+typedef uint64_t Key;
+typedef uint64_t Bitboard;
+
+constexpr int MAX_MOVES = 256;
+constexpr int MAX_PLY = 128;
+
+/// A move needs 16 bits to be stored
+///
+/// bit 0- 5: destination square (from 0 to 63)
+/// bit 6-11: origin square (from 0 to 63)
+/// bit 12-13: promotion piece type - 2 (from KNIGHT-2 to QUEEN-2)
+/// bit 14-15: special move flag: promotion (1), en passant (2), castling (3)
+/// NOTE: EN-PASSANT bit is set only when a pawn can be captured
+///
+/// Special cases are MOVE_NONE and MOVE_NULL. We can sneak these in because in
+/// any normal move destination square is always different from origin square
+/// while MOVE_NONE and MOVE_NULL have the same origin and destination square.
+
+enum Move : int {
+ MOVE_NONE,
+ MOVE_NULL = 65
+};
+
+enum MoveType {
+ NORMAL,
+ PROMOTION = 1 << 14,
+ ENPASSANT = 2 << 14,
+ CASTLING = 3 << 14
+};
+
+enum Color {
+ WHITE, BLACK, COLOR_NB = 2
+};
+
+enum CastlingSide {
+ KING_SIDE, QUEEN_SIDE, CASTLING_SIDE_NB = 2
+};
+
+enum CastlingRight {
+ NO_CASTLING,
+ WHITE_OO,
+ WHITE_OOO = WHITE_OO << 1,
+ BLACK_OO = WHITE_OO << 2,
+ BLACK_OOO = WHITE_OO << 3,
+ WHITE_CASTLING = WHITE_OO | WHITE_OOO,
+ BLACK_CASTLING = BLACK_OO | BLACK_OOO,
+ ANY_CASTLING = WHITE_CASTLING | BLACK_CASTLING,
+ CASTLING_RIGHT_NB = 16
+};
+
+enum Phase {
+ PHASE_ENDGAME,
+ PHASE_MIDGAME = 128,
+ MG = 0, EG = 1, PHASE_NB = 2
+};
+
+enum ScaleFactor {
+ SCALE_FACTOR_DRAW = 0,
+ SCALE_FACTOR_NORMAL = 64,
+ SCALE_FACTOR_MAX = 128,
+ SCALE_FACTOR_NONE = 255
+};
+
+enum Bound {
+ BOUND_NONE,
+ BOUND_UPPER,
+ BOUND_LOWER,
+ BOUND_EXACT = BOUND_UPPER | BOUND_LOWER
+};
+
+enum Value : int {
+ VALUE_ZERO = 0,
+ VALUE_DRAW = 0,
+ VALUE_KNOWN_WIN = 10000,
+ VALUE_MATE = 32000,
+ VALUE_INFINITE = 32001,
+ VALUE_NONE = 32002,
+
+ VALUE_MATE_IN_MAX_PLY = VALUE_MATE - 2 * MAX_PLY,
+ VALUE_MATED_IN_MAX_PLY = -VALUE_MATE + 2 * MAX_PLY,
+
+ PawnValueMg = 136, PawnValueEg = 208,
+ KnightValueMg = 782, KnightValueEg = 865,
+ BishopValueMg = 830, BishopValueEg = 918,
+ RookValueMg = 1289, RookValueEg = 1378,
+ QueenValueMg = 2529, QueenValueEg = 2687,
+
+ MidgameLimit = 15258, EndgameLimit = 3915
+};
+
+enum PieceType {
+ NO_PIECE_TYPE, PAWN, KNIGHT, BISHOP, ROOK, QUEEN, KING,
+ ALL_PIECES = 0,
+ PIECE_TYPE_NB = 8
+};
+
+enum Piece {
+ NO_PIECE,
+ W_PAWN = 1, W_KNIGHT, W_BISHOP, W_ROOK, W_QUEEN, W_KING,
+ B_PAWN = 9, B_KNIGHT, B_BISHOP, B_ROOK, B_QUEEN, B_KING,
+ PIECE_NB = 16
+};
+
+extern Value PieceValue[PHASE_NB][PIECE_NB];
+
+enum Depth : int {
+
+ ONE_PLY = 1,
+
+ DEPTH_ZERO = 0 * ONE_PLY,
+ DEPTH_QS_CHECKS = 0 * ONE_PLY,
+ DEPTH_QS_NO_CHECKS = -1 * ONE_PLY,
+ DEPTH_QS_RECAPTURES = -5 * ONE_PLY,
+
+ DEPTH_NONE = -6 * ONE_PLY,
+ DEPTH_MAX = MAX_PLY * ONE_PLY
+};
+
+static_assert(!(ONE_PLY & (ONE_PLY - 1)), "ONE_PLY is not a power of 2");
+
+enum Square : int {
+ SQ_A1, SQ_B1, SQ_C1, SQ_D1, SQ_E1, SQ_F1, SQ_G1, SQ_H1,
+ SQ_A2, SQ_B2, SQ_C2, SQ_D2, SQ_E2, SQ_F2, SQ_G2, SQ_H2,
+ SQ_A3, SQ_B3, SQ_C3, SQ_D3, SQ_E3, SQ_F3, SQ_G3, SQ_H3,
+ SQ_A4, SQ_B4, SQ_C4, SQ_D4, SQ_E4, SQ_F4, SQ_G4, SQ_H4,
+ SQ_A5, SQ_B5, SQ_C5, SQ_D5, SQ_E5, SQ_F5, SQ_G5, SQ_H5,
+ SQ_A6, SQ_B6, SQ_C6, SQ_D6, SQ_E6, SQ_F6, SQ_G6, SQ_H6,
+ SQ_A7, SQ_B7, SQ_C7, SQ_D7, SQ_E7, SQ_F7, SQ_G7, SQ_H7,
+ SQ_A8, SQ_B8, SQ_C8, SQ_D8, SQ_E8, SQ_F8, SQ_G8, SQ_H8,
+ SQ_NONE,
+
+ SQUARE_NB = 64
+};
+
+enum Direction : int {
+ NORTH = 8,
+ EAST = 1,
+ SOUTH = -NORTH,
+ WEST = -EAST,
+
+ NORTH_EAST = NORTH + EAST,
+ SOUTH_EAST = SOUTH + EAST,
+ SOUTH_WEST = SOUTH + WEST,
+ NORTH_WEST = NORTH + WEST
+};
+
+enum File : int {
+ FILE_A, FILE_B, FILE_C, FILE_D, FILE_E, FILE_F, FILE_G, FILE_H, FILE_NB
+};
+
+enum Rank : int {
+ RANK_1, RANK_2, RANK_3, RANK_4, RANK_5, RANK_6, RANK_7, RANK_8, RANK_NB
+};
+
+
+/// Score enum stores a middlegame and an endgame value in a single integer (enum).
+/// The least significant 16 bits are used to store the middlegame value and the
+/// upper 16 bits are used to store the endgame value. We have to take care to
+/// avoid left-shifting a signed int to avoid undefined behavior.
+enum Score : int { SCORE_ZERO };
+
+constexpr Score make_score(int mg, int eg) {
+ return Score((int)((unsigned int)eg << 16) + mg);