Mappy is a platform game for the Nintendo Entertainment System where players control Mappy, a police mouse on a mission to recover stolen items from the Mewkies, a group of cats. Navigating a six-floor mansion filled with hallways, players use a joystick to move Mappy and a button to open doors, avoiding cat enemies while collecting treasures hidden throughout the mansion.
The player guides Mappy the police mouse through the mansion of the cats called Mewkies (Meowky in the U.S. version) 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 in which the stolen items are stashed.