Built on simple rules, Tetris established itself as one of the greatest video games ever made. By December 2011, it had sold 202 million copies—approximately 70 million physical units and 132 million paid mobile game downloads—making it one of the best-selling video game franchises. The Game Boy version is one of the best-selling games of all time, with more than 35 million copies sold. Tetris is available on over 65 platforms, setting a Guinness world record for the most ported video game. Tetris is rooted within popular culture and its popularity extends beyond the sphere of video games; imagery from the game has influenced architecture, music, and cosplay. The game also has been the subject of various research studies that have analyzed its theoretical complexity and have shown its effect on the human brain following a session, in particular the Tetris effect.