Colors of tetrominoes

Pajitnov's original version for the Elektronika 60 computer used green brackets to represent blocks. Versions of Tetris on the original Game Boy and on most dedicated handheld games also use monochrome or grayscale graphics. But most popular versions use a separate color for each distinct shape. Prior to The Tetris Company's standardization in the early 2000s, those colors varied widely from implementation to implementation.

Scoring

The scoring formula for the majority of Tetris products is built on the idea that more difficult line clears should be awarded more points. For example, a single line clear in Tetris Zone is worth 100 points, while a back-to-back Tetris is worth 1,200.

Nearly all Tetris games allow 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 "hard drop". (Some games allow only soft drop or only hard drop; others have separate buttons.) Many games award a number of points based on the height the piece fell before locking.

In many games, an animation will complement scoring. For example, in the NES Tetris, Game Boy Tetris, and Game Boy Color Tetris DX, finishing some modes with at least a given score or a given difficulty results in a cut scene. In some cases, this is a rocket lifting off from a launch pad, where higher scores produce a larger rocket. Other possible cut scenes show dancers and musicians.

Gravity

Traditional versions of Tetris move the stacks of blocks down by a distance exactly equal to the height of the cleared rows below them. Contrary to the laws of gravity, blocks may be left floating above gaps. Implementing "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 additional lines, which may be awarded as more valuable clears.

Easy spin dispute

Although not the first Tetris game to feature "easy spin" (see The Next Tetris), also called "infinite spin" by critics, Tetris Worlds was the first game to fall under major criticisms for it. Easy spin refers to the ability of a tetromino's lockdown time to regenerate after left or right movement or rotation, and this has been implemented into The Tetris Company's official guideline. This new type of play differs from traditional Tetris because it takes away the pressure of higher level speed. Some reviewers even went so far as to say that this mechanism broke the game. The goal in Tetris Worlds, however, has to do with completing a certain number of lines as fast as possible, so technically the ability to hold off a piece's placement will not make achieving that goal any faster. Later, Gamespot would receive "easy spin" more openly, saying "though the infinite spin issue honestly really affects only a few of the single-player gameplay modes in Tetris DS, because any competitive mode requires you to lay down pieces as quickly as humanly possible." In response to the issue, Henk Rogers stated in an interview that infinite spin was part of the guideline, giving a rationale:

So the problem is you get part way through the game, make one small mistake, 'Aw man, I blew it,' and restart. I think that's an annoying way to play the game. So we decided it's better to give them a way to recover from that small mistake, but you're losing time. So if you sat there and rotated for, I don't know, five seconds, you've just taken five seconds out of the game that you needed to score so many points. So you won't find in the top games any gratuitous spinning going on, it just doesn't happen. It helps the beginning player who's trying to figure out what to do. It's a useless feature (for competitive play); it only helps if you're taking the time to think. The better players don't take that much time to think, that's the difference.

Source: Wikipedia