The player guides Mappy the police mouse through the mansion of the cats called Meowkies (Mewkies in Japan) to retrieve stolen goods. The player uses a left-right joystick to move Mappy and a single button to operate doors. The mansion has six floors of hallways (four or five in some other versions) in which the stolen items are stashed. Mappy and the cats move between floors by bouncing on trampolines at various places in the house. Both Mappy and the cats can land on a floor on the way up, but not on the way down. When Mappy passes cats in the air, Mappy is unharmed, but if Mappy runs into a cat anywhere else, he will lose a life. The trampolines break when Mappy bounces on them four times in a row, and the trampolines change color depending on how many times Mappy has used them without a rest. In addition to the Meowkies, the boss cat Goro (Nyamco in Japanese) also roams around. He is faster but less aggressive than the Meowkies. Throughout the levels, Goro hides behind the different recoverable objects. If Mappy recovers an item which Goro is hiding behind, the player receives 1000 points in addition to the score for the item.