation_lines();
 
        // Update the sparkline last, since its size depends on how everything else reflowed.
        update_sparkline(data);
 }
 
-var update_sparkline = function(data) {
+function update_sparkline(data) {
+       let scorespark = document.getElementById('scoresparkcontainer');
+       scorespark.textContent = '';
        if (data && data['score_history']) {
-               var first_move_num = undefined;
-               for (var halfmove_num in data['score_history']) {
+               let first_move_num = undefined;
+               for (let halfmove_num in data['score_history']) {
                        halfmove_num = parseInt(halfmove_num);
                        if (first_move_num === undefined || halfmove_num < first_move_num) {
                                first_move_num = halfmove_num;
                        }
                }
                if (first_move_num !== undefined) {
-                       var last_move_num = data['position']['move_num'] * 2 - 3;
-                       if (data['position']['toplay'] === 'B') {
+                       let fen = data['position']['fen'];
+                       let last_move_num = find_move_num(fen) * 2 - 3;
+                       if (find_toplay(fen) === 'b') {
                                ++last_move_num;
                        }
 
                        // Possibly truncate some moves if we don't have enough width.
-                       // FIXME: Sometimes width() for #scorecontainer (and by extent,
-                       // #scoresparkcontainer) on Chrome for mobile seems to start off
-                       // at something very small, and then suddenly snap back into place.
-                       // Figure out why.
-                       var max_moves = Math.floor($("#scoresparkcontainer").width() / 5) - 5;
+                       let max_moves = Math.floor(scorespark.getBoundingClientRect().width / 5) - 3;
                        if (last_move_num - first_move_num > max_moves) {
                                first_move_num = last_move_num - max_moves;
                        }
 
-                       var min_score = -100;
-                       var max_score = 100;
-                       var last_score = null;
-                       var scores = [];
-                       for (var halfmove_num = first_move_num; halfmove_num <= last_move_num; ++halfmove_num) {
+                       let min_score = -1;
+                       let max_score = 1;
+                       let last_score = null;
+                       let scores = [];
+                       for (let halfmove_num = first_move_num; halfmove_num <= last_move_num; ++halfmove_num) {
                                if (data['score_history'][halfmove_num]) {
-                                       var score = compute_plot_score(data['score_history'][halfmove_num]);
+                                       let score = compute_plot_score(data['score_history'][halfmove_num]);
                                        last_score = score;
                                        if (score < min_score) min_score = score;
                                        if (score > max_score) max_score = score;
@@ -1368,43 +1447,94 @@ var update_sparkline = function(data) {
                                scores.push(last_score);
                        }
                        if (data['score']) {
-                               scores.push(compute_plot_score(data['score']));
+                               let score = compute_plot_score(data['score']);
+                               scores.push(score);
+                               if (score < min_score) min_score = score;
+                               if (score > max_score) max_score = score;
+                       }
+                       if (max_score - min_score < 100) {
+                               if (Math.abs(max_score) >= Math.abs(min_score)) {
+                                       max_score = min_score + 100;
+                               } else {
+                                       min_score = max_score - 100;
+                               }
                        }
-                       // FIXME: at some widths, calling sparkline() seems to push
-                       // #scorecontainer under the board.
-                       $('#scorespark').unbind('sparklineClick');
-                       $("#scorespark").sparkline(scores, {
-                               type: 'bar',
-                               zeroColor: 'gray',
-                               chartRangeMin: min_score,
-                               chartRangeMax: max_score,
-                               tooltipFormatter: function(sparkline, options, fields) {
-                                       // score_history contains the Nth _position_, but format_tooltip
-                                       // wants to format the Nth _move_; thus the -1.
-                                       return format_tooltip(data, fields[0].offset + first_move_num - 1);
+
+                       const h = scorespark.getBoundingClientRect().height;
+
+                       let base_y = h - h * min_score / (min_score - max_score);
+                       for (let i = 0; i < scores.length; ++i) {
+                               let rect = document.createElementNS('http://www.w3.org/2000/svg', 'rect');
+                               //rect.setAttributeNS(null, 'stroke', "#000000");
+                               rect.setAttributeNS(null, 'x', i * 5)
+                               rect.setAttributeNS(null, 'width', 4);
+                               let extent = scores[i] * h / (max_score - min_score);
+                               if (extent > 0 && extent < 1) {
+                                       extent = 1;
+                               } else if (extent < 0 && extent > -1) {
+                                       extent = -1;
                                }
-                       });
-                       $('#scorespark').unbind('sparklineClick');
-                       $('#scorespark').bind('sparklineClick', function(event) {
-                               var sparkline = event.sparklines[0];
-                               var region = sparkline.getCurrentRegionFields();
-                               if (region[0].offset !== undefined) {
-                                       show_line(0, first_move_num + region[0].offset - 1);
+
+                               let color;
+                               if (scores[i] === 0) {
+                                       color = [0.5, 0.5, 0.5];
+                                       rect.setAttributeNS(null, 'y', base_y);
+                                       rect.setAttributeNS(null, 'height', 1);
+                               } else if (scores[i] > 0) {
+                                       color = [0.2, 0.4, 0.8];
+                                       rect.setAttributeNS(null, 'y', base_y - extent);
+                                       rect.setAttributeNS(null, 'height', extent + 1);
+                               } else {
+                                       color = [1.0, 0.267, 0.267];
+                                       rect.setAttributeNS(null, 'y', base_y);
+                                       rect.setAttributeNS(null, 'height', -extent + 1);
                                }
-                       });
-               } else {
-                       $("#scorespark").text("");
+                               let hlcolor = [color[0], color[1], color[2]];
+                               if (scores[i] !== 0) { 
+                                       hlcolor[0] = Math.min(hlcolor[0] * 1.4, 1.0);
+                                       hlcolor[1] = Math.min(hlcolor[1] * 1.4, 1.0);
+                                       hlcolor[2] = Math.min(hlcolor[2] * 1.4, 1.0);
+                               }
+                               rect.style.fill = 'rgb(' + color[0]*100.0 + '%, ' + color[1]*100.0 + '%, ' + color[2]*100.0 + '%)';
+
+                               // score_history contains the Nth _position_, but format_tooltip
+                               // wants to format the Nth _move_; thus the -1.
+                               const tooltip = format_tooltip(data, i + first_move_num - 1);
+                               rect.addEventListener('mouseenter', (e) => draw_hover(e, hlcolor, tooltip));
+                               rect.addEventListener('mousemove', (e) => draw_hover(e, hlcolor, tooltip));
+                               rect.addEventListener('mouseleave', (e) => hide_hover(e, color));
+                               rect.addEventListener('click', (e) => { hide_hover(e, color); show_line(0, i + first_move_num - 1) });
+                               scorespark.appendChild(rect);
+                       }
                }
-       } else {
-               $("#scorespark").text("");
        }
 }
 
+function draw_hover(e, color, tooltip) {
+       e.target.style.fill = 'rgb(' + color[0]*100.0 + '%, ' + color[1]*100.0 + '%, ' + color[2]*100.0 + '%)';
+
+       let hover = document.getElementById('sparklinehover');
+       hover.textContent = tooltip;
+       hover.style.display = 'initial';
+
+       let left = Math.max(e.pageX + 10, window.pageXOffset);
+       let top = Math.max(e.pageY - hover.getBoundingClientRect().height, window.pageYOffset);
+       left = Math.min(left, window.pageXOffset + document.documentElement.clientWidth - hover.getBoundingClientRect().width);
+
+       hover.style.left = left + 'px';
+       hover.style.top = top + 'px';
+
+}
+function hide_hover(e, color) {
+       e.target.style.fill = 'rgb(' + color[0]*100.0 + '%, ' + color[1]*100.0 + '%, ' + color[2]*100.0 + '%)';
+       document.getElementById('sparklinehover').style.display = 'none';
+}
+
 /**
  * @param {number} num_viewers
  */
-var update_num_viewers = function(num_viewers) {
-       var text = "";
+function update_num_viewers(num_viewers) {
+       let text = "";
        if (num_viewers === null) {
                text = "";
        } else if (num_viewers == 1) {
@@ -1413,48 +1543,48 @@ var update_num_viewers = function(num_viewers) {
                text = num_viewers + " current viewers";
        }
        if (display_fen !== null) {
-               var counter = Math.floor(display_fen.split(" ")[4] / 2);
+               let counter = Math.floor(display_fen.split(" ")[4] / 2);
                if (counter >= 20) {
                        text = text.replace("current ", "");
                        text += " | 50-move rule: " + counter;
                }
        }
-       $("#numviewers").text(text);
+       document.getElementById("numviewers").textContent = text;
 }
 
-var update_clock = function() {
-       clearTimeout(clock_timer);
+function update_clock() {
+       clock_timer = null;
 
-       var data = displayed_analysis_data || current_analysis_data;
+       let data = displayed_analysis_data || current_analysis_data;
        if (!data) return;
 
        if (data['position']) {
-               var result = data['position']['result'];
+               let result = data['position']['result'];
                if (result === '1-0') {
-                       $("#whiteclock").text("1");
-                       $("#blackclock").text("0");
-                       $("#whiteclock").removeClass("running-clock");
-                       $("#blackclock").removeClass("running-clock");
+                       document.getElementById("whiteclock").textContent = "1";
+                       document.getElementById("blackclock").textContent = "0";
+                       document.getElementById("whiteclock").classList.remove("running-clock");
+                       document.getElementById("blackclock").classList.remove("running-clock");
                        return;
                }
                if (result === '1/2-1/2') {
-                       $("#whiteclock").text("1/2");
-                       $("#blackclock").text("1/2");
-                       $("#whiteclock").removeClass("running-clock");
-                       $("#blackclock").removeClass("running-clock");
+                       document.getElementById("whiteclock").textContent = "1/2";
+                       document.getElementById("blackclock").textContent = "1/2";
+                       document.getElementById("whiteclock").classList.remove("running-clock");
+                       document.getElementById("blackclock").classList.remove("running-clock");
                        return;
                }       
                if (result === '0-1') {
-                       $("#whiteclock").text("0");
-                       $("#blackclock").text("1");
-                       $("#whiteclock").removeClass("running-clock");
-                       $("#blackclock").removeClass("running-clock");
+                       document.getElementById("whiteclock").textContent = "0";
+                       document.getElementById("blackclock").textContent = "1";
+                       document.getElementById("whiteclock").classList.remove("running-clock");
+                       document.getElementById("blackclock").classList.remove("running-clock");
                        return;
                }
        }
 
