Rumble Box is a great freeware beat em up game which uses characters made of cubes and balls. Controls are pretty easy to figure out. Use the arrow keys to move your character, double tab forward for a dash, press the spacebar to hit and use Control to grab. The enemies enter the level through doors that appear in the walls that limit the box that you are fighting in. Defeated enemies stay in the level dispelled in the objects that they were composed off.
