Upon starting a level, the player has a menu where he can choose what weapon to equip this attempt. It defaults to assault rifle for his first ever play, and after that to whatever weapon the player had last equipped.

All characters are frozen until the player starts moving. At that point, player moves around with WASD. Player uses the mouse to choose what direction his gun is pointed, and fires healing bullets with M1. Player has a knife melee attack fired with M2.

Player can press Escape to bring up a menu to adjust settings or quit the game.