Press the Green Flag TWICE to start. Use the up and down arrow keys to move around, and the left and right keys to turn. Press the space key to shoot. There are two guns to choose from, by pressing the 1 and 2 keys. The Green Zombies take 1 shot to kill, and the Orange Zombies take 2 shots to kill.
Thanks to Warfame's video series on the shooter game. That helped a lot. NOTE: This is the experimental game, so there are bugs
