Tetris is widely known as the most popular computer puzzle game of all time. It was invented by Alexey Pazhitnov (last name transliterated Pajitnov by The Tetris Company) in 1985, while he was working for the Dorodnicyn Computing Centre of the Russian Academy of Sciences in Moscow, during the days of the Soviet Union. Pajitnov has cited pentominoes as a source of inspiration for the game. Its name is derived from the Greek numerical prefix "tetra-" meaning four, as all of the blocks are made up of four segments.

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, mobile phones, and PDAs. Tetris has even appeared as part of an art exhibition on the side of Brown University's 14-story Sciences Library. The game first gained mainstream exposure and popularity beginning in 1989 when Nintendo released Tetris on its Game Boy system. Tetris consistently appears on lists of the greatest video games of all time, and sales of the video game are second only to Super Mario Bros.

Seven randomly rendered tetrominoes (sometimes called "tetrads" in older versions) - shapes composed of four blocks each - fall down the playing field. The object of the game is to manipulate these tetrominoes with the aim of creating a horizontal line of blocks without gaps. When such a line is created, it disappears, and the blocks above (if any) fall. As the game progresses, the tetrominoes fall faster, and the game ends when the stack of Tetrominoes reaches the top of the playing field and no new tetrominoes are able to enter.

The seven rendered tetrominoes in Tetris are referred to as I, T, O, L, J, S, and Z. All are capable of single and double clears. I, L, and J are able to clear triples. Only the I tetromino has the capacity to clear four lines simultaneously, and this clear is referred to as a "tetris." (This may vary depending on the rotation and compensation rules of each specific Tetris implementation. For instance, in the Tetris Worlds type rules used in many recent implementations, certain rare situations allow T, S and Z to 'snap' into tight spots, clearing triples (T-Spins).)

Traditional versions of Tetris move the stacks of blocks down by a distance exactly equal to the height of the cleared rows below them. Unlike Newtonian gravity, blocks may be left floating above gaps. This behavior is known as "naïve gravity."

Some variants implement 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 additional lines, which may be awarded as more valuable clears.

Tetris has been embroiled in a large number of legal battles since its inception. In June 1985, Alexey Pajitnov created Tetris on an Electronica 60 while working for the Soviet Academy of Sciences at their Computer Center in Moscow with Dmitry Pavlovsky, and Vadim Gerasimov ported it to the IBM PC.

From there, the game exploded into popularity, and began spreading all around Moscow. This version is available on Vadim Gerasimov's web site.

The IBM PC version eventually made its way to Budapest, Hungary, where it was ported to various platforms and was "discovered" by a British software house named Andromeda. They attempted to contact Pajitnov to secure the rights for the PC version, but before the deal was firmly settled, they had already sold the rights to Spectrum Holobyte. After failing to settle the deal with Pajitnov, Andromeda attempted to license it from the Hungarian programmers instead.

Meanwhile, before any legal rights were settled, the Spectrum HoloByte IBM PC version of Tetris was released in the United States in 1986. The game's popularity was tremendous, and many players were instantly hooked—it was a software blockbuster.

The details of the licensing issues were uncertain by this point, but in 1987 Andromeda managed to obtain copyright licensing for the IBM PC version and any other home computer system.

For Amiga and Atari ST two different versions by Spectrum Holobyte and Mirrorsoft became available. The Mirrorsoft version did not feature any background graphics while the Holobyte version had a background picture related to Russian themes for each level. Games were sold as budget titles due to game's simplicity.

By 1988, the Soviet government began to market the rights to Tetris through an organization called Elektronorgtechnica, or "Elorg" for short. By this time Elorg had still seen no money from Andromeda, and yet Andromeda was licensing and sub-licensing rights that they themselves did not even have.

By 1989, half a dozen different companies claimed rights to create and distribute the Tetris software for home computers, game consoles, and handheld systems. Elorg, meanwhile, held that none of the companies were legally entitled to produce an arcade version, and signed those rights over to Atari Games, while it signed non-Japanese console and handheld rights over to Nintendo.

Tengen (the console software division of Atari Games), regardless, applied for copyright for their Tetris game for the Nintendo Entertainment System, loosely based on the arcade version, and proceeded to market and distribute it under the name TETЯIS (with faux Cyrillic typography incorporating the Cyrillic letter Ya), disregarding Nintendo's license from Elorg.

