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.

The Tetris shapes

This piece... can land on these surfaces...

These shapes imply that the optimal stack surface must consist of both flat sections and shallow steps.

Guidelines for Tetris stacking

Stack pieces in the left 9 columns, and keep the rightmost column clear for an I-piece. →→→ 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... →→→ →→→ Avoid tall vertical surfaces by stacking the tall side against an outside wall. →→→ →→→ Or by burying a tall piece into a hole. →→→ 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 →→→ 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 →→→ But if you know an "L" is coming You should do this... →→→

Dilemmas

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

More...

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.

About this tutorial

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).