It's just you and your shotgun against the relentless insane shapes. Shoot those suckers down.
Use the left and right arrow keys to move your character. Aim and shoot with the mouse.
It is very important to collect the fallen ammo. Get more ammo by shooting 2 or more enemies at the same time. You can also collect fallen Nuke and Speed-Up powerups.
There are 21 levels in all.