Pac Man 2021 is a title which has little to do with the gameplay of Bandai Namco's Pac-Man series. The player controls a candy-striped oblong object, called a "nanobot", and is tasked with rolling over ghosts before they catch the "Pac Men". The player is also supposed to avoid rolling over the Pac Men themselves. A stage is completed when all of the ghosts have been destroyed and the game is lost if all of the Pac Men are killed.
Scoring is based on rolling over the ghosts (+50 points), their "power-ups" (+20 points), and an infected Pac Man (+200 points). If a ghost collides with a Pac Man, it will turn the Pac Man blue and after a short time, the Pac Man will erupt into two ghosts. A player will lose points if they roll over a Pac Man (-100 points) or the Pac Man power-ups (-20), which allow Pac Men to turn orange and eat ghosts.
The game ends when level 11 is reached, as the game fails to load the stage outright.