-       var white_clock_ms = null;
-       var black_clock_ms = null;
+       let white_clock_ms = null;
+       let black_clock_ms = null;
 
        // Static clocks.
        if (data['position'] &&
@@ -1465,22 +1595,22 @@ var update_clock = function() {
        }
 
        // Dynamic clock (only one, obviously).
-       var color;
+       let color;
        if (data['position']['white_clock_target']) {
                color = "white";
-               $("#whiteclock").addClass("running-clock");
-               $("#blackclock").removeClass("running-clock");
+               document.getElementById("whiteclock").classList.add("running-clock");
+               document.getElementById("blackclock").classList.remove("running-clock");
        } else if (data['position']['black_clock_target']) {
                color = "black";
-               $("#whiteclock").removeClass("running-clock");
-               $("#blackclock").addClass("running-clock");
+               document.getElementById("whiteclock").classList.remove("running-clock");
+               document.getElementById("blackclock").classList.add("running-clock");
        } else {
-               $("#whiteclock").removeClass("running-clock");
-               $("#blackclock").removeClass("running-clock");
+               document.getElementById("whiteclock").classList.remove("running-clock");
+               document.getElementById("blackclock").classList.remove("running-clock");
        }
-       var remaining_ms;
+       let remaining_ms;
        if (color) {
-               var now = new Date().getTime() + client_clock_offset_ms;
+               let now = new Date().getTime() + client_clock_offset_ms;
                remaining_ms = data['position'][color + '_clock_target'] * 1000 - now;
                if (color === "white") {
                        white_clock_ms = remaining_ms;
@@ -1490,18 +1620,18 @@ var update_clock = function() {
        }
 
        if (white_clock_ms === null || black_clock_ms === null) {
-               $("#whiteclock").empty();
-               $("#blackclock").empty();
+               document.getElementById("whiteclock").replaceChildren();
+               document.getElementById("blackclock").replaceChildren();
                return;
        }
 
        // If either player has twenty minutes or less left, add the second counters.
        // This matches what DGT clocks do.
-       var show_seconds = (white_clock_ms < 60 * 20 * 1000 || black_clock_ms < 60 * 20 * 1000);
+       let show_seconds = (white_clock_ms < 60 * 20 * 1000 || black_clock_ms < 60 * 20 * 1000);
 
-       if (color) {
+       if (color && remaining_ms > 0) {
                // See when the clock will change next, and update right after that.
-               var next_update_ms;
+               let next_update_ms;
                if (show_seconds) {
                        next_update_ms = remaining_ms % 1000 + 100;
                } else {
@@ -1510,15 +1640,15 @@ var update_clock = function() {
                clock_timer = setTimeout(update_clock, next_update_ms);
        }
 
-       $("#whiteclock").text(format_clock(white_clock_ms, show_seconds));
-       $("#blackclock").text(format_clock(black_clock_ms, show_seconds));
+       document.getElementById("whiteclock").textContent = format_clock(white_clock_ms, show_seconds);
+       document.getElementById("blackclock").textContent = format_clock(black_clock_ms, show_seconds);
 }
 
 /**
- * @param {Number} remaining_ms
+ * @param {number} remaining_ms
  * @param {boolean} show_seconds
  */
-var format_clock = function(remaining_ms, show_seconds) {
+function format_clock(remaining_ms, show_seconds) {
        if (remaining_ms <= 0) {
                if (show_seconds) {
                        return "00:00:00";
@@ -1527,12 +1657,12 @@ var format_clock = function(remaining_ms, show_seconds) {
                }
        }
 
-       var remaining = Math.floor(remaining_ms / 1000);
-       var seconds = remaining % 60;
+       let remaining = Math.floor(remaining_ms / 1000);
+       let seconds = remaining % 60;
        remaining = (remaining - seconds) / 60;
-       var minutes = remaining % 60;
+       let minutes = remaining % 60;
        remaining = (remaining - minutes) / 60;
-       var hours = remaining;
+       let hours = remaining;
        if (show_seconds) {
                return format_2d(hours) + ":" + format_2d(minutes) + ":" + format_2d(seconds);
        } else {
@@ -1541,9 +1671,9 @@ var format_clock = function(remaining_ms, show_seconds) {
 }
 
 /**
- * @param {Number} x
+ * @param {number} x
  */
-var format_2d = function(x) {
+function format_2d(x) {
        if (x >= 10) {
                return x;
        } else {
@@ -1553,11 +1683,11 @@ var format_2d = function(x) {
 
 /**
  * @param {string} move
- * @param {Number} move_num Move number of this move.
+ * @param {number} move_num Move number of this move.
  * @param {boolean} white_to_play Whether white is to play this move.
  */
-var format_move_with_number = function(move, move_num, white_to_play) {
-       var ret;
+function format_move_with_number(move, move_num, white_to_play) {
+       let ret;
        if (white_to_play) {
                ret = move_num + '. ';
        } else {
@@ -1569,10 +1699,10 @@ var format_move_with_number = function(move, move_num, white_to_play) {
 
 /**
  * @param {string} move
- * @param {Number} halfmove_num Half-move number that is to be played,
+ * @param {number} halfmove_num Half-move number that is to be played,
  *   starting from 0.
  */
-var format_halfmove_with_number = function(move, halfmove_num) {
+function format_halfmove_with_number(move, halfmove_num) {
        return format_move_with_number(
                move,
                Math.floor(halfmove_num / 2) + 1,
@@ -1581,15 +1711,15 @@ var format_halfmove_with_number = function(move, halfmove_num) {
 
 /**
  * @param {Object} data
- * @param {Number} halfmove_num
+ * @param {number} halfmove_num
  */
-var format_tooltip = function(data, halfmove_num) {
+function format_tooltip(data, halfmove_num) {
        if (data['score_history'][halfmove_num + 1] ||
            (halfmove_num + 1) === data['position']['history'].length) {
                // Position is in the history, or it is the current position
                // (which is implicitly tacked onto the history).
-               var move;
-               var short_score;
+               let move;
+               let short_score;
                if ((halfmove_num + 1) === data['position']['history'].length) {
                        move = data['position']['last_move'];
                        short_score = format_short_score(data['score']);
@@ -1600,13 +1730,13 @@ var format_tooltip = function(data, halfmove_num) {
                if (halfmove_num === -1) {
                        return "Start position: " + short_score;
                } else {
-                       var move_with_number = format_halfmove_with_number(move, halfmove_num);
+                       let move_with_number = format_halfmove_with_number(move, halfmove_num);
                        return "After " + move_with_number + ": " + short_score;
                }
        } else {
-               for (var i = halfmove_num; i --> -1; ) {
+               for (let i = halfmove_num; i --> -1; ) {
                        if (data['score_history'][i]) {
-                               var move = data['position']['history'][i];
+                               let move = data['position']['history'][i];
                                if (i === -1) {
                                        return "[Analysis kept from start position]";
                                } else {
@@ -1617,20 +1747,11 @@ var format_tooltip = function(data, halfmove_num) {
        }
 }
 
-/**
- * @param {boolean} truncate_history
- */
-var set_truncate_history = function(truncate_history) {
-       truncate_display_history = truncate_history;
-       update_refutation_lines();
-}
-window['set_truncate_history'] = set_truncate_history;
-
 /**
  * @param {number} line_num
  * @param {number} move_num
  */
-var show_line = function(line_num, move_num) {
+function show_line(line_num, move_num) {
        if (line_num == -1) {
                current_display_line = null;
                current_display_move = null;
@@ -1643,8 +1764,8 @@ var show_line = function(line_num, move_num) {
                update_board();
                return;
        } else {
-               current_display_line = jQuery.extend({}, display_lines[line_num]);  // Shallow clone.
-               current_display_move = move_num + current_display_line.start_display_move_num;
+               current_display_line = {...display_lines[line_num]};  // Shallow clone.
+               current_display_move = move_num;
        }
        current_display_line_is_history = (line_num == 0);
 
@@ -1656,7 +1777,7 @@ var show_line = function(line_num, move_num) {
 }
 window['show_line'] = show_line;
 
-var prev_move = function() {
+function prev_move() {
        if (current_display_line &&
            current_display_move >= current_display_line.start_display_move_num) {
                --current_display_move;
@@ -1667,7 +1788,7 @@ var prev_move = function() {
 }
 window['prev_move'] = prev_move;
 
-var next_move = function() {
+function next_move() {
        if (current_display_line &&
            current_display_move < current_display_line.pv.length - 1) {
                ++current_display_move;
@@ -1678,16 +1799,16 @@ var next_move = function() {
 }
 window['next_move'] = next_move;
 
-var next_game = function() {
+function next_game() {
        if (current_games === null) {
                return;
        }
 
