If the game freezes, just click inside it (games can get unresponsive if you click elsewhere on the page).
Your time-machine has just sent you to a violent past; can you survive?
WSAD or Arrows for moving.
Mouse for shoting.
“E” for using switches and moving ragdolls. Numbers or mouse wheel to change guns.
“P” for pause.
“num0”/“Enter”/“G” for using grenades.