The zombies want to steal your Christmas gifts, and you cannot let this happen! Get rid of these thug zombies by throwing snowballs at them! You can unlock better weapons as you progress.
Press 1 for primary gun, 2 for secondary gun, 3 for bombs, 4 for help call, 5 for bonus gun (if you get one). Use Q key to switch weapon, R to reload, CTRL for night vision, Space bar to zoom if the weapon has sniper.