How would you change this sketch?

https://openprocessing.org/sketch/2857202

how would you change this sketch so that it got more interesting or funny or contrasted what would you do to it?

You can change color or form of the rect throughout or upon reflection

You can have 2 or 3 balls that reflect with each other

You can have a rect on the lower side of the screen; only the rect reflects, not the screen border. Steer rect with mouse.