If the game freezes, just click inside it (games can get unresponsive if you click elsewhere on the page).
The goal of the action game 'Shotgun VS Zombies' is fairly straightforward: Run around, kill all the undead and buy cool upgrades in the shop.
A,D / Left,Right Arrow Keys - Move.
W / Up Arrow Key - Jump.
X,L - Shoot.
Z.,K - Melee Attack.