From Hard Drop Tetris Wiki
Hachispin (or HachiCannon) is an opener created by Hachispin. The setup consists of a TSpin Single followed by a TSpin Triple and Perfect clear.
First 2 bags
The setup needs an early O piece. A TSpin Single is made at the end of the first bag and a TSpin Triple at the end of the second bag.
Under circumstances, the second S piece needs to be softdropped. The second J, I and O pieces can be dropped in different ways. If possible, drop the second I piece 2 columns away from the wall because this gives a chance for a Perfect clear.



If the T piece from the first bag is rotated once, then these options for the second bag are available. The first one can result in a Perfect Clear.




Perfect Clear continuation
If the second I piece is dropped 2 columns away from the wall, then there is a high chance (69%) to make a Perfect clear (PC) at the end of the third bag (4 further cleared lines) whereas either the third I, L or J piece will stay on hold. The chance is especially high, if T piece comes first in third bag (94%), and also decent if either S, Z or O piece comes first (between 70% and 73%). The PC will always work, if S and T can be used to fill the bottom rows (see diagram 1). Same is true for T and J (see diagram 2). More precisely, the PC will always work, if T and either S or J are received as the first 3 pieces of the 3rd bag except for the starts JIT, IJT, JLT, LJT. It will also always work with TZO (no matter the order), but it will never work with ILJ (no matter the order). Diagram 2 shows the most common way to make a PC.
If the second I piece is dropped adjacent to the wall with the J piece above, then there is still a small chance (19%) to make a PC. Again, the chance is the highest if T comes first in third bag (40%). However, all PC opportunities are hard to spot. It is required to clear the third line before placing the S piece adjacent to the right wall.



If the second I piece is dropped adjacent to the wall but the second J piece is kept on hold until the TSpin Triple is made, then the chance to make a PC is increased to 74%. Note that this number is a little theoretical though because one can not see or think that many pieces in advance. The 11 most frequent PC opportunities are shown below. Note that the first 3 pictures are similar to the builds where one drops the I piece 2 columns away from the wall (same is true for the pictures in the bottom row). Also interestingly, all these 11 ways can be executed more often than the 4 ways shown above where they dropped the J piece horizontally adjacent to the left wall.











TSpin continuations
There are easy ways to make either a TSpin Double or TSpin Triple in the third bag. It is also possible to prepare an Imperial Cross or a Single Double (SD1).






Examples
pwn_by_numbers variation
If one gets an early L or J piece but no early O piece, then they can still try this variation. It is probably best to place the T piece vertically instead of upside down. With some luck they can fill the right corner with an S piece and make a TSpin Triple at the end of second bag.






Note that in this variation, it is harder to follow up with a TSpin Double (TSpin Triple is still easy). However, if one can stack the second bag like shown above, then there is a very high chance (83%) to make a Perfect clear (PC) at the end of third bag. The chance is especially high (95%), if Z piece comes first in second bag. The chances are also very high (between 88% and 89%), if they receive L or J piece first. The PC will always work, if Z and L can be used to fill the bottom rows (see diagram 2). The PC will also always work, if the third bag starts with Z and J piece (see diagrams 1 to 4). More precisely, the PC will always work, if Z and either L or J are received as the first 3 pieces of the third bag. It will also always work with TLJ (no matter the order). The first 2 pictures show the most common ways to make a PC.









Another way to make a TSpin Triple at the end of the second bag is shown below. The right corner is left empty, then covered by an O piece and eventually uncovered by the TSpin Triple line clear. L piece must stay on hold through second bag.






If one can stack the second bag like shown above (note that the second L piece has not been dropped yet), then there is a 96% chance to make a Perfect clear. Note that this number is very theoretical though because one can not see or think that many pieces in advance. The 11 most frequent PC opportunities are shown below; there are just too many ways to show them all.











Surrealist S
Surrealist S is similar to Hachispin, but the L and J pieces are placed in the opposite order, which results in different leftovers. A Perfect Clear after 14 lines is possible if one can stack the 1st to 4th bags like the below diagrams.









Here are some solutions. The first is the most common way and may result in a TSpin Double.





Alternatively, at the second bag, one may assemble like the diagram below which results in a TSpin Triple. However, there are not many continuations other than making a TSpin Double or Single Double.




See also
 Mr. TSpin's STD  an opener that also starts with a TSpin Single and a TSpin Triple
 Albatross Special  a similar looking opener where the location of S and Z pieces are swapped in first bag