        // Try to find the game we are currently looking at.
-       for (var game_num = 0; game_num < current_games.length; ++game_num) {
-               var game = current_games[game_num];
+       for (let game_num = 0; game_num < current_games.length; ++game_num) {
+               let game = current_games[game_num];
                if (game['url'] === backend_url) {
-                       var next_game_num = (game_num + 1) % current_games.length;
+                       let next_game_num = (game_num + 1) % current_games.length;
                        switch_backend(current_games[next_game_num]);
                        return;
                }
@@ -1696,7 +1817,7 @@ var next_game = function() {
        // Couldn't find it; give up.
 }
 
-var update_historic_analysis = function() {
+function update_historic_analysis() {
        if (!current_display_line_is_history) {
                return;
        }
@@ -1706,85 +1827,115 @@ var update_historic_analysis = function() {
        }
 
        // Fetch old analysis for this line if it exists.
-       var hiddenboard = chess_from(current_display_line.start_fen, current_display_line.pv, current_display_move);
-       var filename = "/history/move" + (current_display_move + 1) + "-" +
+       let hiddenboard = chess_from(current_display_line.start_fen, current_display_line.pv, current_display_move);
+       let filename = "/history/move" + (current_display_move + 1) + "-" +
                hiddenboard.fen().replace(/ /g, '_').replace(/\//g, '-') + ".json";
 
-       current_historic_xhr = $.ajax({
-               url: filename
-       }).done(function(data, textstatus, xhr) {
-               displayed_analysis_data = data;
+       let handle_err = () => {
+               displayed_analysis_data = {'failed': true};
                update_board();
-       }).fail(function(jqXHR, textStatus, errorThrown) {
-               if (textStatus === "abort") {
-                       // Aborted because we are switching backends. Don't do anything;
-                       // we will already have been cleared.
-               } else {
-                       displayed_analysis_data = {'failed': true};
+       };
+
+       current_historic_xhr = new AbortController();
+       const signal = current_analysis_xhr.signal;
+       fetch(filename, { signal })
+               .then((response) => response.json().then(data => ({ok: response.ok, json: data})))  // ick
+               .then((obj) => {
+                       if (!obj.ok) {
+                               handle_err();
+                               return;
+                       }
+                       displayed_analysis_data = obj.json;
                        update_board();
-               }
-       });
+               })
+               .catch((err) => {
+                       if (err.name === 'AbortError') {
+                               // Aborted because we are switching backends. Abandon and don't retry,
+                               // because another one is already started for us.
+                       } else {
+                               console.log(err);
+                               handle_err();
+                       }
+               });
 }
 
 /**
  * @param {string} fen
  */
-var update_imbalance = function(fen) {
-       var hiddenboard = new Chess(fen);
-       var imbalance = {'k': 0, 'q': 0, 'r': 0, 'b': 0, 'n': 0, 'p': 0};
-       for (var row = 0; row < 8; ++row) {
-               for (var col = 0; col < 8; ++col) {
-                       var col_text = String.fromCharCode('a1'.charCodeAt(0) + col);
-                       var row_text = String.fromCharCode('a1'.charCodeAt(1) + row);
-                       var square = col_text + row_text;
-                       var contents = hiddenboard.get(square);
-                       if (contents !== null) {
-                               if (contents.color === 'w') {
-                                       ++imbalance[contents.type];
-                               } else {
-                                       --imbalance[contents.type];
-                               }
-                       }
-               }
-       }
-       var white_imbalance = '';
-       var black_imbalance = '';
-       for (var piece in imbalance) {
-               for (var i = 0; i < imbalance[piece]; ++i) {
-                       white_imbalance += '<img src="img/chesspieces/wikipedia/w' + piece.toUpperCase() + '.png" alt="" style="width: 15px;height: 15px;">';
-               }
-               for (var i = 0; i < -imbalance[piece]; ++i) {
-                       black_imbalance += '<img src="img/chesspieces/wikipedia/b' + piece.toUpperCase() + '.png" alt="" style="width: 15px;height: 15px;">';
+function update_imbalance(fen) {
+       let imbalance = {'k': 0, 'q': 0, 'r': 0, 'b': 0, 'n': 0, 'p': 0};
+       for (const c of fen) {
+               if (c === ' ') {
+                       // End of board
+                       break;
+               }
+               if (c != c.toUpperCase()) {
+                       --imbalance[c];
+               } else if (c != c.toLowerCase()) {
+                       ++imbalance[c.toLowerCase()];
+               }
+       }
+
+       let white_imbalance = document.getElementById('whiteimbalance');
+       let black_imbalance = document.getElementById('blackimbalance');
+       white_imbalance.textContent = '';
+       black_imbalance.textContent = '';
+       for (let piece in imbalance) {
+               for (let i = 0; i < imbalance[piece]; ++i) {
+                       let i1 = document.createElement('img');
+                       i1.src = svg_pieces['w' + piece.toUpperCase()];
+                       i1.setAttribute('alt', piece.toUpperCase());
+                       i1.classList.add('imbalance-piece');
+                       white_imbalance.appendChild(i1);
+
+                       let i2 = document.createElement('img');
+                       i2.src = svg_pieces['b' + piece.toUpperCase()];
+                       i2.setAttribute('alt', piece.toUpperCase());
+                       i2.classList.add('imbalance-inverted-piece');
+                       white_imbalance.appendChild(i2);
+               }
+               for (let i = 0; i < -imbalance[piece]; ++i) {
+                       let i1 = document.createElement('img');
+                       i1.src = svg_pieces['b' + piece.toUpperCase()];
+                       i1.setAttribute('alt', piece.toUpperCase());
+                       i1.classList.add('imbalance-piece');
+                       black_imbalance.appendChild(i1);
+
+                       let i2 = document.createElement('img');
+                       i2.src = svg_pieces['w' + piece.toUpperCase()];
+                       i2.setAttribute('alt', piece.toUpperCase());
+                       i2.classList.add('imbalance-inverted-piece');
+                       black_imbalance.appendChild(i2);
                }
        }
-       $('#whiteimbalance').html(white_imbalance);
-       $('#blackimbalance').html(black_imbalance);
 }
 
 /** Mark the currently selected move in red.
  * Also replaces the PV with the current displayed line if it's not shown
  * anywhere else on the screen.
  */
-var update_move_highlight = function() {
+function update_move_highlight() {
        if (highlighted_move !== null) {
-               highlighted_move.removeClass('highlight'); 
+               highlighted_move.classList.remove('highlight'); 
        }
        if (current_display_line) {
-               var display_line_num = find_display_line_matching_num();
+               let display_line_num = find_display_line_matching_num();
                if (display_line_num === null) {
                        // Replace the PV with the (complete) line.
-                       $("#pvtitle").text("Exploring:");
+                       document.getElementById("pvtitle").textContent = "Exploring:";
                        current_display_line.start_display_move_num = 0;
                        display_lines.push(current_display_line);
-                       $("#pv").html(print_pv(display_lines.length - 1, null));  // FIXME
+                       document.getElementById("pv").replaceChildren(print_pv(display_lines.length - 1, null));  // FIXME
                        display_line_num = display_lines.length - 1;
 
                        // Clear out the PV, so it's not selected by anything later.
                        display_lines[1].pv = [];
                }
 
-               highlighted_move = $("#automove" + display_line_num + "-" + (current_display_move - current_display_line.start_display_move_num));
-               highlighted_move.addClass('highlight');
+               highlighted_move = document.getElementById("automove" + display_line_num + "-" + current_display_move);
+               if (highlighted_move !== null) {
+                       highlighted_move.classList.add('highlight');
+               }
        }
 }
 
@@ -1795,14 +1946,14 @@ var update_move_highlight = function() {
  *
  * @return {?number}
  */
-var find_display_line_matching_num = function() {
-       for (var i = 0; i < display_lines.length; ++i) {
-               var line = display_lines[i];
+function find_display_line_matching_num() {
+       for (let i = 0; i < display_lines.length; ++i) {
+               let line = display_lines[i];
                if (line.start_display_move_num > 0) continue;
                if (current_display_line.start_fen !== line.start_fen) continue;
                if (current_display_line.pv.length !== line.pv.length) continue;
-               var ok = true;
-               for (var j = 0; j < line.pv.length; ++j) {
+               let ok = true;
+               for (let j = 0; j < line.pv.length; ++j) {
                        if (current_display_line.pv[j] !== line.pv[j]) {
                                ok = false;
                                break;
@@ -1820,31 +1971,31 @@ var find_display_line_matching_num = function() {
  * TODO: This should really be called only whenever something changes,
  * instead of all the time.
  */
-var update_displayed_line = function() {
+function update_displayed_line() {
        if (current_display_line === null) {
-               $("#linenav").hide();
-               $("#linemsg").show();
+               document.getElementById("linenav").style.display = 'none';
+               document.getElementById("linemsg").style.display = 'revert';
                display_fen = base_fen;
                set_board_position(base_fen);
                update_imbalance(base_fen);
                return;
        }
 
-       $("#linenav").show();
-       $("#linemsg").hide();
+       document.getElementById("linenav").style.display = 'revert';
+       document.getElementById("linemsg").style.display = 'none';
 
        if (current_display_move <= 0) {
-               $("#prevmove").html("Previous");
+               document.getElementById("prevmove").textContent = "Previous";
        } else {
-               $("#prevmove").html("<a href=\"javascript:prev_move();\">Previous</a></span>");
+               document.getElementById("prevmove").innerHTML = "<a href=\"javascript:prev_move();\">Previous</a></span>";
        }
        if (current_display_move == current_display_line.pv.length - 1) {
-               $("#nextmove").html("Next");
+               document.getElementById("nextmove").textContent = "Next";
        } else {
-               $("#nextmove").html("<a href=\"javascript:next_move();\">Next</a></span>");
+               document.getElementById("nextmove").innerHTML = "<a href=\"javascript:next_move();\">Next</a></span>";
        }
 
