A "Tetris" occurs when 4 lines are cleared at once using an "I" piece. Tetris stacking is a technique that aims to maximise the number of Tetrises scored.
This page explains how to stack optimally for Tetrises.
| This piece... | can land on these surfaces... |
These shapes imply that the optimal stack surface must consist of both flat sections and shallow steps.
Stack pieces in the left 9 columns, and keep the rightmost column clear for an I-piece.
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Connect the "top surface" of the new piece horizontally with the "top surface" of the stack. This will create a flat surface rather than a bumpy surface.
| Flat surface created | Bumpy surface created |
Add shallow steps to your stack surface, with at least two flat cells at the base to provide placement options for O, S and Z pieces.
| Avoid the obvious choice | Rotate the "T" to create shallow steps... | |
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Avoid tall vertical surfaces by stacking the tall side against an outside wall.
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Or by burying a tall piece into a hole. |
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Try to keep space on both sides of a hole to provide placement options for both S and Z.
| Placement options for Z but not S | Placement options for S and Z | |
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If piece previews are available, it can be better in the long run to temporarily destabilise the stack.
| Without knowing the future... | This "J" placement is the best | |
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| But if you know an "L" is coming | You should do this... | |
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It is more important to connect a flat surface than to avoid a steep vertical surface.
| Flat surface created | Bumpy surface created |
It is more important to stabilise the stack than to score a TETRIS.
| "I" creates an option for Z | TETRIS leaves no options for Z |
This page did not discuss everything. To become a good Tetris player, you will also need to learn how to selectively cover holes when no ideal placement exists, and how to later uncover holes. I will write more about these in the future.
These guidelines were derived from a Tetris AI that I created to teach me more about optimal Tetris stacking. The AI will maintain a perfect Tetris stack for the following number of consecutive pieces on average:
| # of previews | # of consecutive pieces | |
| 0 | 153 | |
| 1 | 823 | |
| 2 | 9,458 | |
| 3 | 154,645 | |
| 4 | 1,783,670 |
Even with no previews or hold piece, the AI will on average maintain a perfect Tetris stack for 153 consecutive pieces before needing to switch strategies (e.g. using the hold piece, or temporarily covering a hole).