world

By far the most commonly used coordinate system. Actor.position uses world coordinates. At the start of the game, (0,0) is probably at the center of the view, but if your games lets you scroll that will change.

Similarly, at the start of the game, the Y axis points upwards. But you can rotate the view, so that it points in any direction.

In theory, world coordinates could be measured in pixels, feet, meters... In practice, most games set a nominal size for the game, and then a scaling factor is applied so that this nominal size fits within the window.

For example, suppose I set a nominal size of (800x600), and the game's window is 1600 x 1200 pixels, then each world unit would be 2 pixels. i.e. images would be scaled by a factor of 2.

Try to ensure that you graphics do NOT end up being scaled by a factor close to 1, as that will often make the look blurry.

StageView and ActView convert between window and world coordinates using StageOrActView.sceneToWorld and StageOrActView.worldToScene matrices.

Actor converts between world and local coordinates using Actor.worldToLocal and Actor.localToWorld matrices.