abstract_ball

- "If touching edge, bounce" -- a Mr. Y version of "If on edge, bounce"
- "ball bounce" -- a Mr. Y ABSTRACTION of the entire ball bouncing procedure logic, calls "if touching edge, bounce," and has an argument for the speed the ball will move in the program
- "alt_move" and "alt_move_neg" are separate Mr. Y version abstractions of the "move ____ steps" SNAP! function.  "alt_move" moves to the right, and "alt_move_neg" moves to the left.