-       var hiddenboard = chess_from(current_display_line.start_fen, current_display_line.pv, current_display_move);
+       let hiddenboard = chess_from(current_display_line.start_fen, current_display_line.pv, current_display_move);
        set_board_position(hiddenboard.fen());
        if (display_fen !== hiddenboard.fen() && !current_display_line_is_history) {
                // Fire off a hash request, since we're now off the main position
@@ -1855,10 +2006,11 @@ var update_displayed_line = function() {
        update_imbalance(hiddenboard.fen());
 }
 
-var set_board_position = function(new_fen) {
+function set_board_position(new_fen) {
        board_is_animating = true;
-       var old_fen = board.fen();
-       board.position(new_fen);
+       let old_fen = board.fen();
+       let animate = old_fen !== '8/8/8/8/8/8/8/';
+       board.position(new_fen, animate);
        if (board.fen() === old_fen) {
                board_is_animating = false;
        }
@@ -1867,25 +2019,25 @@ var set_board_position = function(new_fen) {
 /**
  * @param {boolean} param_enable_sound
  */
-var set_sound = function(param_enable_sound) {
+function set_sound(param_enable_sound) {
        enable_sound = param_enable_sound;
        if (enable_sound) {
-               $("#soundon").html("<strong>On</strong>");
-               $("#soundoff").html("<a href=\"javascript:set_sound(false)\">Off</a>");
+               document.getElementById("soundon").innerHTML = "<strong>On</strong>";
+               document.getElementById("soundoff").innerHTML = "<a href=\"javascript:set_sound(false)\">Off</a>";
 
                // Seemingly at least Firefox prefers MP3 over Opus; tell it otherwise,
                // and also preload the file since the user has selected audio.
-               var ding = document.getElementById('ding');
+               let ding = document.getElementById('ding');
                if (ding && ding.canPlayType && ding.canPlayType('audio/ogg; codecs="opus"') === 'probably') {
                        ding.src = 'ding.opus';
                        ding.load();
                }
        } else {
-               $("#soundon").html("<a href=\"javascript:set_sound(true)\">On</a>");
-               $("#soundoff").html("<strong>Off</strong>");
+               document.getElementById("soundon").innerHTML = "<a href=\"javascript:set_sound(true)\">On</a>";
+               document.getElementById("soundoff").innerHTML = "<strong>Off</strong>";
        }
        if (supports_html5_storage()) {
-               localStorage['enable_sound'] = enable_sound ? 1 : 0;
+               window['localStorage']['enable_sound'] = enable_sound ? 1 : 0;
        }
 }
 window['set_sound'] = set_sound;
@@ -1893,7 +2045,7 @@ window['set_sound'] = set_sound;
 /** Send off a hash probe request to the backend.
  * @param {string} fen
  */
-var explore_hash = function(fen) {
+function explore_hash(fen) {
        // If we already have a backend response going, abort it.
        if (current_hash_xhr) {
                current_hash_xhr.abort();
@@ -1902,19 +2054,25 @@ var explore_hash = function(fen) {
                clearTimeout(current_hash_display_timer);
                current_hash_display_timer = null;
        }
-       $("#refutationlines").empty();
-       current_hash_xhr = $.ajax({
-               url: backend_hash_url + "?fen=" + fen
-       }).done(function(data, textstatus, xhr) {
-               show_explore_hash_results(data, fen);
-       });
+       document.getElementById("refutationlines").replaceChildren();
+
+       current_hash_xhr = new AbortController();
+       const signal = current_analysis_xhr.signal;
+       fetch(backend_hash_url + "?fen=" + fen, { signal })
+               .then((response) => response.json())
+               .then((data) => { show_explore_hash_results(data, fen); })
+               .catch((err) => {
+                       // Truncate the lines, since we already cleared the display.
+                       display_lines = [ display_lines[0], display_lines[1] ];
+                       update_move_highlight();
+               });
 }
 
 /** Process the JSON response from a hash probe request.
  * @param {!Object} data
  * @param {string} fen
  */
-var show_explore_hash_results = function(data, fen) {
+function show_explore_hash_results(data, fen) {
        if (board_is_animating) {
                // Updating while the animation is still going causes
                // the animation to jerk. This is pretty crude, but it will do.
@@ -1923,12 +2081,13 @@ var show_explore_hash_results = function(data, fen) {
        }
        current_hash_display_timer = null;
        hash_refutation_lines = data['lines'];
+       hash_refutation_lines_base_fen = fen;
        update_board();
 }
 
 // almost all of this stuff comes from the chessboard.js example page
-var onDragStart = function(source, piece, position, orientation) {
-       var pseudogame = new Chess(display_fen);
+function onDragStart(source, piece, position, orientation) {
+       let pseudogame = new Chess(display_fen);
        if (pseudogame.game_over() === true ||
            (pseudogame.turn() === 'w' && piece.search(/^b/) !== -1) ||
            (pseudogame.turn() === 'b' && piece.search(/^w/) !== -1)) {
@@ -1937,53 +2096,62 @@ var onDragStart = function(source, piece, position, orientation) {
 
        recommended_move = get_best_move(pseudogame, source, null, pseudogame.turn() === 'b');
        if (recommended_move) {
-               var squareEl = $('#board .square-' + recommended_move.to);
-               squareEl.addClass('highlight1-32417');
+               let squareEl = document.querySelector('#board .square-' + recommended_move.to);
+               squareEl.classList.add('highlight1-32417');
        }
        return true;
 }
 
-var mousedownSquare = function(e) {
+function mousedownSquare(e) {
+       if (!e.target || !e.target.getAttribute('data-square')) {
+               return;
+       }
+
        reverse_dragging_from = null;
-       var square = $(this).attr('data-square');
+       let square = e.target.getAttribute('data-square');
 
-       var pseudogame = new Chess(display_fen);
+       let pseudogame = new Chess(display_fen);
        if (pseudogame.game_over() === true) {
                return;
        }
 
        // If the square is empty, or has a piece of the side not to move,
        // we handle it. If not, normal piece dragging will take it.
-       var position = board.position();
+       let position = board.position();
        if (!position.hasOwnProperty(square) ||
            (pseudogame.turn() === 'w' && position[square].search(/^b/) !== -1) ||
            (pseudogame.turn() === 'b' && position[square].search(/^w/) !== -1)) {
                reverse_dragging_from = square;
                recommended_move = get_best_move(pseudogame, null, square, pseudogame.turn() === 'b');
                if (recommended_move) {
-                       var squareEl = $('#board .square-' + recommended_move.from);
-                       squareEl.addClass('highlight1-32417');
-                       squareEl = $('#board .square-' + recommended_move.to);
-                       squareEl.addClass('highlight1-32417');
+                       let squareEl = document.querySelector('#board .square-' + recommended_move.from);
+                       squareEl.classList.add('highlight1-32417');
+                       squareEl = document.querySelector('#board .square-' + recommended_move.to);
+                       squareEl.classList.add('highlight1-32417');
                }
        }
 }
 
-var mouseupSquare = function(e) {
+function mouseupSquare(e) {
+       if (!e.target || !e.target.getAttribute('data-square')) {
+               return;
+       }
        if (reverse_dragging_from === null) {
                return;
        }
-       var source = $(this).attr('data-square');
-       var target = reverse_dragging_from;
+       let source = e.target.getAttribute('data-square');
+       let target = reverse_dragging_from;
        reverse_dragging_from = null;
        if (onDrop(source, target) !== 'snapback') {
                onSnapEnd(source, target);
        }
-       $("#board").find('.square-55d63').removeClass('highlight1-32417');
+       document.getElementById("board").querySelectorAll('.square-55d63.highlight1-32417').forEach((square) => {
+               square.classList.remove('highlight1-32417');
+       });
 }
 
-var get_best_move = function(game, source, target, invert) {
-       var moves = game.moves({ verbose: true });
+function get_best_move(game, source, target, invert) {
+       let moves = game.moves({ verbose: true });
        if (source !== null) {
                moves = moves.filter(function(move) { return move.from == source; });
        }
@@ -1999,40 +2167,41 @@ var get_best_move = function(game, source, target, invert) {
 
        // More than one move. Use the display lines (if we have them)
        // to disambiguate; otherwise, we have no information.
-       var move_hash = {};
-       for (var i = 0; i < moves.length; ++i) {
+       let move_hash = {};
+       for (let i = 0; i < moves.length; ++i) {
                move_hash[moves[i].san] = moves[i];
        }
 
        // See if we're already exploring some line.
        if (current_display_line &&
            current_display_move < current_display_line.pv.length - 1) {
-               var first_move = current_display_line.pv[current_display_move + 1];
+               let first_move = current_display_line.pv[current_display_move + 1];
                if (move_hash[first_move]) {
                        return move_hash[first_move];
                }
        }
 
        // History and PV take priority over the display lines.
-       for (var i = 0; i < 2; ++i) {
-               var line = display_lines[i];
-               var first_move = line.pv[line.start_display_move_num];
+       for (let i = 0; i < 2; ++i) {
+               let line = display_lines[i];
+               let first_move = line.pv[line.start_display_move_num];
                if (move_hash[first_move]) {
                        return move_hash[first_move];
                }
        }
 
-       var best_move = null;
-       var best_move_score = null;
+       let best_move = null;
+       let best_move_score = null;
 
-       for (var move in refutation_lines) {
-               var line = refutation_lines[move];
+       let refutation_lines = choose_displayed_refutation_lines()[0];
+       for (let move in refutation_lines) {
+               let line = refutation_lines[move];
                if (!line['score']) {
                        continue;
                }
-               var first_move = line['pv'][0];
+               let first_move = line['pv'][0];
                if (move_hash[first_move]) {
-                       var score = compute_score_sort_key(line['score'], line['depth'], invert);
+                       let score = compute_score_sort_key(line['score'], line['depth'], invert);
                        if (best_move_score === null || score > best_move_score) {
                                best_move = move_hash[first_move];
                                best_move_score = score;
@@ -2042,7 +2211,7 @@ var get_best_move = function(game, source, target, invert) {
        return best_move;
 }
 
