In Mountain Maniac you control a man with a hammer whose single aim is to destroy the town at the foot of a mountain for points. He does this by smashing boulders with his instrument of doom, sending them down the mountain Pachinko-style while crushing everything that stands in its way. Occasionally the police force or a yeti might try and stop him, but you can use the mallet to protect yourself by swinging it at them as well.

There is a certain percentage of town destruction that you must achieve to pass each level, and failure to do so equates to a loss of a precious life. An online high score submission feature is included as well, although players must first register for an Adult Swim account before they can post their best achievements up on the site.