Yeah, I’m answering this question myself. Because I will inevitably forget and then search the forums again. Hi, future me!
Assume you have set your dimensions as 960x540 in game.project. You’re playing on a 1920x1080 monitor. If you place your cursor in the top right, the position of your input would be:
action.x,y → 960 x 540
action.screen_x,y → 1920 x 1080
So, to help me think about it, you might call action.xy something like “action.game_project_xy” instead, since the input is translated to fit your game project dimensions.
BONUS:
In Orthographic, “screen” co-ordinates refers to action.xy, and “window” co-ordinates refers to action.screen_xy. This is explained in the docs.
If anyone else has any other tips to add, feel free. I’m always struggling to conceptualise input on different resolutions and stretched game windows, etc, so anything will be helpful.