-var onDrop = function(source, target) {
+function onDrop(source, target) {
        if (source === target) {
                if (recommended_move === null) {
                        return 'snapback';
@@ -2056,8 +2225,8 @@ var onDrop = function(source, target) {
        }
 
        // see if the move is legal
-       var pseudogame = new Chess(display_fen);
-       var move = pseudogame.move({
+       let pseudogame = new Chess(display_fen);
+       let move = pseudogame.move({
                from: source,
                to: target,
                promotion: 'q' // NOTE: always promote to a queen for example simplicity
@@ -2067,19 +2236,71 @@ var onDrop = function(source, target) {
        if (move === null) return 'snapback';
 }
 
-var onSnapEnd = function(source, target) {
+/**
+ * If we are in admin mode, send this move to the backend.
+ *
+ * @param {string} fen
+ * @param {string} move
+ */
+function send_chosen_move(fen, move) {
+       if (admin_password !== null) {
+               let history = current_analysis_data['position']['history'];
+               let url = '/manual-override.pl';
+               url += '?fen=' + encodeURIComponent(fen);
+               url += '&history=' + encodeURIComponent(JSON.stringify(history));
+               url += '&move=' + encodeURIComponent(move);
+               url += '&player_w=' + encodeURIComponent(current_analysis_data['position']['player_w']);
+               url += '&player_b=' + encodeURIComponent(current_analysis_data['position']['player_b']);
+               url += '&password=' + encodeURIComponent(admin_password);
+
+               console.log(fen, history);
+               fetch(url);  // Ignore the result.
+       }
+}
+
+function undo_move() {
+       if (admin_password !== null) {
+               let history = current_analysis_data['position']['history'];
+               history = history.slice(0, history.length - 1);
+
+               let position = current_analysis_data['position']['start_fen'];
+               let hiddenboard = chess_from(position, history, history.length);
+               let fen = hiddenboard.fen();
+
+               let url = '/manual-override.pl';
+               url += '?fen=' + encodeURIComponent(fen);
+               url += '&history=' + encodeURIComponent(JSON.stringify(history));
+               url += '&move=null';
+               url += '&player_w=' + encodeURIComponent(current_analysis_data['position']['player_w']);
+               url += '&player_b=' + encodeURIComponent(current_analysis_data['position']['player_b']);
+               url += '&password=' + encodeURIComponent(admin_password);
+
+               console.log(fen, history);
+               fetch(url);  // Ignore the result.
+       }
+}
+window['undo_move'] = undo_move;
+
+function onSnapEnd(source, target) {
        if (source === target && recommended_move !== null) {
                source = recommended_move.from;
                target = recommended_move.to;
        }
        recommended_move = null;
-       var pseudogame = new Chess(display_fen);
-       var move = pseudogame.move({
+       let pseudogame = new Chess(display_fen);
+       let move = pseudogame.move({
                from: source,
                to: target,
                promotion: 'q' // NOTE: always promote to a queen for example simplicity
        });
 
+       if (admin_password !== null) {
+               send_chosen_move(display_fen, move.san);
+               return;
+       }
+
+       // Move ahead on the line we're on -- this includes history if we've
+       // gone backwards.
        if (current_display_line &&
            current_display_move < current_display_line.pv.length - 1 &&
            current_display_line.pv[current_display_move + 1] === move.san) {
@@ -2089,25 +2310,29 @@ var onSnapEnd = function(source, target) {
 
        // Walk down the displayed lines until we find one that starts with
        // this move, then select that. Note that this gives us a good priority
-       // order (history first, then PV, then multi-PV lines).
-       for (var i = 0; i < display_lines.length; ++i) {
+       // order (PV, then multi-PV lines; history was already dealt with above,
+       // as it's the only line that originates backwards).
+       for (let i = 1; i < display_lines.length; ++i) {
                if (i == 1 && current_display_line) {
                        // Do not choose PV if not on it.
                        continue;
                }
-               var line = display_lines[i];
+               let line = display_lines[i];
                if (line.pv[line.start_display_move_num] === move.san) {
-                       show_line(i, 0);
+                       show_line(i, line.start_display_move_num);
                        return;
                }
        }
 
        // Shouldn't really be here if we have hash probes, but there's really
        // nothing we can do.
+       // FIXME: Just make a new line, probably (even if we don't have hash moves).
+       // As it is, we can actually drag (but not click) such a move in the UI,
+       // but it has no effect on what we're probing.
 }
 // End of dragging-related code.
 
-var fmt_cp = function(v) {
+function fmt_cp(v) {
        if (v === 0) {
                return "0.00";
        } else if (v > 0) {
@@ -2118,22 +2343,22 @@ var fmt_cp = function(v) {
        }
 }
 
-var format_short_score = function(score) {
+function format_short_score(score) {
        if (!score) {
                return "???";
        }
        if (score[0] === 'T' || score[0] === 't') {
-               var ret = "TB\u00a0";
+               let ret = "TB\u00a0";
                if (score[2]) {  // Is a bound.
                        ret = score[2] + "\u00a0TB\u00a0";
                }
                if (score[0] === 'T') {
                        return ret + Math.ceil(score[1] / 2);
                } else {
-                       return ret + "-" + Math.ceil(-score[1] / 2);
+                       return ret + "-" + Math.ceil(score[1] / 2);
                }
        } else if (score[0] === 'M' || score[0] === 'm') {
-               var sign = (score[0] === 'm') ? '-' : '';
+               let sign = (score[0] === 'm') ? '-' : '';
                if (score[2]) {  // Is a bound.
                        return score[2] + "\u00a0M " + sign + score[1];
                } else {
@@ -2151,7 +2376,7 @@ var format_short_score = function(score) {
        return null;
 }
 
-var format_long_score = function(score) {
+function format_long_score(score) {
        if (!score) {
                return "???";
        }
@@ -2187,7 +2412,7 @@ var format_long_score = function(score) {
        return null;
 }
 
-var compute_plot_score = function(score) {
+function compute_plot_score(score) {
        if (score[0] === 'M' || score[0] === 'T') {
                return 500;
        } else if (score[0] === 'm' || score[0] === 't') {
@@ -2210,11 +2435,10 @@ var compute_plot_score = function(score) {
  * @param score The score digest tuple.
  * @param {?number} depth Depth the move has been computed to, or null.
  * @param {boolean} invert Whether black is to play.
- * @param {boolean=} depth_secondary_key
  * @return {number}
  */
-var compute_score_sort_key = function(score, depth, invert, depth_secondary_key) {
-       var s;
+function compute_score_sort_key(score, depth, invert) {
+       let s;
        if (!score) {
                return -10000000;
        }
@@ -2237,11 +2461,7 @@ var compute_score_sort_key = function(score, depth, invert, depth_secondary_key)
        }
        if (s) {
                if (invert) s = -s;
-               if (depth_secondary_key) {
-                       return s * 200 + (depth || 0);
-               } else {
-                       return s;
-               }
+               return s;
        } else {
                return null;
        }
@@ -2250,7 +2470,7 @@ var compute_score_sort_key = function(score, depth, invert, depth_secondary_key)
 /**
  * @param {Object} game
  */
-var switch_backend = function(game) {
+function switch_backend(game) {
        // Stop looking at historic data.
        current_display_line = null;
        current_display_move = null;
@@ -2289,43 +2509,79 @@ var switch_backend = function(game) {
 window['switch_backend'] = switch_backend;
 
