The game was originally named "Puckman" but this name was no-good in the US, as it resembled another well known word too much. So it was changed to Pac-Man for the US and European release.
The game-plot is simple, it's a maze with 4 ghosts who hunt our hero Pac-Man, Pac-Man has to eat all the pills in the maze path. There's 4 power pills that makes Pac-Man able to eat the ghosts. The Ghosts respawn after a little while in the "prison" in the middle of the maze. When Pac-Man moves on areas where there are no pills to eat, he moves 20% faster, or put the other way: the speed is reduced by 20% when he eat pills. The ghosts move 50% slower when Pac-Man eat the power-pill.
HighScore:
The score is calculated pretty simple, each pill he eats is worth 10 points(there's a total of 240
pills), each super pill is worth 50(4 of them). During the short intervals when you can eat
the ghosts they are worth 200,400,800, and 1600 points each. (The first ghost is 200, the next is 400 etc).
When the level is clear, the next level starts. There was a total of 256 levels. Where the 256 is the final, and has never been completed(on the original arcade box) due to a bug in the console.
AI:
Pac-Man is the player character in the game, the ghosts were named Binky, Inky, Pinky and Clyde in
the English-international version. You might think that the AI in Pac-Man is a simple follow and evade routine.
Well.. it's not, the AI in Pac-Man was state-of-the-art back in 1980. Each ghost had it's own AI routine
and strategy.
The japanse names of the ghosts, had some clues towards how their strategy worked, however in the international release the names gave no clues to the strategy.
The red ghost was named Inky
The blue ghost was named Blinky
The pink ghost was named Pinky
The orange ghost was named Clyde
Inky follows Pac-Man directly with a tracking algorithm.
Blinky goes to the opposite end of the corridor Pac-Man is in.
Pinky just moves in his general direction and is faster than other ghosts.
Clyde moves randomly, but generally into the direction of Pac-Man, Clyde is also slower than
the other ghosts.
Blinky tries to avoid you at first, but if you chase him too much (eat him) he will get mad at you and start following you just like Inky.
A few other points to make out, when Pac-Man turns in corners, Pac-Man turns a little faster than the ghosts, so it's possible to out manouver them by doing a few turns.
There's nothing random in the AI routine. The ghosts AI is based on a deterministic AI routine. Each Ghost will allways respond the same way to a given siuasion, so it's possible to learn and know what the ghost will do next.