Nintendo contacted Atari Games claiming they had stolen rights to Tetris, whereupon Atari Games sued, believing they had the rights. After only a few (very popular) months on the shelf, the courts ruled that Nintendo had the rights to Tetris on home game systems, and Tengen's TETЯIS game was recalled, having sold about 50,000 copies.

Nintendo released their version of Tetris for both the Famicom and the Game Boy (the Game Boy version was developed by Bullet-Proof Software, Inc., who held the Japanese license, despite Nintendo's license to the game) and sold more than three million copies; some players considered Nintendo's NES version inferior because it lacked the side-by-side simultaneous play of Tengen's version, but Nintendo's Game Boy Tetris became arguably the most well-known version of Tetris. The lawsuits between Tengen and Nintendo over the Famicom/NES version carried on until 1993.

Pajitnov himself made very little money from the deal even though Nintendo was able to profit from the game handsomely.

In 1996 when Russian restrictions expired, he and Henk Rogers formed The Tetris Company LLC and Blue Planet Software in an effort to get royalties from the Tetris brand, with good success on game consoles but very little on the PC front. Tetris is a registered trademark of The Tetris Company LLC ("TTC"). TTC has licensed the Tetris mark to a number of companies, but courts have not decided on the legality of tetromino games that do not use the Tetris name. Blue Planet was later purchased by JAMDAT Mobile.

According to circulars available from the United States Library of Congress, a game cannot be copyrighted (only patented), which would invalidate much of TTC's copyright claim on the game, leaving the trademark on Tetris as TTC's most significant claim on any government-granted monopoly.

The Tetris Company's web site, Tetris.com, is a static page that says the "new website is coming soon!" with no outward links. Some players prefer Tetris brand games; others prefer homemade tetromino games downloaded from the Internet, which are given names such as "N-Blox" or "Lockjaw" so as not to infringe trademarks. In late 1997 and in mid-2006, The Tetris Company's legal counsel sent cease and desist letters to web sites that misused the Tetris trademark to refer to homemade tetromino games.

Some people refer to the pieces by the colour in which they are drawn in a particular implementation of the Tetris game, but those colours vary from implementation to implementation so this is not very sensible.

The scoring formula for the majority of implementations of Tetris is built on the belief that more difficult line clears should be awarded more points. In Nintendo's implementations on the NES, Game Boy, and SNES, the four possible line clears are as follows:

1. Single = (level+1)*40 one line is cleared.
2. Double = (level+1)*100 two lines are simultaneously cleared.
3. Triple = (level+1)*300 three lines are simultaneously cleared.
4. Tetris = (level+1)*1200 four lines are simultaneously cleared.

On most implementations, players may press a button to accelerate the current piece's descent, rather than waiting for it to fall. When a player locks a piece in this way, many such versions award a number of points based on the height the piece fell before locking. If a piece is manually dropped x lines and locked before the button is released, these versions will typically award either x points, or (level + 1)*x points. If a piece is not accelerated at all the player will gain no points for that piece unless a line is made.

Interestingly, according to the Twin Galaxies Intergalactic Scoreboard, the highest documented score on the arcade version of Tetris is 1,648,905 points achieved by Stephen Krogman of Boca Raton, Florida on Saturday, June 05, 1999.

In the arcade game, there are three events which contribute to your score: placing tetrominoes, clearing rows, and completing rounds.

The score for placing a tetromino depends on the height at which the piece lands, the level of a rainbow indicator next to the player's score, and whether the piece was dropped by accelerating it down. Let h be the height from the bottom of the play area to the block (0-20), let k be the number of bars shown on the rainbow indicator plus one (1-10), and let d be 1 if the piece fell at the normal rate or 2 if it was accelerated. The score for the piece is computed as d ( k² + hk ).

You get one bar on the rainbow indicator for every four lines cleared, up to the maximum height of 9 bars. The rainbow bars are cumulative between rounds, but you have to complete the round in order to keep the bars gained -- if you lose a round and choose to continue the game, you forfeit any bars gained during that round.