 window['flip'] = function() { board.flip(); redraw_arrows(); };
+window['set_delay_ms'] = function(ms) { delay_ms = ms; console.log('Delay is now ' + ms + ' ms.'); };
+
+// Mostly from Wikipedia's chess set as of October 2022, but some pieces are from
+// the 2013 version, as I like those better (and it matches the 2014 PNGs; nobody
+// really likes change, do they?). That is wK, bK, bQ. wQ is also slightly different,
+// but not enough to notice.
+const svg_pieces = {
+       'wK': 'data:image/svg+xml,<?xml version=%221.0%22 encoding=%22UTF-8%22 standalone=%22no%22?>%0A<!DOCTYPE svg PUBLIC %22-//W3C//DTD SVG 1.1//EN%22 %22http://www.w3.org/Graphics/SVG/1.1/DTD/svg11.dtd%22>%0A<svg xmlns=%22http://www.w3.org/2000/svg%22 version=%221.1%22 width=%2245%22 height=%2245%22><g style=%22fill:none;fill-opacity:1;fill-rule:evenodd;stroke:%23000000;stroke-width:1.5;stroke-linecap:round;stroke-linejoin:round;stroke-miterlimit:4;stroke-dasharray:none;stroke-opacity:1%22><path d=%22M 22.5,11.63 L 22.5,6%22 style=%22fill:none;stroke:%23000000;stroke-linejoin:miter%22/><path d=%22M 20,8 L 25,8%22 style=%22fill:none;stroke:%23000000;stroke-linejoin:miter%22/><path d=%22M 22.5,25 C 22.5,25 27,17.5 25.5,14.5 C 25.5,14.5 24.5,12 22.5,12 C 20.5,12 19.5,14.5 19.5,14.5 C 18,17.5 22.5,25 22.5,25%22 style=%22fill:%23ffffff;stroke:%23000000;stroke-linecap:butt;stroke-linejoin:miter%22/><path d=%22M 11.5,37 C 17,40.5 27,40.5 32.5,37 L 32.5,30 C 32.5,30 41.5,25.5 38.5,19.5 C 34.5,13 25,16 22.5,23.5 L 22.5,27 L 22.5,23.5 C 19,16 9.5,13 6.5,19.5 C 3.5,25.5 11.5,29.5 11.5,29.5 L 11.5,37 z %22 style=%22fill:%23ffffff;stroke:%23000000%22/><path d=%22M 11.5,30 C 17,27 27,27 32.5,30%22 style=%22fill:none;stroke:%23000000%22/><path d=%22M 11.5,33.5 C 17,30.5 27,30.5 32.5,33.5%22 style=%22fill:none;stroke:%23000000%22/><path d=%22M 11.5,37 C 17,34 27,34 32.5,37%22 style=%22fill:none;stroke:%23000000%22/></g></svg>',
+       'wQ': 'data:image/svg+xml,<?xml version=%221.0%22 encoding=%22UTF-8%22 standalone=%22no%22?>%0A<!DOCTYPE svg PUBLIC %22-//W3C//DTD SVG 1.1//EN%22 %22http://www.w3.org/Graphics/SVG/1.1/DTD/svg11.dtd%22>%0A<svg xmlns=%22http://www.w3.org/2000/svg%22 version=%221.1%22 width=%2245%22 height=%2245%22><g style=%22fill:%23ffffff;stroke:%23000000;stroke-width:1.5;stroke-linejoin:round%22><path d=%22M 9,26 C 17.5,24.5 30,24.5 36,26 L 38.5,13.5 L 31,25 L 30.7,10.9 L 25.5,24.5 L 22.5,10 L 19.5,24.5 L 14.3,10.9 L 14,25 L 6.5,13.5 L 9,26 z%22/><path d=%22M 9,26 C 9,28 10.5,28 11.5,30 C 12.5,31.5 12.5,31 12,33.5 C 10.5,34.5 11,36 11,36 C 9.5,37.5 11,38.5 11,38.5 C 17.5,39.5 27.5,39.5 34,38.5 C 34,38.5 35.5,37.5 34,36 C 34,36 34.5,34.5 33,33.5 C 32.5,31 32.5,31.5 33.5,30 C 34.5,28 36,28 36,26 C 27.5,24.5 17.5,24.5 9,26 z%22/><path d=%22M 11.5,30 C 15,29 30,29 33.5,30%22 style=%22fill:none%22/><path d=%22M 12,33.5 C 18,32.5 27,32.5 33,33.5%22 style=%22fill:none%22/><circle cx=%226%22 cy=%2212%22 r=%222%22/><circle cx=%2214%22 cy=%229%22 r=%222%22/><circle cx=%2222.5%22 cy=%228%22 r=%222%22/><circle cx=%2231%22 cy=%229%22 r=%222%22/><circle cx=%2239%22 cy=%2212%22 r=%222%22/></g></svg>',
+       'wR': 'data:image/svg+xml,<?xml version=%221.0%22 encoding=%22UTF-8%22 standalone=%22no%22?>%0A<!DOCTYPE svg PUBLIC %22-//W3C//DTD SVG 1.1//EN%22 %22http://www.w3.org/Graphics/SVG/1.1/DTD/svg11.dtd%22>%0A<svg xmlns=%22http://www.w3.org/2000/svg%22 version=%221.1%22 width=%2245%22 height=%2245%22><g style=%22opacity:1;fill:%23ffffff;fill-opacity:1;fill-rule:evenodd;stroke:%23000000;stroke-width:1.5;stroke-linecap:round;stroke-linejoin:round;stroke-miterlimit:4;stroke-dasharray:none;stroke-opacity:1%22 transform=%22translate(0,0.3)%22><path d=%22M 9,39 L 36,39 L 36,36 L 9,36 L 9,39 z %22 style=%22stroke-linecap:butt%22/><path d=%22M 12,36 L 12,32 L 33,32 L 33,36 L 12,36 z %22 style=%22stroke-linecap:butt%22/><path d=%22M 11,14 L 11,9 L 15,9 L 15,11 L 20,11 L 20,9 L 25,9 L 25,11 L 30,11 L 30,9 L 34,9 L 34,14%22 style=%22stroke-linecap:butt%22/><path d=%22M 34,14 L 31,17 L 14,17 L 11,14%22/><path d=%22M 31,17 L 31,29.5 L 14,29.5 L 14,17%22 style=%22stroke-linecap:butt;stroke-linejoin:miter%22/><path d=%22M 31,29.5 L 32.5,32 L 12.5,32 L 14,29.5%22/><path d=%22M 11,14 L 34,14%22 style=%22fill:none;stroke:%23000000;stroke-linejoin:miter%22/></g></svg>',
+       'wB': 'data:image/svg+xml,<?xml version=%221.0%22 encoding=%22UTF-8%22 standalone=%22no%22?>%0A<!DOCTYPE svg PUBLIC %22-//W3C//DTD SVG 1.1//EN%22 %22http://www.w3.org/Graphics/SVG/1.1/DTD/svg11.dtd%22>%0A<svg xmlns=%22http://www.w3.org/2000/svg%22 version=%221.1%22 width=%2245%22 height=%2245%22><g style=%22opacity:1;fill:none;fill-rule:evenodd;fill-opacity:1;stroke:%23000000;stroke-width:1.5;stroke-linecap:round;stroke-linejoin:round;stroke-miterlimit:4;stroke-dasharray:none;stroke-opacity:1%22 transform=%22translate(0,0.6)%22><g style=%22fill:%23ffffff;stroke:%23000000;stroke-linecap:butt%22><path d=%22M 9,36 C 12.39,35.03 19.11,36.43 22.5,34 C 25.89,36.43 32.61,35.03 36,36 C 36,36 37.65,36.54 39,38 C 38.32,38.97 37.35,38.99 36,38.5 C 32.61,37.53 25.89,38.96 22.5,37.5 C 19.11,38.96 12.39,37.53 9,38.5 C 7.65,38.99 6.68,38.97 6,38 C 7.35,36.54 9,36 9,36 z%22/><path d=%22M 15,32 C 17.5,34.5 27.5,34.5 30,32 C 30.5,30.5 30,30 30,30 C 30,27.5 27.5,26 27.5,26 C 33,24.5 33.5,14.5 22.5,10.5 C 11.5,14.5 12,24.5 17.5,26 C 17.5,26 15,27.5 15,30 C 15,30 14.5,30.5 15,32 z%22/><path d=%22M 25 8 A 2.5 2.5 0 1 1 20,8 A 2.5 2.5 0 1 1 25 8 z%22/></g><path d=%22M 17.5,26 L 27.5,26 M 15,30 L 30,30 M 22.5,15.5 L 22.5,20.5 M 20,18 L 25,18%22 style=%22fill:none;stroke:%23000000;stroke-linejoin:miter%22/></g></svg>',
+       'wN': 'data:image/svg+xml,<?xml version=%221.0%22 encoding=%22UTF-8%22 standalone=%22no%22?>%0A<!DOCTYPE svg PUBLIC %22-//W3C//DTD SVG 1.1//EN%22 %22http://www.w3.org/Graphics/SVG/1.1/DTD/svg11.dtd%22>%0A<svg xmlns=%22http://www.w3.org/2000/svg%22 version=%221.1%22 width=%2245%22 height=%2245%22><g style=%22opacity:1;fill:none;fill-opacity:1;fill-rule:evenodd;stroke:%23000000;stroke-width:1.5;stroke-linecap:round;stroke-linejoin:round;stroke-miterlimit:4;stroke-dasharray:none;stroke-opacity:1%22 transform=%22translate(0,0.3)%22><path d=%22M 22,10 C 32.5,11 38.5,18 38,39 L 15,39 C 15,30 25,32.5 23,18%22 style=%22fill:%23ffffff;stroke:%23000000%22/><path d=%22M 24,18 C 24.38,20.91 18.45,25.37 16,27 C 13,29 13.18,31.34 11,31 C 9.958,30.06 12.41,27.96 11,28 C 10,28 11.19,29.23 10,30 C 9,30 5.997,31 6,26 C 6,24 12,14 12,14 C 12,14 13.89,12.1 14,10.5 C 13.27,9.506 13.5,8.5 13.5,7.5 C 14.5,6.5 16.5,10 16.5,10 L 18.5,10 C 18.5,10 19.28,8.008 21,7 C 22,7 22,10 22,10%22 style=%22fill:%23ffffff;stroke:%23000000%22/><path d=%22M 9.5 25.5 A 0.5 0.5 0 1 1 8.5,25.5 A 0.5 0.5 0 1 1 9.5 25.5 z%22 style=%22fill:%23000000;stroke:%23000000%22/><path d=%22M 15 15.5 A 0.5 1.5 0 1 1 14,15.5 A 0.5 1.5 0 1 1 15 15.5 z%22 transform=%22matrix(0.866,0.5,-0.5,0.866,9.693,-5.173)%22 style=%22fill:%23000000;stroke:%23000000%22/></g></svg>',
+       'wP': 'data:image/svg+xml,<?xml version=%221.0%22 encoding=%22UTF-8%22 standalone=%22no%22?>%0A<!DOCTYPE svg PUBLIC %22-//W3C//DTD SVG 1.1//EN%22 %22http://www.w3.org/Graphics/SVG/1.1/DTD/svg11.dtd%22>%0A<svg xmlns=%22http://www.w3.org/2000/svg%22 version=%221.1%22 width=%2245%22 height=%2245%22><path d=%22m 22.5,9 c -2.21,0 -4,1.79 -4,4 0,0.89 0.29,1.71 0.78,2.38 C 17.33,16.5 16,18.59 16,21 c 0,2.03 0.94,3.84 2.41,5.03 C 15.41,27.09 11,31.58 11,39.5 H 34 C 34,31.58 29.59,27.09 26.59,26.03 28.06,24.84 29,23.03 29,21 29,18.59 27.67,16.5 25.72,15.38 26.21,14.71 26.5,13.89 26.5,13 c 0,-2.21 -1.79,-4 -4,-4 z%22 style=%22opacity:1;fill:%23ffffff;fill-opacity:1;fill-rule:nonzero;stroke:%23000000;stroke-width:1.5;stroke-linecap:round;stroke-linejoin:miter;stroke-miterlimit:4;stroke-dasharray:none;stroke-opacity:1%22/></svg>',
+       'bK': 'data:image/svg+xml,<?xml version=%221.0%22 encoding=%22UTF-8%22 standalone=%22no%22?>%0A<!DOCTYPE svg PUBLIC %22-//W3C//DTD SVG 1.1//EN%22 %22http://www.w3.org/Graphics/SVG/1.1/DTD/svg11.dtd%22>%0A<svg xmlns=%22http://www.w3.org/2000/svg%22 version=%221.1%22 width=%2245%22 height=%2245%22><g style=%22fill:none;fill-opacity:1;fill-rule:evenodd;stroke:%23000000;stroke-width:1.5;stroke-linecap:round;stroke-linejoin:round;stroke-miterlimit:4;stroke-dasharray:none;stroke-opacity:1%22><path d=%22M 22.5,11.63 L 22.5,6%22 style=%22fill:none;stroke:%23000000;stroke-linejoin:miter%22 id=%22path6570%22/><path d=%22M 22.5,25 C 22.5,25 27,17.5 25.5,14.5 C 25.5,14.5 24.5,12 22.5,12 C 20.5,12 19.5,14.5 19.5,14.5 C 18,17.5 22.5,25 22.5,25%22 style=%22fill:%23000000;fill-opacity:1;stroke-linecap:butt;stroke-linejoin:miter%22/><path d=%22M 11.5,37 C 17,40.5 27,40.5 32.5,37 L 32.5,30 C 32.5,30 41.5,25.5 38.5,19.5 C 34.5,13 25,16 22.5,23.5 L 22.5,27 L 22.5,23.5 C 19,16 9.5,13 6.5,19.5 C 3.5,25.5 11.5,29.5 11.5,29.5 L 11.5,37 z %22 style=%22fill:%23000000;stroke:%23000000%22/><path d=%22M 20,8 L 25,8%22 style=%22fill:none;stroke:%23000000;stroke-linejoin:miter%22/><path d=%22M 32,29.5 C 32,29.5 40.5,25.5 38.03,19.85 C 34.15,14 25,18 22.5,24.5 L 22.51,26.6 L 22.5,24.5 C 20,18 9.906,14 6.997,19.85 C 4.5,25.5 11.85,28.85 11.85,28.85%22 style=%22fill:none;stroke:%23ffffff%22/><path d=%22M 11.5,30 C 17,27 27,27 32.5,30 M 11.5,33.5 C 17,30.5 27,30.5 32.5,33.5 M 11.5,37 C 17,34 27,34 32.5,37%22 style=%22fill:none;stroke:%23ffffff%22/></g></svg>',
