Mappy (マッピー, Mappī) is a 1983 arcade game by Midway Games (until Namco Classic Collection vol.1 is released, it was made by Namco). In the United States, it was manufactured and distributed by Bally/Midway. Mappy is a side-scrolling platformer that features cartoon-like characters, primarily cats and mice. The game's main character itself is a mouse. Mappy runs on Namco Super Pac-Man hardware, modified to support horizontal scrolling. The name "Mappy" is likely derived from mappo, a Japanese slang term (slightly insulting) for a policeman.

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. The items are:

• Radio (100 points)
• Television (200 points)
• Computer (300 points)
• Mona Lisa (400 points)
• Safe (500 points)

The items come in pairs; should Mappy get paired items one after another, the point values of the second matching item gets a multiplier. The second item of a pair will blink if retrieving it will yield a multiplier. The more the player retrieves matching items without dying, the bigger the multiplier gets. Therefore, ideally a player will start with the lowest value item (tape player for 100 + 100 × 2) and proceed to the highest value item (safe for 500 + 500 × 6) in order to get the highest value items with the biggest multiplier, for a total of 8500 points.

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 they pass in the air, Mappy is unharmed by the cats, but should Mappy run into a cat anywhere else, he will lose a life.

The trampolines will break if Mappy bounces on them four times in a row. The trampolines change color depending on how many times Mappy has used them without a rest: green (zero bounces), blue (one bounce), yellow (two bounces), red (three bounces). A red trampoline will break if Mappy attempts it again. If a trampoline breaks and there is another trampoline below, Mappy will live. If there is either nothing or a floor under the broken trampoline, Mappy will lose a life. To reset a trampoline, Mappy must touch a floor. Bouncing on a trampoline is worth 10 points.

In addition to Meowkies, the boss cat Nyamco also roams around. The name "Nyamco", besides being a play on "Namco", comes from nyanko, the Japanese equivalent of "kitty cat". Nyamco was renamed "Goro" in the U.S. release. He is faster, but less aggressive than the Mewkies. Throughout the levels, Nyamco hides behind the different recoverable objects. Should Mappy recover an item which Nyamco is hiding behind, the player gets a bonus of 1000 points for having caught Nyamco in the act. Nyamco hides behind an object for only three seconds. Nyamco is always a single cat in each level, but the Meowkies appear three to a group for the first set of levels before the first bonus stage, four to a group for the next set of levels in between bonus levels, five to a group for the next set of levels, and so on.

Many of the hallways have doors which Mappy can slam open or shut to temporarily knock out the Mewkies or Nyamco. Some of these are special "microwave doors" which release a rainbow-colored wave which sweeps away any cat in its path off the edge of the screen and out of the house. The first two Mewkies are each worth 200 points, and each additional Mewky beyond the second is worth 400 points; Nyamco counts as a Mewky plus a multiplier of two. Any cat that is swept away reappears after a short while, jumping from the top center opening in the roof.

A level is completed when all the loot is retrieved. If Mappy tarries too long, a "Hurry" sign appears after which the music and the cats speed up, and more Mewkies are added (two will appear ready to drop as the Mewkies normally do immediately following the hurry message, and more Mewkies can arrive later on). If the player waits too long after this, the "Gosenzo" coin (a blue disk shape with Nyamco's face on it) will drop onto the top-middle platform and chase Mappy in a manner similar to the Mewkies, but more effectively. The "Gosenzo" coin can harm Mappy even if he is in the air.

The third level and every fourth level after that is a bonus round. Mappy, unbothered by any cats, must bounce across a series of trampolines, popping fifteen different suspended red balloons, with a "Nyamco" along the way. A bonus is awarded if all the balloons are popped before the music ends, at which time the level will end as long as a player has not previously fallen through a trampoline onto nothing, which would abruptly end the bonus level. The Nyamco balloon will break any trampoline and will grab one balloon above him for Mappy. In addition to 10 points for each trampoline bounce, each red balloon is worth 200 points, the large blue Nyamco balloon is worth 2,000 points, and collecting all of the balloons is worth a bonus of an additional 5,000 points.

After every bonus round, a new feature is added to the gameplay. After the first bonus round (Level 3), the attics of the houses are available for Mappy to run inside (though there isn't anything in them). After the next bonus level (7), the following levels (eighth to tenth) have bells over the trampoline wells, which Mappy can hit so that it drops and temporarily freezes in place any cats below, for 300 points each (1,000 points for stunning Nyamco). Starting from these stages, the "Hurry" sign will also appear earlier and earlier. After the third bonus round (11), small "rainbow floors" appear in some of the hallways. After Mappy runs on these mini-floors, they vanish, leaving a hole in the floor. If the meowkies or Nyamco run over this newly formed hole, they fall to the level below and are stunned, but if Mappy falls through, he'll die because there is no trampoline below to catch him. In addition to these rainbow floors, dead-end hallways are included. On both the left and right side of the houses, one hallway leads to a safe to retrieve, as well as the wall. If Mappy tries to get the safe but is cornered by a Meowkie, Mappy is assured certain death.

As there are 256 rounds, like in Pac-Man and other 8-bit arcade games, the last round's play is normal, but harder than usual. When the player finishes the round, which is also known as "round 0," the first round appears again.