Sega rotation
From Sega Retro
Sega rotation is a set of rules for Tetris, divised by Sega during development of their eponymous Sega System 16 arcade release of the game. While the concept of Tetris was designed by Alexey Pajitnov and the rights of the game then held by the Russian state-owned Elektronorgtechnica (Elorg), the specifics of the game were, at the time, not standardised, meaning every company which created a Tetris game implemented the rules in a slightly different way.
"Sega rotation" is not an official term, but was adopted by the Tetris community to differentiate the system from other Tetris rulesets, most notably "Nintendo rotation" which was implemented in the Nintendo Entertainment System and Game Boy releases of the game. For a while, Sega rotation became the de facto standard for the game across Japan, being used as a base for several Japanese-produced Tetris games during the 1990s (e.g. Tetris Plus by Jaleco, and the Tetris: The Grand Master series by Akira).
The current owners of the Tetris property, The Tetris Company created a standardised "super rotation" ruleset some years later, of which most developers now follow.
Rules
Core elements of Tetris (i.e. tetromino pieces fall, lines are cleared) are consistent across all licensed variants of the game - the rotation systems merely dictate how the blocks should rotate.
Sega rotation pre-dates the concept of "wall kicks", meaning if there is no space to rotate, the piece will not rotate. Later variants of the game will shift the block left or right if there is not enough space to perform a rotation (and there is space for the piece to be moved), meaning Sega's system is more restrictive than what would come later. The "ceiling" also acts as a blockade, meaning it is not possible to rotate any tetromino until they have fallen one row down.
The extra time given for players to rotate blocks just before the piece is considered to have landed is equal to the time it takes for a piece to fall one block down. That is to say, when tetrominoes are falling slowly, there is more time to rotate than at higher speeds.
The game ends when a tetromino cannot be spawned without intersecting a block (as opposed to any block reaching the top row of the screen).
Tetrominoes
"I" block
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"O" block
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"J" block
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"L" block
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"S" block
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"Z" block
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"T" block
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Starting positions
Games which implement Sega rotation
System 16
- Tetris (1988)
- Flash Point (1989)
- Bloxeed (1989)
System E
- Tetris (1988)
Mega Drive
- Tetris (1989)
- Flash Point (unreleased)
System 18
- Bloxeed (1989)
System C
- Bloxeed (1989)
Saturn
- Tetris Plus (with small differences)
NAOMI
- Sega Tetris (1999)
Dreamcast
- Sega Tetris (2000)
References
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Basic rotation
Tetrominoes start out centered, rounding to the left. I goes in columns 3–6 counting from the left, O in columns 4–5, and others in columns 4–6. Each tetromino starts with its topmost solid block in row 20 (or 22 in TGM ACE). Each tetromino is ordinarily spawned flat side up. There is no initial rotation, and no wallkicks. Additionally, the ceiling blocks rotation.
Apart from I and O, all tetrominoes rotate such that the bottom of the tetromino is at the bottom of the piece's bounding box. S and Z rotate between two states so that the center column stays constant. O does not rotate; I rotates between two states as depicted in the illustration.
The differences between Sega rotation and Nintendo Rotation System are that the flat-side-down states of J, L, and T are pushed down by one space, that S and Z round in different directions, that I rounds differently from the other pieces, and that I requires more space under it to rotate to a vertical orientation.
Sega rotation originally used no wall kicks. Arika took Sega rotation, added mild wall kicks and initial rotation, and ended up with TGM Rotation, or Arika Rotation System. In addition to the TGM series, most arcade games developed in Japan before the guideline followed the Sega rotation rules with varying degrees of wall kicks, such as Flash Point, Bloxeed, Sega Tetris, and the Tetris Plus series.