Navigate your spaceship using the mouse. Click to fire. Destroy the asteroids. If they touch you or get to the bottom, you lose a life. You get three lives. Last as long as possible. Try and beat the high score.
I was having a lot of trouble with this until I found out the magical possibilities of the "Delete this Clone" block. Note: rapid fire (holding down the mouse) lags up the game, so try just clicking rapidly. Soundtrack: Chaoz Survivor, copied from ICantGetAGoodName's game Target Practice.