As you start the game you score a constant value of 1 for each piece you let fall or 2 for each piece accelerated downward. As you get further along and the pieces fall faster, you get a larger base score for each piece plus a bonus that increases the higher you build your puzzle. The down side to building up the puzzle, of course, is that it becomes increasingly difficult to clear lines.

The score for clearing lines is straightforward: 50 points for a single, 150 for a double, 400 for a triple, and 900 for a quadruple (a "tetris").

Upon clearing the required number of lines for a round, you are granted a bonus for the number of empty lines above the top of the puzzle. Let e be the number of empty lines (1-20). The bonus score for completing the round is computed as 5e² + 5e (ranging from 10-2100 points).

In addition, if you are playing a two-player game, the first player to complete the round gets an extra bonus of 2000 points.

Tetris has been subject to many changes throughout releases since the 1980s. It is difficult to place a standard on the game, as newer releases frequently progress it either to make the game better or to keep players interested. Newer Tetris games have made the trend of pace rather than endurance. Older releases such as Game Boy or NES Tetris offer 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. The next big Game Boy release after Tetris, Tetris DX, in marathon mode — comparable to mode A in previous releases — allowed an additional digit for the point meter. Even so, players still maxed it to 9,999,999 after hours of play. For The New Tetris, world record competitors have spent over 12 hours playing the same game. It is probably for this reason of seemingly everlasting play that in both Tetris DX and The New Tetris, the new modes sprint and ultra were added. These modes require the player to act under a timer — either to gain the most lines or points in that time. Recent releases like Tetris Worlds did away completely with point records. This particular game made records by how fast a certain number of lines could be cleared depending on the level. A drawback of this deviation, along with some other newer features, is that many traditional players rejected these advances all together. Critics of Tetris Worlds said it was broken due to how a piece is able to hover over the bottom for as long as a player needs; although, players of the game generally do not mind this feature because exploiting it will only hinder play, which is unfavorable to making a record time. Tetris LLC has been juggling different features with different modes of play in past years trying to satisfy traditional and newer players alike.

There are many different modes of play added in recent years. Modes appearing in more than one major release include: classic marathon (game A), sprint (otherwise game B or 40 lines), ultra, square, and cascade.

The field dimension of Tetris is perhaps the least deviated among releases, with the exception of some releases on handheld platforms with small screens. (For example, the Tetris Jr. keychain has 8 columns and 12 rows.) It is almost always 10 blocks wide by 20 blocks high. However, the original Tetris for Game Boy is a major exception with 10 by 18. The field height was probably decreased to fit within the Game Boy screen. As a result, Tetris for Game Boy was more difficult compared to its NES counterpart. Although, it is fair to add that Game Boy Tetris also is subject to faster speeds at lower levels.

Blocks spawn traditionally in center most columns horizontally at topmost and second topmost row. 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 especially older versions 5, 6, and 7).

In traditional games, a level-up would occur once every ten lines are cleared. During a level-up, the blocks fall slightly faster, and typically more points are given. In some newer games such as Tetris Worlds, the number of lines required vary upon each new level. The fall speed also varies but is usually no more than 20 milliseconds faster for each step per level. For example, NES Tetris operates at 60 frames per second. At level 0, a piece falls one step every 48 frames, and at level 19, a piece falls one step every 2 frames. This means for each level, pieces fall 16 milliseconds faster per step. Level increments will either terminate at a certain point (Game Boy Tetris will top off at level 20) or will increase forever yet not increase in speed after a certain point. NES Tetris will level up in until the speed of level 29 (due to frame restrictions, pieces are not capable of dropping faster than this), but tool-assisted emulation will show that the level indicator will increase indefinitely-- eventually glitching the meter so that it must use hex values. Modern games such as Tetris: the Grand Master or Tetris Worlds, at their highest levels, opt to drop a piece more than once per frame. Pieces will appear to reach the bottom as soon as they spawn. As a result, a hover or slide feature is often implemented into these games to help deal with an otherwise unplayable fall speed. In some games, the hover time is regenerated after a piece is moved or rotated.

Soft drops were first implemented in Nintendo releases of Tetris so that pieces would be able to drop faster while not lock as to slide into gaps. The other option is hard dropping, which is mainly featured in PC Tetris games such as Microsoft Tetris. Here, a piece falls and locks in one frame. Newer Tetris games 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 instantly but not lock.

