Tetris is a puzzle computer game, released on an extremely large spectrum of platforms. The game is available for
every video game console and computer operating system, as well as on devices such as graphing calculators, mobile
phones, portable media players, PDAs and it is composed from a sequence of tetrads (tetramineos) of four square
blocks each-fall down the playing field. These tetrads can be manipulated by moving each one sideways and rotating
it by 90 degree units, with the aim of creating a horizontal line of blocks without gaps. When such a line is
created, it disappears and the blocks above fall. As the game progresses, the tetrads fall faster and it ends when
the player "tops out", and when the stack of tetrominoes reaches the top of the playing field and no new tetraminoes
are able to enter.

Tetris game instructions mention the seven one-sided tetraminoes in tetris as I, J, L, O, S, T and Z -due to their
resembling letters of the alphabet-but players sometimes use other names for the pieces. All are capable of single
and double clears. I, J, and L are able to clear triples. Only the I tetromino has the capacity to clear four lines
at the same time and this is reffered to as a "tetris". The scoring formula is built on the idea that more difficult
line clears should be awarded more points. It allows the player to press a button to increase the speed of the
current piece's descent, rather than waiting for it to fall. If the player can stop the increased speed before the
piece reaches the floor by letting go of the button, this is a "soft drop"; otherwise, it is a "harddrop". If a
piece is manually dropped x lines and locked, it will award points proportional to the number of lines that the
player accelerated the piece. If a piece is not accelerated at all the player will gain no points for that piece
unless a line is made.

Some versions of Tetris implement "recursive gravity", a different algorithm that uses a flood fill to segment the
playfield into connected regions and then makes each region fall individually, in parallel, until it touches the
region at the bottom of the playfield. This opens up additional "chain-reaction" tactics involving blocks cascading
to fill addititonal lines.

Game Boy or NES Tetris provide records according to points. Since the meter for points is set to only a certain
number of digits, these game's records can be "maxed out" by an experienced player. On Game Boy the player must
rotate and stack tetriminos (blocks of varying shapes, each one made up of four squares) in such a way that the
blocks form complete horizontal lines. Once such a line is completed, the blocks vanish and all blocks above it
fall one line. The player accumulates points by placing pieces and succesfully clearing lines. A "Tetris" is scored
when the player clears four lines at the same time.

Tetris DX permits an additional digit for the point meter. Players still maxed it to 9.999.999 points after hours
of play. Tetris DX is a Game Boy Color game that is backwardly compatible with the original Game Boy. Tetris DX
features battery-saved high scores and three player profiles. DX has a new single-player mode, which is against the
CPU. DX features two new modes of play. In "Ultra Mode", players must accumulate as many points as possible within
a three-minute time period. In "40 Lines", players are timed on how quickly they can clear 40 lines of play.

In both Tetris DX and The New Tetris were added new modes sprint and ultra, that require the player to act under a
timer-either to gain the most lines or points in that time.

Tetris Worlds game kept records by how fast a certain number of lines could be cleared depending on the level.
There are many different modes of play that include: classic marathon (game A), sprint (otherwise game B or 40
lines), ultra, square and cascade.
It is almost always 10 blocks wide by 20 blocks high.

Game Boy is an exception with a 10 by 18 field of play. Tetris for Game Boy has an increased level of difficulty,
faster speeds at lower levels.

In traditional games, blocks spawn within the four most central columns and the two highest rows. The I tetromino
occupies columns 4, 5, 6 and 7, the O tetromino occupies columns 5 and 6, and the remaining 5 tetrominoes occupy
columns 4, 5 and 6 (or in some older versions 5, 6 and 7). In some recent games, pieces spawn above the visible
playfield. A level-up would occur once every ten lines are cleared and the blocks fall slightly faster and typically
more points are given.

In Nintendo releases of Tetris were first implemented soft drops so that pieces would be able to drop faster while
not lock as to slide into gaps. It also has the option hard dropping when a piece falls and locks in one frame.
Newer Tetris feature both options. Some games have their locking roles reversed, with soft dropping making the
pieces drop faster and locking down and hard dropping making the pieces drop instanlty but not lock.
The ability of rotating the pieces even if these touch the left or right walls, is also one of the features.
In the NES version if a Z piece is "vertically" aligned and falling touching the left wall, the player cannot
rotate the piece, giving the "bad feeling" that the "rotate buttons" are locked so the player has to move the piece
one position to the right and then rotate it to make the piece "horizontally aligned", losing then a precious time.
The piece preview feature permits a look at the next spawn and it has been implemented since the earliest games,
though in those early games, having the preview turned on made the score increase more slowly. The New Tetris and
The Next Tetris were the first official Tetris games to feature multiple piece previews, showing three in advance.

