If the game freezes, just click inside it (games can get unresponsive if you click elsewhere on the page).
You are under assault from zombies and must protect your adventure against the inbound group. They will assault the adventure from both the area and air, so be ready to go up the structure in order to destroy the traveling zombie hits and mythical beasts. Go for headshots and get additional revenue to update your weapons between stages.
Mouse - Aim / Shoot.
Mouse Wheel - Change weapon.
1-3 - Change position.