If the game freezes, just click inside it (games can get unresponsive if you click elsewhere on the page).
Can you outlast the zombie onslaught?
Arrow keys - Move.
Mouse - Aim & Shoot.
1-5 - Change Weapon.
Space bar - Activate Rage.
Survive the 30 waves of zombies and 2 bosses, buying upgrades with the money you earn from fighting. Can you make it to the end?