The translation was automized by my Prolog program, which generates semantically equivalent JavaScript code for each 6502 instruction and applies some optimization techniques to the generated program (e.g., removal of redundant flag calculations). The outcome is an exact simulation of the original arcade game. The graphics interface and the emulation of the Centipede video hardware were directly coded in JavaScript and rely on HTML5 and the Canvas element. So you should have a quite recent browser version supporting these features to be able to play the game.