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Tetris is a video game invented by Alexey Pajitnov whilst he was working for the Academy of Sciences in Moscow, inspired by a pentominoes game he had purchased earlier.
When a line of blocks has no gaps, it is complete and disappears.
The maximum number of lines that can be completed simultaneously is 4, since at least one block is required per line. This can only be achieved with the "I" tetromino: doing this is known as a "tetris".
In order to master the game, the technique of sliding a piece just before it sets is invaluable, as well as using both rotation buttons, when available.
A massively popular game, Tetris or a clone thereof has appeared on nearly every games machine available, it has even appeared as part of an art exhibition on the side of a building [1]. Its most popular port has been to the Game Boy, considered by some the one true form of the game.
When a row of blocks is cleared and removed, the stacks of blocks above it fall. Many versions of Tetris simply move blocks down by a distance exactly equal to the height of the cleared rows below them. This results in behavior unlike real-world gravity, in that blocks may be left "floating in mid-air". Many feel that this behavior contributes to the gameplay rather than detracting from it.
Newer games may 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 falling to fill additional lines, which those games tend to reward with a higher score.
An example implementation of Tetris-like game which simulates normal gravity is Gravytris, written with OpenGL.
Normally, players lose because:
But what if the speed did not increase? Would it be possible to play forever?
An article has been published that addresses this issue, and it turns out that in theory, you are doomed to lose eventually.
The problem is the S- and Z-shaped pieces. Suppose you got a large sequence of S-shaped pieces of the same orientation. Eventually, many implementations' approximation of gravity (see above) forces the player to leave a hole in a corner.
Suppose you then get a large sequence of identical Z-shaped pieces. Eventually, you'll be forced to leave a hole in the opposite corner, without clearing your previous hole. Now, things go back to the original orientation for a while and so on until the pieces stack up to the top. Since the pieces are distributed randomly, this sequence will, eventually, occur. So, if you play long enough, and your random number generator is theoretically perfect, you will lose the game. (See also a more detailed discussion of this issue at http://www.geom.umn.edu/java/tetris/explanation.html, along with an implementation written in Java that has been modified to deal only S- and Z-shaped pieces.)
Practically, this does not occur because the pseudorandom number generator in most implementations, which is usually a linear congruential generatorLinear congruential generators (LCGs represent one of the oldest and best-known pseudorandom number generator algorithms. The theory behind them is easy to understand, and they are easily implemented and fast. It is, however, well known that the propertie, does not deal such a sequence.
Even on an implementation with a theoretically perfect random number generator (for example, based on hashing Brownian motionThere are two meanings of the term Brownian motion the physical phenomenon that minute particles immersed in a fluid will experience a random movement, and one of the mathematical models used to describe it. The mathematical model can also be used to desc) and with naïve gravity, a good player can survive over 150 consecutive pieces that are all S-shaped or Z-shaped; the probability at any given time of the next 150 pieces being only S- and Z-shaped pieces equals 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.[2]
Several of the subproblems of Tetris have been shown to be NP-completeIn complexity theory, the NP-complete problems are the most difficult problems in NP, in the sense that they are the ones most likely not to be in P. The reason is that if you could find a way to solve an NP-complete problem quickly, then you could use th.
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