What is TETRIS?

Tetris, arguably the world’s favorite and most addictive video game, was developed in Moscow in 1985 on a computer dubbed the Soviet Electronica-60. Later that year, its creator, Alexey Pazhitnov, adapted it for players worldwide on the IBM PC platform. From then on, it has soared to great success, selling over 30 million copies on Nintendo's Game Boy system alone.

Figure 1. The seven "tetrads" that are used in Tetris, each comprised of four squares.

Shapes called tetrads fall, one at a time, from the top of the playing field (Figure 2) to the bottom. Tetrads are comprised of 4 squares arranged into 7 different patterns, shown above in Figure 1. The object of the game is to keep the blocks from piling up to the top of the playing field. To do this, the player must move and rotate the tetrads as they fall, attempting to fit them together. If the player can completely fill one horizontal line with colored squares, that line disappears and any filled squares above move down. If the player is unable to fill lines completely, the tetrads will stack up and eventually reach the top of the playing field. The game ends when a new tetrad that is placed at the top of the playing field is unable to drop at all due to the filled blocks.

To help the skilled player plan better moves, the next tetrad to fall is typically shown somewhere on the screen. Which tetrad appears next is determined by a random number generator. The game counts of the total number of lines completed. The game starts at Level 1, and the level is incremented after every 10 lines are completed. (After completing 90 lines, the game remains at level 10.) With each increase in level comes an increase in the speed of the dropping tetrads. Points are assigned when lines are completed, with bonus points for completing several lines simultaneously (shown in the chart below).		Figure 2. The Tetris playing field, shown during game play. The falling tetrad can be rotated and dropped along the left side to complete 4 lines simultaneously – also known as "getting a Tetris."
LINES COMPLETED	SCORE
1 line 2 lines simultaneously 3 lines simultaneously 4 lines simultaneously	10 points * level 30 points * level 60 points * level 100 points * level