Click to drag either the red starting point or the wall. Use the arrows keys to turn the last object you clicked. The ball will start moving when you press the green flag. It is very buggy. (not as buggy as at launch though (as of December 13 2024)) Comment if the anything wrong (and I know there's going to be something wrong) and how I can fix it.
TurboWarp (makes it run faster while still giving the same results): https://turbowarp.org/1050408036?fps=60