Single rotation is an older restriction that has since been ruled out in nearly every new official release by the favor of dual rotation, which uses two buttons (one for clockwise and one for counter clockwise rotation). In traditional games, the unsymmetrical vertical orientation I-, Z-, and S-pieces will fill the same columns for each clockwise and counter clockwise rotation. Some games vary this by allowing two possible column orientations-- one for counter clockwise and one for clockwise rotations. Double rotation, only seen in progressive clones such as Quadra, rotates the piece twice.

Piece preview allows a look at the next spawn. This feature has been implemented since the earliest games, though in those early games, having the preview turned on made the score increase more slowly.

Newer versions of Tetris add different scoring goals not present in traditional Tetris. As achieving these goals while not topping out becomes more difficult, these games usually add a few features to help the player.

The New Tetris and The Next Tetris were the first official Tetris games to feature multiple piece previews, showing 3 in advance. Tetris Worlds for PCs and game consoles added 5 more, while the GBA version retained the 3 piece preview. Tetris DS uses the 6-piece preview.

The "phantom piece" is a feature that shows an obscuration in the shape of the current piece over where that piece would drop. The feature disposes with the old problem of misdrops and is relatively new.

Hold piece is an optional ability to reserve a piece for later use, allowing a player to either avoid undesirable pieces or save desirable ones, usually the I piece or a piece needed to complete another goal. Some clones featured it as a powerup that the player could earn and use once. A hold piece available to the player at all times was first featured in The New Tetris. Games that have hold piece generally activate it when the player presses both rotate buttons simultaneously or when the player presses a dedicated button, depending on the game. When hold piece is activated, it causes the falling piece to move to the top and trade places with the hold piece. However, 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. With initial rotation, when the player holds down the rotation button after the previous piece has locked down but before the next piece comes into the well, the next piece will come into the well in an already rotated state. Initial hold works similarly, as the piece will be already swapped with the hold piece when it enters the well. Initial rotation and Initial hold first appeared in the Tetris: The Grand Master series.

Tetris DS features wireless on-line play through the Nintendo Wi-Fi Connection system. This new version also 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. (This mode is themed on the NES video game Balloon Fight, hence the cage of balloons.)

Tetris DS also introduces the Metroid-themed "Catch Mode." In this mode, the pieces still fall downward, but the stack is moved and rotated instead. As the falling pieces bump against the stack, they gets clustered into it. To clear blocks, there must be a solid area of the stack that's 4x4 or larger. When this happens, the blocks glow and the music changes. After ten seconds or upon pressing the 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 offered different "puzzles" for selected rounds. The first three rounds are played normally, with no obstacles. At the start of round 4, eight bricks are placed vertically along each side of the well. Round 5 begins with ten bricks scattered throughout the bottom five 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 lines will randomly pop up underneath your 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.

A number of Tetris variants exist. Some feature alternate rules and pieces, and others have completely different gameplay. A large number of ports exist for different platforms. The most popular online client for Tetris is Tetris DS.

Normally, players lose for the following reasons:

* They can no longer keep up with the increasing speed, or

* A specific implementation of the game without very responsive control fails to keep up with itself when the pieces' downward velocity exceeds the maximum lateral velocity the player can apply to a tetromino. In other words, the possibilities for tetrominoes' movement are limited to the shape of a triangle in the game arena on faster levels. Some players may consider this situation a design flaw; however, it may be reasoned that this is an inherent challenge for the game. Altering this aspect, such as by assigning numerical placements, would change the dynamics of the game approach.

The question Would it be possible to play forever? was first encountered in a thesis by John Brzustowski in 1988 and more recently investigated in published articles by Walter Kosters, a player is inevitably doomed to lose.

The reason has to do with the S and Z tetrominoes. If a player receives a large sequence of S tetrominoes, the naïve gravity used by the standard game eventually forces the player to leave a hole in a corner.

Suppose that player then receives a large sequence of Z tetrominoes. Eventually, that player will be forced to leave a hole in the opposite corner without clearing the previous hole. Back and forth, the holes will necessarily stack to the top. Since the pieces are distributed randomly, this sequence will eventually occur. If played long enough, and the random number generator is theoretically perfect, any player will lose the game.