+        'bQ': 'data:image/svg+xml,<?xml version=%221.0%22 encoding=%22UTF-8%22 standalone=%22no%22?>%0A<!DOCTYPE svg PUBLIC %22-//W3C//DTD SVG 1.1//EN%22 %22http://www.w3.org/Graphics/SVG/1.1/DTD/svg11.dtd%22>%0A<svg xmlns:svg=%22http://www.w3.org/2000/svg%22 xmlns=%22http://www.w3.org/2000/svg%22 version=%221.1%22 width=%2245%22 height=%2245%22 id=%22svg3128%22><defs/><g id=%22layer1%22><path d=%22M 8 12 A 2 2 0 1 1 4,12 A 2 2 0 1 1 8 12 z%22 style=%22opacity:1;fill:%23000000;fill-opacity:1;stroke:%23000000;stroke-width:1;stroke-linecap:round;stroke-linejoin:round;stroke-miterlimit:4;stroke-dasharray:none;stroke-opacity:1%22 id=%22path5571%22/><path d=%22M 9 13 A 2 2 0 1 1 5,13 A 2 2 0 1 1 9 13 z%22 transform=%22translate(15.5,-5.5)%22 style=%22opacity:1;fill:%23000000;fill-opacity:1;stroke:%23000000;stroke-width:1;stroke-linecap:round;stroke-linejoin:round;stroke-miterlimit:4;stroke-dasharray:none;stroke-opacity:1%22 id=%22path5573%22/><path d=%22M 9 13 A 2 2 0 1 1 5,13 A 2 2 0 1 1 9 13 z%22 transform=%22translate(32,-1)%22 style=%22opacity:1;fill:%23000000;fill-opacity:1;stroke:%23000000;stroke-width:1;stroke-linecap:round;stroke-linejoin:round;stroke-miterlimit:4;stroke-dasharray:none;stroke-opacity:1%22 id=%22path5575%22/><path d=%22M 9 13 A 2 2 0 1 1 5,13 A 2 2 0 1 1 9 13 z%22 transform=%22translate(7,-4.5)%22 style=%22opacity:1;fill:%23000000;fill-opacity:1;stroke:%23000000;stroke-width:1;stroke-linecap:round;stroke-linejoin:round;stroke-miterlimit:4;stroke-dasharray:none;stroke-opacity:1%22 id=%22path5577%22/><path d=%22M 9 13 A 2 2 0 1 1 5,13 A 2 2 0 1 1 9 13 z%22 transform=%22translate(24,-4)%22 style=%22opacity:1;fill:%23000000;fill-opacity:1;stroke:%23000000;stroke-width:1;stroke-linecap:round;stroke-linejoin:round;stroke-miterlimit:4;stroke-dasharray:none;stroke-opacity:1%22 id=%22path5579%22/><path d=%22M 9,26 C 17.5,24.5 30,24.5 36,26 L 38,14 L 31,25 L 31,11 L 25.5,24.5 L 22.5,9.5 L 19.5,24.5 L 14,10.5 L 14,25 L 7,14 L 9,26 z %22 style=%22fill:%23000000;fill-opacity:1;fill-rule:evenodd;stroke:%23000000;stroke-width:1px;stroke-linecap:butt;stroke-linejoin:round;stroke-opacity:1%22 id=%22path5581%22/><path d=%22M 9,26 C 9,28 10.5,28 11.5,30 C 12.5,31.5 12.5,31 12,33.5 C 10.5,34.5 10.5,36 10.5,36 C 9,37.5 11,38.5 11,38.5 C 17.5,39.5 27.5,39.5 34,38.5 C 34,38.5 35.5,37.5 34,36 C 34,36 34.5,34.5 33,33.5 C 32.5,31 32.5,31.5 33.5,30 C 34.5,28 36,28 36,26 C 27.5,24.5 17.5,24.5 9,26 z %22 style=%22fill:%23000000;fill-opacity:1;fill-rule:evenodd;stroke:%23000000;stroke-width:1px;stroke-linecap:butt;stroke-linejoin:round;stroke-opacity:1%22 id=%22path5583%22/><path d=%22M 11.5,30 C 15,29 30,29 33.5,30%22 style=%22fill:none;fill-opacity:0.75;fill-rule:evenodd;stroke:%23ffffff;stroke-width:1px;stroke-linecap:round;stroke-linejoin:round;stroke-opacity:1%22 id=%22path5585%22/><path d=%22M 12,33.5 C 18,32.5 27,32.5 33,33.5%22 style=%22fill:none;fill-opacity:0.75;fill-rule:evenodd;stroke:%23ffffff;stroke-width:1px;stroke-linecap:round;stroke-linejoin:round;stroke-opacity:1%22 id=%22path5587%22/><path d=%22M 10.5,36 C 15.5,35 29,35 34,36%22 style=%22fill:none;fill-opacity:0.75;fill-rule:evenodd;stroke:%23ffffff;stroke-width:1px;stroke-linecap:round;stroke-linejoin:round;stroke-opacity:1%22 id=%22path5589%22/></g></svg>',
+       'bR': 'data:image/svg+xml,<?xml version=%221.0%22 encoding=%22UTF-8%22 standalone=%22no%22?>%0A<!DOCTYPE svg PUBLIC %22-//W3C//DTD SVG 1.1//EN%22 %22http://www.w3.org/Graphics/SVG/1.1/DTD/svg11.dtd%22>%0A<svg xmlns=%22http://www.w3.org/2000/svg%22 version=%221.1%22 width=%2245%22 height=%2245%22><g style=%22opacity:1;fill:%23000000;fill-opacity:1;fill-rule:evenodd;stroke:%23000000;stroke-width:1.5;stroke-linecap:round;stroke-linejoin:round;stroke-miterlimit:4;stroke-dasharray:none;stroke-opacity:1%22 transform=%22translate(0,0.3)%22><path d=%22M 9,39 L 36,39 L 36,36 L 9,36 L 9,39 z %22 style=%22stroke-linecap:butt%22/><path d=%22M 12.5,32 L 14,29.5 L 31,29.5 L 32.5,32 L 12.5,32 z %22 style=%22stroke-linecap:butt%22/><path d=%22M 12,36 L 12,32 L 33,32 L 33,36 L 12,36 z %22 style=%22stroke-linecap:butt%22/><path d=%22M 14,29.5 L 14,16.5 L 31,16.5 L 31,29.5 L 14,29.5 z %22 style=%22stroke-linecap:butt;stroke-linejoin:miter%22/><path d=%22M 14,16.5 L 11,14 L 34,14 L 31,16.5 L 14,16.5 z %22 style=%22stroke-linecap:butt%22/><path d=%22M 11,14 L 11,9 L 15,9 L 15,11 L 20,11 L 20,9 L 25,9 L 25,11 L 30,11 L 30,9 L 34,9 L 34,14 L 11,14 z %22 style=%22stroke-linecap:butt%22/><path d=%22M 12,35.5 L 33,35.5 L 33,35.5%22 style=%22fill:none;stroke:%23ffffff;stroke-width:1;stroke-linejoin:miter%22/><path d=%22M 13,31.5 L 32,31.5%22 style=%22fill:none;stroke:%23ffffff;stroke-width:1;stroke-linejoin:miter%22/><path d=%22M 14,29.5 L 31,29.5%22 style=%22fill:none;stroke:%23ffffff;stroke-width:1;stroke-linejoin:miter%22/><path d=%22M 14,16.5 L 31,16.5%22 style=%22fill:none;stroke:%23ffffff;stroke-width:1;stroke-linejoin:miter%22/><path d=%22M 11,14 L 34,14%22 style=%22fill:none;stroke:%23ffffff;stroke-width:1;stroke-linejoin:miter%22/></g></svg>',
+       'bB': 'data:image/svg+xml,<?xml version=%221.0%22 encoding=%22UTF-8%22 standalone=%22no%22?>%0A<!DOCTYPE svg PUBLIC %22-//W3C//DTD SVG 1.1//EN%22 %22http://www.w3.org/Graphics/SVG/1.1/DTD/svg11.dtd%22>%0A<svg xmlns=%22http://www.w3.org/2000/svg%22 version=%221.1%22 width=%2245%22 height=%2245%22><g style=%22opacity:1;fill:none;fill-rule:evenodd;fill-opacity:1;stroke:%23000000;stroke-width:1.5;stroke-linecap:round;stroke-linejoin:round;stroke-miterlimit:4;stroke-dasharray:none;stroke-opacity:1%22 transform=%22translate(0,0.6)%22><g style=%22fill:%23000000;stroke:%23000000;stroke-linecap:butt%22><path d=%22M 9,36 C 12.39,35.03 19.11,36.43 22.5,34 C 25.89,36.43 32.61,35.03 36,36 C 36,36 37.65,36.54 39,38 C 38.32,38.97 37.35,38.99 36,38.5 C 32.61,37.53 25.89,38.96 22.5,37.5 C 19.11,38.96 12.39,37.53 9,38.5 C 7.65,38.99 6.68,38.97 6,38 C 7.35,36.54 9,36 9,36 z%22/><path d=%22M 15,32 C 17.5,34.5 27.5,34.5 30,32 C 30.5,30.5 30,30 30,30 C 30,27.5 27.5,26 27.5,26 C 33,24.5 33.5,14.5 22.5,10.5 C 11.5,14.5 12,24.5 17.5,26 C 17.5,26 15,27.5 15,30 C 15,30 14.5,30.5 15,32 z%22/><path d=%22M 25 8 A 2.5 2.5 0 1 1 20,8 A 2.5 2.5 0 1 1 25 8 z%22/></g><path d=%22M 17.5,26 L 27.5,26 M 15,30 L 30,30 M 22.5,15.5 L 22.5,20.5 M 20,18 L 25,18%22 style=%22fill:none;stroke:%23ffffff;stroke-linejoin:miter%22/></g></svg>',
+       'bN': 'data:image/svg+xml,<?xml version=%221.0%22 encoding=%22UTF-8%22 standalone=%22no%22?>%0A<!DOCTYPE svg PUBLIC %22-//W3C//DTD SVG 1.1//EN%22 %22http://www.w3.org/Graphics/SVG/1.1/DTD/svg11.dtd%22>%0A<svg xmlns=%22http://www.w3.org/2000/svg%22 version=%221.1%22 width=%2245%22 height=%2245%22><g style=%22opacity:1;fill:none;fill-opacity:1;fill-rule:evenodd;stroke:%23000000;stroke-width:1.5;stroke-linecap:round;stroke-linejoin:round;stroke-miterlimit:4;stroke-dasharray:none;stroke-opacity:1%22 transform=%22translate(0,0.3)%22><path d=%22M 22,10 C 32.5,11 38.5,18 38,39 L 15,39 C 15,30 25,32.5 23,18%22 style=%22fill:%23000000;stroke:%23000000%22/><path d=%22M 24,18 C 24.38,20.91 18.45,25.37 16,27 C 13,29 13.18,31.34 11,31 C 9.958,30.06 12.41,27.96 11,28 C 10,28 11.19,29.23 10,30 C 9,30 5.997,31 6,26 C 6,24 12,14 12,14 C 12,14 13.89,12.1 14,10.5 C 13.27,9.506 13.5,8.5 13.5,7.5 C 14.5,6.5 16.5,10 16.5,10 L 18.5,10 C 18.5,10 19.28,8.008 21,7 C 22,7 22,10 22,10%22 style=%22fill:%23000000;stroke:%23000000%22/><path d=%22M 9.5 25.5 A 0.5 0.5 0 1 1 8.5,25.5 A 0.5 0.5 0 1 1 9.5 25.5 z%22 style=%22fill:%23ffffff;stroke:%23ffffff%22/><path d=%22M 15 15.5 A 0.5 1.5 0 1 1 14,15.5 A 0.5 1.5 0 1 1 15 15.5 z%22 transform=%22matrix(0.866,0.5,-0.5,0.866,9.693,-5.173)%22 style=%22fill:%23ffffff;stroke:%23ffffff%22/><path d=%22M 24.55,10.4 L 24.1,11.85 L 24.6,12 C 27.75,13 30.25,14.49 32.5,18.75 C 34.75,23.01 35.75,29.06 35.25,39 L 35.2,39.5 L 37.45,39.5 L 37.5,39 C 38,28.94 36.62,22.15 34.25,17.66 C 31.88,13.17 28.46,11.02 25.06,10.5 L 24.55,10.4 z %22 style=%22fill:%23ffffff;stroke:none%22/></g></svg>',
+       'bP': 'data:image/svg+xml,<?xml version=%221.0%22 encoding=%22UTF-8%22 standalone=%22no%22?>%0A<!DOCTYPE svg PUBLIC %22-//W3C//DTD SVG 1.1//EN%22 %22http://www.w3.org/Graphics/SVG/1.1/DTD/svg11.dtd%22>%0A<svg xmlns=%22http://www.w3.org/2000/svg%22 version=%221.1%22 width=%2245%22 height=%2245%22><path d=%22m 22.5,9 c -2.21,0 -4,1.79 -4,4 0,0.89 0.29,1.71 0.78,2.38 C 17.33,16.5 16,18.59 16,21 c 0,2.03 0.94,3.84 2.41,5.03 C 15.41,27.09 11,31.58 11,39.5 H 34 C 34,31.58 29.59,27.09 26.59,26.03 28.06,24.84 29,23.03 29,21 29,18.59 27.67,16.5 25.72,15.38 26.21,14.71 26.5,13.89 26.5,13 c 0,-2.21 -1.79,-4 -4,-4 z%22 style=%22opacity:1;fill:%23000000;fill-opacity:1;fill-rule:nonzero;stroke:%23000000;stroke-width:1.5;stroke-linecap:round;stroke-linejoin:miter;stroke-miterlimit:4;stroke-dasharray:none;stroke-opacity:1%22/></svg>',
+};
 
