Imperial Cross (インペリアルクロス)

A TSD → TSD setup. The only difference for the shape itself compared to Fractal is the shifted overhang:

However, the lines cleared are very different for the two TSDs. The lines cleared in the first TSD is marked yellow, and the lines cleared in the second TSD is marked orange:

ダブルダガー

A TSD → TSD setup that is also known as "double dagger" in the Japanese community.

Imperial Cross is also slower to execute compared to Fractal. It is not uncommon to rotate five times for the first TSD.

Building Imperial Cross

Conversion from a TSD is the most common and the most recommended way to build an Imperial Cross. It is a popular follow up to the flat top TKI opener.

Below is another example of building an Imperial Cross. It is one of the lesser common ways to make one. Assuming that you have the same field as shown in the first picture, a TST (third image) could be a better choice depending on your piece queue.

Notice that the only difference between the shape of a TST and the shape of an Imperial Cross is the block marked purple:

Using Imperial Cross

Fixing Bad Overhangs

Imperial Cross can be used to fix bad TSD overhangs. Note that you can achieve the same effect with a Triple Double, which sends more attack (third image below). Therefore Imperial Cross is often built as an alternative when you can't make a TD to fix the bad overhang because you don't have the necessary pieces.

Imperial Cross shifting your open column underneath can be useful for fixing bad overhangs, as shown above. However, this property can make it an inappropriate choice for specific fields, even if you're tempted to make one because you have the right pieces.

In certain situations, you could fix the bad overhang created by an imperial cross by building another imperial cross or a TD.

credit to kazu for the example

Lines Cleared

Other than the shifted overhang, another difference between Imperial Cross and Fractal is the lines cleared for the first and second TSD. The lines cleared for the first TSD are lower (marked yellow) for Imperial Cross.

Because of this property, the orange line can be filled later after the first TSD. This is in contrast to Fractal where you need to have a complete setup before attempting any TSDs:

Imperial Cross is therefore often used when you can't build a Fractal due to piece constraints.

C-Spin

When you build Imperial Cross with a flat overhang like the ones above, you can clear the bottom two lines instead, in order to follow up with a C-Spin.

Example:

credit to kazu for the example

TD

A TST → TSD setup often used mid-game

FOUR