Combo

Combos (known as REN mainly in Japanese games) are bonuses that exist in certain games which reward multiple line clears in quick succession. The exact conditions for triggering combos, and the amount of importance assigned to them, vary from game to game.

Combo system (consecutive line clears)

This system is used in several Tetris games, particularly those based on the Tetris Guideline. The combo counter starts at -1. For each placed piece that clears at least one line, the combo counter increases by 1; if a placed piece does not clear a line (also known as a combo break), the counter resets back to -1. For example, two consecutive line clears equals a 1-combo. When the combo counter increases beyond 0, the player receives a reward, depending on the mode.
For single-player modes, the standard scoring formula for combos is 50 points × combo count × current level.
For multiplayer modes with traditional Battle mechanics, combos add extra garbage lines being sent to the opponent. The following table lists the amount of extra garbage sent in official Tetris games:

Combo	Guideline Standard (Tetris Online (Japan) onwards)	Tetris Friends	Tetris Friends (Expert Plus)	Tetris Battle (Facebook)	Tetris 99	Puyo Puyo Tetris 2	Tetris Effect: Connected	Tetris Effect: Connected (ZONE enabled)
0	0	0	0	0	0	0	0	0
1	0	0	0	1	1	0	0	0
2	1	1	1	1	1	1	1	1
3	1	1	1	2	2	1	1	1
4	2	1	1	2	2	2	2	2
5	2	3	2	3	3	2	2	2
6	3	3	2	3	3	3	2	2
7	3	4	3	4	4	3	3	2
8	4	4	3	4	4	4	3	2
9	4	4	4	4	4	4	3	2
10	4	4	4	4	5	4	3	3
11	5	4	4	4	5	4	3	3
12	5	5	5	4	5	4	3	3
13+	5	5	5	4	5	5	4	3
Sum	39	39	35	40	44	37	30	26

Other games use slight variations of the aforementioned procedure. In the Grand Master series, the increment of the combo counter depends on how many lines are cleared at once and the combo counter is used to calculate a score multiplier for the corresponding line clear.

General strategy

By leaving at least two columns open, one can clear combos easily. However, an I tetromino cannot clear a line in this case, so the Hold box should contain a non I piece, if the game allows, or the bottom of the funnel should be 1 cell wide.

Combo number 1 (with T in hold)

You can help illustrate this combo by adding a piece.

Combo number 2 (with slot for I)

You can help illustrate this combo by adding a piece.

Various skimming methods can end up in combos.

Official Tetris Games with Combos in Rules

• Magical Tetris Challenge
• Tetris The Grand Master
• Tetris The Absolute The Grand Master 2
• Tetris The Grand Master 3 Terror-Instinct
• Tetris Zone and subsequent post-2007 Guideline-based Tetris games (Tetris Splash, Tetris Party, Tetris Effect, etc.; notable exceptions include Tetris (PlayStation Portable) and Tetris (PlayStation 3))