A pleasantly detailed analysis of how the various editions of Tetris chose what piece was next.

In 1985, Alexey Pajitnov and Vadim Gerasimov released Tetris to the public. This fun and highly addictive game challenged players to fit pieces together that were dealt in a random order.

Since then, over 150 licensed versions of Tetris games have been released. Varying in game modes, rules, and implementations, they all play slightly—or very—differently.

In Tetris, a randomizer is a function which returns a randomly chosen piece. Over the years, the rules of how pieces are chosen has evolved, affecting gameplay and actual randomness.

Several of them have been reversed engineered and documented. I’ve curated a list of ones that I believed to be important and show how the state of Tetris has changed over the years. —Simon Laroche