Mountainous Stacking

Mountainous Stacking is an opener that may result in a Perfect Clear chance after the T-Spin Triple in the second bag. It is founded by Agent RO in April 2021.

This opener has the same piece depenencies as Honey Cup. Like Honey Cup, you need an early I. Two differences between Honey Cup and Mountainous Stacking is that LS is placed with the L piece vertically and the J piece will be used in various orientations.

First Bag
In the first bag, it requires an early I. The J piece (L in the mirrored setup) is in Hold.

Second Bag and later
In the second bag, there are a few ways you can get a Perfect Clear, but there will be a lot of piece dependencies. If any of the 8 ideal cases is not applicable, the final case (compromise) is always available.


 * S → JO / S → O, J → I (98.85% PC rate)


 * O → I, S → JL / L → S (96.87% PC rate)


 * I → O, S → JL / LJ → S (95.91% PC rate)

If any of the eight cases cannot be applied, use the compromise below (44.80% PC rate).

Mountainous Stacking 2
Mountainous Stacking 2, by Agent RO, is the successor to Mountainous Stacking. Like its predecessor, it is mostly used as a Perfect Clear setup. However, unlike its predecessor, the latter has no piece dependencies (the mirrored setup is also accounted) and there are fewer case differentiations in the second bag. This opener is fully developed in early May 2021.

This opener has similarities with Gamushiro Stacking, like the 100% chance of stacking of this opener (including the mirrored setup) and high PC rates. However, unlike Gamushiro Stacking, there are better Perfect Clear rates here. Therefore, this is a good alternative to Gamushiro Stacking.

The L piece (J in the mirrored opener) is in Hold.

Second Bag and later
Choose one of the 3 ways depending on the order of the I, S and O pieces. In the third situation, one can make a Perfect Clear after 14 total lines.


 * O → SI (99.09% PC rate)

If you choose to forgo the Perfect Clear, you can use Mechanical TSD if you get an early J.


 * S → O (97.94% PC rate)


 * I → O → S: The third bag can always be stacked even with an early I piece, and fourth bag can always be stacked, leading to a Perfect Clear (99.72% PC rate).

Extra way

 * LI → S (96.90% PC rate): This is an extra way but for bags such as TIOLZSJ, this can be used instead of the third route.