In 1985, while trying to recreate a favorite puzzle game from his childhood called pentominoes, Pajitnov quickly realized that although he was able to successfully create it, there was a problem. It was boring. Once the player figured it out, the game ended too quickly and with no incentive to replay it. So instead, Pajitnov imagined a different type of game consisting of a descent of random pieces that the player would turn to fill rows. Pajitnov felt that the game would be needlessly complicated with twelve different shape variations, so he scaled the concept down to four-block shapes of which there are seven variants. He called these 7 unique pieces tetrominoes.

But now there was a another problem. Once the pieces fell and the rows were filled, the game would end too early, even though it was much more engageing with the falling tetrominoes pieces. His next modification is the key to Tetris. Once a player filled one line, it disappeared. This not only gives the player a sense of achievement, but allows the game to keep going. And with that, the addictive puzzle game sensation of Tetris was born.