Sure, here's a basic implementation of Pac-Man as a single HTML file using JavaScript:
In this implementation, Pac-Man is represented by a yellow circle (`div` with class "pacman") inside a game board (`div` with id "game-board"). The player can control Pac-Man's movement using the arrow keys. The game board has a fixed size of 480x480 pixels, and Pac-Man can move in increments of 40 pixels in each direction.