Shoot the zombies as they pop up, the zombies will grow faster as the game continues. 40 kills is needed to win the game.
Thanks to ZX2613Z for the original project. The changes I made: you needed 250 kills to win, i made it 40 (this is an unrealistic number, no-one would do this), to get to hardness 2 you needed 50 kills, I made it 20, to get hardness 3 you needed 200 kills, I made it 30, and the zombie spawn rate was 2 seconds, I made it 0.8 seconds.
