Pacman add-on for Firefox is a Pacman-clone and has the ascii look and feel of the old golden days. With good retro graphics, nice sound effects and a highscore list, this is one nice relaxer from your browsing routine.
Once installed, restart Firefox and get it from Tools > Pacman. Press either the UP or the DOWN arrow to start the game.
There are 4 different speed settings that work as difficulty levels: slow, normal, fast and insane.