Pac-Rat is a maze-style, puzzle arcade game similar to class Pac-Man. A rat is attempting to eat cheddar cheese wedges and wheels in mazes across six levels. Yet, it's threatened by several prowling cats. The player's task is to help the rat stay alive long enough to eat all the cheese.
As soon as children's voices yell out, "Get ready... go!," the player must use strategy and elements in each maze to prevent the cats from catching the rat. They can simply use observation to direct the rat away from any area that has a cat in it. Since the cats hunt the rat as well, the player can direct the rat to eat one of several wheels to receive a power up that turns the rat temporarily into a green monster that eats cats. When the rat transforms, the cats scream and run away. When it eats one of them, the dead cat's ghost is forced to go back to its home area to resurrect itself, which gives the player time to direct the rat to eat more cheese wedges.
Pac-Rat offers two additional helpful game features. It offers portal-style gates on the left and right sides of each maze that the player can use to transport the rat rapidly from one side to the other side. It also provides three lives for the rat. When only one life remains, the game allows the player to start a level over from the beginning without forcing them to play every level again.