Ask yourself the following question: How many times, over the course of your life, have you bought a version of Tetris? Two? Five? A dozen? Tetris is about as ubiquitous a game as has ever existed. It singlehandedly defines an entire genre - when people are trying to describe an action-puzzler, they say, "You know, like Tetris." It has appeared on every conceivable system known to man. Type the word "Tetris" into Google and you will be playing any of a thousand free flash versions of the game inside of 3 minutes. Every single person who has ever touched a gaming system knows how to play Tetris, and has likely spent several hours doing so.