Tetris is a video puzzle game originally designed and programmed by Alexey Pajitnov in June 1985, while 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-", as all of the pieces contain four segments, and tennis, Pajitnov's favorite sport.

  
The game (or one of its many variants) is available for nearly every video game console and computer operating system, as well as on devices such as graphing calculators, oscilloscopes, mobile phones, portable media players, and PDAs.

It has even been played on the sides of various buildings, with the record holder for the world's largest fully functional game of Tetris being an effort by Dutch students in 1995 that lit up all 15 floors of the Electrical Eng'g department at Delft University of Technology.

According to research from Dr. Richard Haier, et al. prolonged Tetris activity can also lead to more efficient brain activity during play. When first playing Tetris, brain function and activity increases, along with greater cerebral energy consumption, measured by glucose metabolic rate. As Tetris players become more proficient, their brains show a reduced consumption of glucose, indicating more efficient brain activity for this task.