Puzzle game in which geometric shapes called fall down onto a playing field, and the player has to arrange them to form gapless lines

Block puzzle is primarily composed of a field of play in which pieces of different geometric forms, called "tetrominoes", descend from the top of the field.[2] During this descent, the player can move the pieces laterally and rotate them until they touch the bottom of the field or land on a piece that had been placed before it. The player can neither slow down the falling pieces nor stop them, but can accelerate them, in most versions. The objective of the game is to use the pieces to create as many complete horizontal lines of blocks as possible. When a line is completed, it disappears, and the blocks placed above fall one rank. Completing lines grants points, and accumulating a certain number of points or cleared lines moves the player up a level, which increases the number of points granted per completed line

In most versions, the speed of the falling pieces increases with each level, leaving the player with less time to think about the placement. The player can clear multiple lines at once, which can earn bonus points in some versions

If the player cannot make the blocks disappear quickly enough, the field will start to fill; when the pieces reach the top of the field and prevent the arrival of additional pieces, the game ends.[3] At the end of each game, the player receives a score based on the number of lines that have been completed.[4]: 16  The game never ends with the player's victory. The player can complete only as many lines as possible, before an inevitable loss.[2]

Since 1996, the Block Puzzle Company has internally defined specifications and guidelines to which publishers must adhere to be granted a license to Tetris. The contents of these guidelines establish elements such as the correspondence of buttons and actions, the size of the field of play, and the system of rotation.