The New Tetris is notable for showing scenic fly-bys of famous structures (Sphinx, the Pantheon, saint Basil's
Cathedral, a Mayan temple). There are several key differences in gameplay from the original tetris. In addition to
clearing lines, one can also form 4x4 large squares of four pieces to form "blocks". When a block is created, it
turns solid gold or silver, depending on the makeup of the block- a block built from all the same kind of piece
becomes a golden block or "monosquare", while any other combination becomes a silver block or "multisquare". Blocks
can only be constructed from whole pieces: if any part of a piece has been cleared, then it cannot be used to form a
block. When a line that has pieces from a block is cleared, it earns more points.

The Next Tetris is a tetromino based puzzle video game released for the Playstation and is ine of the first uses 3D
Polygonal graphics in an official Tetris release. All the Tetris blocks rotate in 3D on the HUD while being stored
for future use. It also features a multiplayer mode with up to two players and an electronic dance music soundtrack

Tetris Worlds for PCs and game consoles added 5 more, while the GBA version retained the 3 piece preview. The player
can send their Mino Terinaut to six different worlds, where he/she plays the Tetris variant of that world. When the
player plays enough of that world, more Minos are rescued. The better the player does, the more Minos rescued. They
will then work to create the world into a home for Minos.

Tetris DS uses 6-piece preview. The "phantom piece" (reffered to in some versions the "ghost") is a feature that
shows an obscuration in the shape of the current piece over where that piece would drop. A hold piece available to
the player at all times was first featured in The New Tetris. When hold piece is activated, it causes the falling
piece to move to the top and trade places with the hold piece. The feature cannot be activated twice in a row; a
piece released from the hold must be dropped into the well. Initial rotation and initial hold are features that
make the game accept rotation/hold button inputs while the next piece is still in the preview area.

Tetris DS includes wireless on-line play through the Nintendo Wi-Fi Connection system that takes advantage of the
touch screen in the added "touch Mode", which has no time limit. Instead every block is already placed in a tall
tower and the player uses the stylus from the Nintendo DS to shift blocks left and right and in earlier towers,
rotate blocks. The goal is to clear enough lines so that a cage of balloons reaches the ground.

Tetris DS presents the Metroid-themed "Catch Mode" where the pieces still fall downward, but the stack is moved and
rotated instead. As the falling pieces bump against the stack, they get clustered into it. To clear blocks, there
must be a solid area of the stack that's 4x4 or larger. After 10 seconds or upon pressing X button, these blocks
disappear and shoot a laser beam in a plus-shape, the horizontal part equal to the number of rows cleared and the
vertical equal to the columns. This laser beam will destroy falling blocks and Metroid enemies in its path. The
parts of the stack not hit by the laser beam will be pulled in towards the center of the stack after the laser beam
dies. If a piece falls below of the bottom screen, the stack hits a falling block while rotating or the stack hits a
Metroid, the stack loses Energy. The player loses if the stack runs out of Energy or if the stack becomes so large
that it can no longer fit on the bottom screen.

The Tetris arcade game provides different "puzzles" for selected rounds. The first 3 rounds are played normally and
at the start of round 4, eight bricks are placed vertically along each side of the well. Round 5 begins with 10
bricks scattered throughout the bottom 5 rows. Round 6 begins with twenty bricks arranged in a pyramid. In rounds 7
through 9, the well starts out empty but single bricks will appear at random on top of your puzzle each time a
piece lands that does not clear any lines, potentially thwarting any advance planning you may have done. In rounds
10 through 12, incomplete "garbage" lines will randomly pop up undernaeth you puzzle, pushing the puzzle upward,
when a piece lands without clearing any lines. Rounds 13 through 15 begin with more blocks arranged in predetermined
patterns and the cycle continues throughout the remaining rounds in the game in groups of three.

Some variants of Tetris permit the player to choose to play with only S and Z terominoes and a good player can
survive well over 150 consecutive tetrominoes this way. Newer Tetris brand games tend to follow a new guideline
such that the randomizer permits the player to continue a game with a series of more than seven Z pieces.

Tetris Worlds permit the player to continuously rotate a block once it hits the bottom of the playfield, without it
locking into place. This allows a player to play for an infinite amount of time, though not necesarily to land an
infinite number of blocks.