There are some variables that are always defined like
"frame" which stores the number of frames that have gone by since the scene producer started,
"mouse_x" and "mouse_y" which reflect the X and Y position of the mouse at all times relative to the scene coordinate system (requires interaction aware consumer like screen_consumer),
- "timeline_frame" which differs from "frame" in that it can rewind and jump, depending on where the timeline is at the moment and
+ "timeline_frame" which differs from "frame" in that it can rewind and jump, depending on where the timeline is at the moment,
+ "fps" which always contains the framerate of the scene and
"scene_width" and "scene_height" which contains the dimensions of the scene coordinate system.
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