From the game configuration screen (dubbed Mutation Central), players begin a session by creating a name, choosing one of the four beasts, and choosing a game mode. Monster mode provides an unlimited supply of atomic energy (which is used for bringing destruction to the countryside) but provides only one life for your beast with no possibility of gaining additional lives. Arcade mode gives the player three lives to begin, but provides only a limited amount of atomic energy. There are also settings for black-and-white play, for the full effect of B-movie flair.

Once the options are selected, the action begins with your immense monster standing in a bleak desert landscape. The objective of each level is to flatten every building around while surviving the onslaught of fighter planes, tanks, rocket soldiers, and gun emplacements the puny humans will use in their attempt to stop total annihilation. To accomplish this goal, each monster is equipped with a number of attacks, from a ranged assault with limited damage potential, to close-up attacks capable of leveling whole city blocks with devastating results.

While most of the attacks are nearly identical from creature to creature, their aesthetics vary. While the Brain from Beyond Infinity can deliver a powerful Mind Whomp on close-ranged targets, Reptomicus belches a jet of powerful flames, which has about the same effect. Each monster has one unique ability that separates their powers a bit: She-Beast can send out an ear-shattering scream that stuns enemies and keeps them from firing for a limited time, while Reptomicus can snatch up fleeing people and eat them for a small boost in health. Brain from Beyond Infinity’s awesome Insanity Ray provides a good chuckle by changing fleeing citizens and soldiers into defenseless stuffed animals.

Sprinkled around each level are color-coded power-ups represented by floating atoms. Power-up abilities include increases in life or atomic energy, double damage for a period of time, an extra life, and invulnerability. These are all useful when barrages of bombers and convoys of tanks make stomping and smashing difficult on later levels. Atomic energy is necessary for every form of attack, and luckily recharges when depleted completely. Attack powers use varying amounts of atomic energy, depending on their destructive potential.

As the action progresses, the weapons used against the giant monsters changes. Machine-gun tanks get rocket upgrades while propeller driven fighter planes are grounded to let missile-wielding jet fighters take a shot at the unstoppable monsters. Ground troops, typically police officers and soldiers, fire shots that cause minimal damage. Most of these can be dispatched by stepping on them, or with a bit of overkill, unleashing a powerful close-ranged attack. There are tougher ground forces that come at later stages, including missile emplacements, stationary gun turrets, mobile tanks, missile tanks, and bio-warriors with short-ranged but powerful bursts of energy.