If the game freezes, just click inside it (games can get unresponsive if you click elsewhere on the page).
a Cave with 300 people need your defense against all the approaching Zombies. If You miss a zombie alive in the cave, then they will return with at least 10 more zombified people. It may become impossible to stay alive
W,A,S,D / Arrow Keys - Move.
Mouse - Aim / Shoot.
R - Reload.
1-4 - Switch weapon.