Combo

Combos 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.

Consecutive Line Clears

This type of combos is used in almost every official Tetris client that follows the Tetris Guideline. For every placed piece that clears at least one line, the combo counter is increased by +1. If a placed piece doesn't clear a line, the combo counter is reset to -1. That means 2 consecutive line clears result in a 1-combo, 3 consecutive line clears result in a 2-combo and so on. Each time the combo counter is increased beyond 0, the player receives a reward: In singleplayer modes, the reward is usually combo-counter*50 points. In multiplayer, the reward is usually some extra garbage lines sent over to the opponent. The table below lists the amount of garbage sent ("combo table") in some official clients:

Combo	T. Fr. +	T. Fr. e	TOJ/P	T. Bat.
0	0	0	0	0
1	0	0	0	1
2	1	1	1	1
3	1	1	1	2
4	1	1	2	2
5	2	3	2	3
6	2	3	3	3
7	3	4	3	4
8	3	4	4	4
9	4	4	4	4
10	4	4	4	4
11	4	4	5	4
12	5	5	5	4

Sum	30	34	34	36

legend:
	• T. Fr. + = Tetris Friends Expert Plus mode
	• T. Fr. e = Tetris Friends Normal and Expert modes
	• TOJ/P = Tetris Online Japan / Poland
	• T. Bat. = Tetris Battle on Facebook

Other clients use slight variations of the aforementioned procedure. In the Tetris The GrandMaster 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.

Time-based Combos

This type of combos is used in Cultris and Cultris II. A line clear starts the combo and each further line clear adds 1 to the combo counter and expands the available combo time as well. How much time is gained by a line clear depends on the current combo counter (less time for higher counters) and how many lines are cleared at once (more time for multi-line clears). A combo ends when the combo time expires. In Cultris II combo time can be also taken away, e.g. if a placed piece clears no line.

General strategy

Main Article: Combo Setups

By leaving 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.