When you press the flag, zombies will start spawning. You can hit the space bar to shoot, up arrow to move around, and the left and right arrows to move in their respective directions. Hitting a zombie 3 times will kill it, and after 60 seconds they will all disappear.
I've noticed the clones get slightly glitchy if too many get close to the player, so be careful of that. P.S. This is my first project I'm really proud of, and it would mean a lot if you liked and favorite it :3