Practically, this may not occur. A good player may survive over 150 consecutive S and Z tetrominoes. On an implementation with a theoretically perfect random number generator (for example, based on hashing Brownian motion), the probability at any given time of the next 150 tetrominoes being only S and Z is one in (7/2)150 (approximately one in 4 × 1081). This number has the same order of magnitude as the number of atoms in the known universe. Most implementations use a pseudorandom number generator to generate the sequence of tetrominoes, and such an S–Z sequence is almost certainly not contained in the sequence produced by the 32-bit linear congruential generator in many implementations (which has roughly 4.2 × 109 states). In fact, newer Tetris brand games from 2001 and later tend to follow a new guideline such that the randomizer generates all seven tetrominoes in a permutation at one time, guaranteeing an even distribution over the short term.

Several of the subproblems of Tetris have been shown to be NP-complete on a playing field of size n.

* The theme tune used in the Game Boy edition of Tetris (Music A) has become very widely known, to the point that it is the theme song of level 20 of Tetris DS, even though that level is based on the NES version of Tetris. It is a Russian folk tune called "Korobeyniki" or "Korobeiniki."

* Music A in the NES version is "Dance Of The Sugar Plum Fairy," a tune noted to be scene 14c of act two of The Nutcracker, which was composed by Tchaikovsky.

* Music B in the Tengen version is the Kalinka, a famous Russian song written by Ivan Petrovich Larionov.

* Music C in the Game Boy version is an arrangement of Johann Sebastian Bach's Suite No. 3 In B Minor, BWV 814, IV. Menuett - Trio.

* Until the Sega Saturn, Tetris never (legally) appeared on a Sega system in the US. This led Sega to further expand the Columns series.

* Tetris JR was hinted at being the last Nintendo Game & Watch game but Nintendo canceled it, fearing that it would cannibalize Game Boy hardware sales. Years later a Tetris JR would appear as a keychain game.

* Tetris was referenced prominently in the video-game oriented cartoon Captain N: The Game Master.It was also referenced in The Simpsons episode "Strong Arms of the Ma".

* In the NES game Zoda's Revenge: StarTropics II, "tetrads" were featured heavily in the storyline as mystical stones the player was required to collect.

* In the European exclusive video game, Asterix & Obelix XXL, a certain part of a level requires the player to solve a Tetris-base puzzle to enter the next room.

* In Tetris (for Game Boy) and Tetris DS, the Two-Player mode features Mario and Luigi as the competitors.

* Also in the Game Boy Edition, when playing the A-Type Game, reaching 100,000 to 149,999 points will get you an animation of a small rocket lifting off. At 150,000 to 199,999 points, a slightly larger rocket will be rewarded. From 200,000 to 999,999 you will get the largest rocket from Mode A, which is a large Russian-styled rocket. When playing Mode B, completing the game at any of the level 9 stages rewards you with dancers and musicians. Completing level 9 with the height setting at 5 gets a large NASA-styled shuttle, which may be a reference to the abandoned Soviet Buran shuttle, which was later in development than the original US shuttle.

* A Tetris hybrid called Joy Joy Block appeared on the Neo-Geo arcade system in 1992. The rules of the game was similar to Tetris, only in order to win the game, a balloon had to be released into the air via the removal of blocks in the Tetris manner. A reference to this game appears in the video game Neo Geo Battle Coliseum, where a character named Ai has attacks that reference this game, including a move where the Tetris-like Joy Joy blocks fall from the sky.

* In Resident Evil 3, Jill Valentine must solve a puzzle involving lining up a series of Tetris-like shapes to form a corresponding pattern.Permission is granted to copy, distribute and/or modify this document under the terms of the GNU Free Documentation License, Version 1.2 or any later version published by the Free Software Foundation; with no Invariant Sections, with no Front-Cover Texts, and with no Back-Cover Texts.
Virtual Magic is a human knowledge database blog. Text Based On Information From Wikipedia, Under The GNU Free Documentation License. Copyright (c) 2007 Virtual Magic. Permission is granted to copy, distribute and/or modify this document under the terms of the GNU Free Documentation License, Version 1.1 or any later version published by the Free Software Foundation; with no Invariant Sections, no Front-Cover Texts and no Back-Cover Texts. A copy of the license is included in the section entitled "GNU Free Documentation License".

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