Kaidan Setups

The Kaidan, or Stairs, T-Spin setup, discovered by Tetris DS player TCM-WC, is a prophecy T-Spin Double method that takes advantage of a step formation beside an empty column. After an overhang is created, a Z tetromino is platformed over the empty column and used as a base for the T-Spin Double. After performing the T-Spin Double, the empty column should be open again. The Kaidan setup is especially effective in games that reward a Back-to-Back bonus. The Kaidan setup got its name because it is the Japanese word for stairs.

General Tips

 * Steps one to four are mandatory for the setup to work. The fourth step can often be incorporated through the tetromino used to create the overhang.

* Rows one and two do not have to be complete for the setup to function.

* The overhang and base are interchangeable in order of placement.

Filling the Bottom Gap
Although there are seven unique situations, they are uncommon during play and are generally less preferred than the line clear method.

Line Clearing the Edge
Line clearing is the most versatile method to prepare the Kaidan edge and is generally preferred and used more often than filling the gap. As opposed to the former, line clearing provides five unique situations, often encountered when skimming, with three where alternate tetrominoes may be used. It is important to note the three interchangeable situations (O-1 and S-1, J-1 and L-1, J-2 and L-2) as they provide for more flexibility.

There's actually another situation involving the Z tetromino which utlizes the alternative line clear Z base, but it's not recommended because the QTK alternative should be used instead.

Twist
T-Spin Single

Creating The Overhang
The overhang that is set up in advance in Kaidan setups are based on the principles of the T-Spin Double overhang.

Line Clear Base
This method is not recommended since the T-Spin Double can be directly created from the O tetromino. An alternative to using a Z tetromino would be to use a J. This is even less recommended, however, because the empty column will remain covered after performing the T-Spin Double.

T-Spin Double Replacements
Pre-Kaidan QTK Depending on the situation, a player may wish to opt for a QTK setup instead of setting up a premature Kaidan where the steps have not been made yet. In this example, rather than setting up the Kaidan overhang and then skimming down with an S tetromino before creating the base with a Z tetromino, the player can choose to create the QTK overhang and then clear with a Z tetromino to produce the T-Spin Double.

Imperial TSS / TSD TSS Depending on the situation, a player may wish to compromise by using an O tetromino to create a T-Spin Single instead of a Z tetromino to create a T-Spin Double. The option of using an Imperial TSS or a TSD TSS allows for versatility with different tetromino placements and when skimming up or down.

Transfers
Kaidan ST Arrow (Kaidan → ST Stacking)

Kaidan → Yoshihiro SD