The player controls Pac-Man through a maze, eating pac-dots. When all dots are eaten, Pac-Man is taken to the next stage, between some stages one of three intermission animations plays. Four enemies (Blinky, Pinky, Inky and Clyde) roam the maze, trying to catch Pac-Man. If an enemy touches Pac-Man, a life is lost. When all lives have been lost, the game ends. Pac-Man is awarded a single bonus life at 10,000 points by default—DIP switches inside the machine can change the required points or disable the bonus life altogether. Near the corners of the maze are four larger, flashing dots known as power pellets that provide Pac-Man with the temporary ability to eat the enemies. The enemies turn deep blue, reverse direction and usually move more slowly. When an enemy is eaten, its eyes remain and return to the center box where it is regenerated in its normal color. Blue enemies flash white before they become dangerous again and the length of time for which the enemies remain vulnerable varies from one stage to the next, generally becoming shorter as the game progresses. In later stages, the enemies go straight to flashing, bypassing blue, although they still reverse direction when a power pellet is eaten.Pac-Man was designed to have no ending – as long as the player keeps at least one life, he or she should be able to play the game indefinitely. However, a bug keeps this from happening: Normally, no more than seven fruits are displayed at the bottom of the screen at any one time. But when the internal level counter, which is stored in a single byte, reaches 255, the subroutine that draws the fruits erroneously "rolls over" this number to zero, causing it to try to draw 256 fruits instead of the usual seven. This corrupts the bottom of the screen and the entire right half of the maze with thumb|300px|right|Pac-Man gameplay.seemingly random symbols, making it impossible to eat enough dots to beat the level. Because this effectively ends the game, this "split-screen" level is often referred to as the "kill screen". Emulators and code analysis have revealed what would happen should this 255th level be cleared: The fruits and intermissions would restart at level 1 conditions, but the enemies would retain their higher speed and invulnerability to power pellets from the higher stages.
The game was developed primarily by a young Namco employee named Tōru Iwatani over the course of a year, beginning in April 1979, employing a nine-man team. It was based on the concept of eating, and the original Japanese title was Pakkuman (パックマン?), inspired by the Japanese onomatopoeic slang phrase paku-paku taberu (パクパク食べる?), where paku-paku describes (the sound of) the mouth movement when widely opened and then closed in succession.
Although Iwatani has repeatedly stated that the character's shape was inspired by a pizza missing a slice, he admitted in a 1986 interview that this was a half-truth and the character design also came from simplifying and rounding out the Japanese character for mouth, kuchi (口). Iwatani attempted to appeal to a wider audience—beyond the typical demographics of young boys and teenagers. This led him to add elements of a maze, as well as cute ghost enemy characters. The result was a game he named Puck Man.Later in 1980, the game was picked up for manufacture in the United States by Bally division Midway, which changed the game's name from Puck Man to Pac-Man in an effort to avoid vandalism to the letter 'P'. The cabinet artwork was also changed.