You have gun, face waves and waves of evil badguys, obtain a powerup here and there
highest score 29445. There's really no strategy to it. Sit in a corner, blast anything that moves, if possible, go and get that flamethrower/icegun/super shield (those are the only weapons worth risking your life for, in addition to all the life gaining stuff), wait till the doors become unblocked and then enter the next room. Just pure carnage.
And kill the chickens before they get to you.
http://www.flashring.com/8ga.shtml