In each of the twenty caverns, each one screen in size, are several flashing objects, which the player must collect before Willy's oxygen supply runs out. Once the player has collected the objects in one cavern, they must then go to the now-flashing portal, which will take them to the next cavern. The player must avoid enemies, listed in the cassette inlay as "...Poisonous Pansies, Spiders, Slime, and worst of all, Manic Mining Robots..." which move along predefined paths at constant speeds. Willy can also be killed by falling too far, so players must time the precision of jumps and other movements to prevent such falls or collisions with the enemies. Extra lives are gained every 10,000 points, and the game ends when the player has no lives left. Above the final portal is a garden. To the right is a house with a white picket fence and red car parked in front. To the left is a slope leading to backyard with a pond and tree; a white animal, resembling a cat or mouse, watches the sun set behind the pond. Upon gaining his freedom, the game restarts from the first level with no increase in difficulty.

The in-game music is In the Hall of the Mountain King from Edvard Grieg's music to Henrik Ibsen's play Peer Gynt. The music that plays during the title screen is an arrangement of The Blue Danube.