This starter project begins with ONE working sprite -- the orange ball, controlled by the arrow keys. To complete the project, I had to copy that code to the other balls & modify each so it REFLECTS the orange ball's movements -- one in each quadrant.
Thanks to DrShoe32! This is a GREAT math+code project! It forces you to think carefully about reflection, x/y coordinates, and+/- values. Bonus: because it's live coding, you can TEST as you go, and make use of what you know about TRANSLATION and MOTION. It's almost like debugging a video game. Fun! :)