You have to help the two cats to defend their positions form the waves of pot smoking zombies. Shoot the zombies and don't let them get close to you as they'll start to intensively smoke pot and get you stoned and defenseless. Ammo is limited so do not give your partner the same type of weapon as you are using. Also some weapons are better suited for a type of enemy than others. Upgrade your guns and don't forget to equip your AI buddy.

Mouse to aim and shoot. 1-3 to change guns.