Move around your mouse to move the orange square and shoot out orange paint by clicking. You gradually run out of paint as you shoot, but you can regain paint by running over paint canisters. As you play, purple squares will advance toward you and spread purple paint where they move. If the purple squares touch anything orange, they explode in a gush of purple ink. But if you (the orange square) touch anything purple, you lose the game.
If you want more of a challenge, you can try to play WITHOUT touching any paint canisters!