20G

The term 20g refers to the block moving 20 units per frame, a.k.a instant drop. The behavior of this mode closely resembles if one were to hold up in Tetris the Grand Master 2.

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The block cannot move across other minos if the playing field is uneven. |

       Playing field

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         T moved right

Because of this, the best possible stack in 20g is a pyramid;

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Allowing the player to put his tetromino anywhere on the playing field.