If you have never experiences Tetris before you can play it here for free. WARNING: You will waste many hours doing this.

According to the very trusted WikiPedia: Tetris is a puzzle video game originally designed and programmed by Alexey Pazhitnov. It was created on June 6, 1984,  while he was working for the Dorodnicyn Computing Centre of the Academy of Science of the USSR in Moscow. He derived its name from the Greek numerical prefix "tetra- (all of the game's pieces, known as Tetrominoes, contain four segments) and tennis, Pazhitnov's favorite sport.