WASD to move
R to reload
Left click to shoot
Powerups - Heart gives back 1/3 max hp, Shotgun adds extra bullets for 12 seconds, Reload Badge cuts reload time in half for 10 seconds, Flame Badge converts weapon to close range high dps flamethrower
Permanent upgrades - every 150 kills pick from + 5 max hp or 2 max shield(50% chance at either), +10 max ammo, or + 25 move speed
Difficulties:
Normal - slow zombies with a lower spawn rate who do 1 damage per hit and die to 1 bullet
Hard - zombies are faster with a slightly higher spawn rate ceiling and have doubled stats
Nightmare - zombies are freakishly fast with tripled stats and the highest spawn rate cap