-var init = function() {
+function svg_piece_theme(piece) {
+       return svg_pieces[piece];
+}
+
+function init() {
        unique = get_unique();
 
        // Load settings from HTML5 local storage if available.
-       if (supports_html5_storage() && localStorage['enable_sound']) {
-               set_sound(parseInt(localStorage['enable_sound']));
+       if (supports_html5_storage() && window['localStorage']['enable_sound']) {
+               set_sound(parseInt(window['localStorage']['enable_sound']));
        } else {
                set_sound(false);
        }
 
+       let admin_match = window.location.href.match(/\?password=([a-zA-Z0-9_-]+)/);
+       if (admin_match !== null) {
+               admin_password = admin_match[1];
+       }
+
        // Create board.
        board = new window.ChessBoard('board', {
                onMoveEnd: function() { board_is_animating = false; },
 
                draggable: true,
+               pieceTheme: svg_piece_theme,
                onDragStart: onDragStart,
                onDrop: onDrop,
                onSnapEnd: onSnapEnd
        });
-       $("#board").on('mousedown', '.square-55d63', mousedownSquare);
-       $("#board").on('mouseup', '.square-55d63', mouseupSquare);
+       document.getElementById("board").addEventListener('mousedown', mousedownSquare);
+       document.getElementById("board").addEventListener('mouseup', mouseupSquare);
 
+       if (window['inline_json']) {
+               let j = window['inline_json'];
+               process_update_response(j['data'], { 'get': (h) => j['headers'][h] });
+               delete window['inline_json'];
+       }
        request_update();
-       $(window).resize(function() {
+       window.addEventListener('resize', function() {
                board.resize();
                update_sparkline(displayed_analysis_data || current_analysis_data);
                update_board_highlight();
                redraw_arrows();
        });
-       $(window).keyup(function(event) {
+       new ResizeObserver(() => update_sparkline(displayed_analysis_data || current_analysis_data)).observe(document.getElementById('scoresparkcontainer'));
+       window.addEventListener('keyup', function(event) {
                if (event.which == 39) {  // Left arrow.
                        next_move();
                } else if (event.which == 37) {  // Right arrow.
                        prev_move();
                } else if (event.which >= 49 && event.which <= 57) {  // 1-9.
-                       var num = event.which - 49;
+                       let num = event.which - 49;
                        if (current_games && current_games.length >= num) {
                                switch_backend(current_games[num]);
                        }
@@ -2336,6 +2592,6 @@ var init = function() {
        window.addEventListener('hashchange', possibly_switch_game_from_hash, false);
        possibly_switch_game_from_hash();
 };
-$(document).ready(init);
+document.addEventListener('DOMContentLoaded', init);
 
 })();