Pac-Man was one of the first extremely popular arcade games, and a major influence, if indirect and unwitting, on every computer game that followed. The reasons for its appeal are simple, it is colourful, cheerful and enjoyable; in short it is good, clean fun. Graphics date; fun is timeless. But the real key to its appeal is that it was the first video game to feature an actual character; this is the sense in which this game has paved the way for all which have followed. Pac-Man's anthropomorphic and aesthetic (i.e. "cute") qualities were particularly appealing to female audiences; this was the most popular game among girls at the time, and some sources suggest since. The after-effect was that the character itself became something of an icon; the character was the centre of a merchandising blitz. Pac-Man seemed to capture the public imagination more than any genuine cartoon character did; you could even make a claim for him being the Mickey Mouse of the 80s. I am a big fan of the Pac-Man phenomenon and have a book (Deborah Palicia's ["Pac-Man Collectibles") which details some 160 pages of related merchandising. There was everything from Bedsheets to a US Top 10 Record ("Pacman Fever" by Buckner and Garcia) and from Pasta to an animated cartoon series. It's fascinating how far such a one dimensional concept has spread. The most telling item is an advert for the game "Super Pac-Man" with a hero who "fights a never ending battle to eat row of fruit"! A lot of talented and creative people have worked on keeping this simple concept and character popular for nearly three decades, and millions more have enjoyed it.
