Slime Atari-Ball by by Danny Miller, Kevin Murray, Kristina Makarova.

Release notes:

A demo of two AI characters will play when starting the game. Press spacebar to begin two player mode. Spacebar again for one player mode against the AI. Use the arrow keys to move and the spacebar to change player modes (1-2 player).

http://www.bogost.com/games/student_atari_games.shtml