DT Cannon (DT砲)
DT Cannon is a very popular TSD → TST opener that is used when players have an early LS or JL. The second setup below is often used when you have an early JZ. It always works if you start with a J.
For the first bag, note how you can just hard drop L, S, and T without any rotations or movements from their spawn positions. This allows the player to build DT Cannon extremely fast. You can't do this if you mirror this setup, and it's one of the reasons why no one really uses the mirrored version of this opener.
Although not as widely used as the above two, you can also build DT Cannon with TZ as a base. This setup works whenever the first two setups don't work. However, players usually use different openers for piece sequences that do not allow them to build DT Cannon in the above two ways.
DT Cannon is a very versatile opener with many possible follow-ups:
There are many other ways to follow up with a perfect clear, but below is perhaps the easiest way to memorize:
After the 2 T spins, you are left with this shape which you will attempt to perfect clear:
If you want to have a higher chance of achieving a perfect clear, you can place your O on the right (second field below):
This way, you will have a 74.1% chance of achieving a perfect clear compared to a 36.1% chance when you place the O on the left. However, the advantage of placing the O on the left is that you can follow up with Amemiya Cannon when you can't achieve a perfect clear.
If you get a Z before an O, and if you get an O before a Z, respectively.
A C-Spin follow-up to DT Cannon.
The pieces are from the second bag, third bag, and Z from the 4th bag, respectively. On your third bag, you will need the Z to come early. The third variation is used when you have an early J, so the third bag is placed something like this:
It is possible to build a double TST by forgoing the first TST and building this C-Spin on top of the field instead. Typically you would complete the TST before following up with C-Spin. Here is an example of using this technique.
While this follow-up is risky to build since you are essentially not attacking for 2 or more bags, the double TST delivers a good spike to your opponent (14 lines).
A DT Cannon follow-up to DT Cannon. Although there are multiple ways to build this, below is probably the easiest way to build the second DT.
The pieces are from second bag, third bag, and fourth bag, respectively. You will need an early T and L for your third bag to do the TST and to slide your L in.
This follow-up is possible if you place the Z from the third bag upright like below:
A 4-Wide continuation to the opener which can be used when your opponent opens with the 4-Wide opener.
A Shachiku Train follow-up. Pay particular attention to the number of your upcoming S and Z pieces. You will need another S piece to build the overhang for the second TSD.
An Infinite TST follow-up. Often used in Ultra.
While DT Cannon is more often used as an opener, it can be a powerful mid-game technique if used appropriately. Assuming that you've been maintaining back-to-back, a DT Cannon will send 12 lines just like a Triple Double (TD). This is a higher amount than lines that a perfect clear would send (10 lines).
An easy way to think about building mid-game DT Cannons is to think of it as following these 3 steps:
Step 1. Spot a 2-height column
Step 2 and Step 3. Build the yellow part on the left. Build the orange part on the right.
These are common patterns used for the yellow part.
These are common patterns used for the orange part.
If you carefully look at each pattern that can be used for the yellow part, shown on the previous section again, and remove the top piece...
...they are TSDs. In other words, a lot of TSDs can be converted to DT Cannons. Turning a TSD into a DT Cannon is a safe and noncommittal way to build one mid-game.
Compare with Fractal:
The yellow and orange lines are what will be cleared once you complete DT Cannon. This means that you can have empty columns in column 1 and column 2.
Since you can have an empty column at column 1, you can create DT Cannon on top of that empty column:
Having an empty column at column 2 allows you to do another TSD after DT:
The lines cleared in the first T-Spin are marked yellow, and the lines cleared on the second T-Spin are marked orange. This means that you can delay filling some of the blocks for the TST (marked light blue on the second image).
Useful when timing your TSD to cancel incoming garbage lines as it is usually risky to accept lines when building a DT Cannon mid-game. Here's an example of doing so:
Some different variations.
3連TSD. A setup that looks similar to DT Cannon, but forms an STSD after the first TSD. As its japanese name implies, this setup yields 3 TSDs.
The only difference between this setup and DT Cannon is this 1 block marked purple below:
So you build it just like how you would create a DT Cannon. However there is one difference—since the setup forms an STSD after the first TSD, you can have blocks at these positions (marked green) below the structure:
This means that you can incorporate J/Ls into your base when building DT STSDs.
With all that in mind, here are some examples:
ダークネスカズスペシャル. Darkness Kazu Special. A setup with a TST on top of a DT Cannon. This setup is built similarly to how King Crimson is built—like how King Crimson is a setup with a TST on top of another setup (STSD). Often converted from a TSD, and it works best when you have already stacked up the right part.
DT砲2号. An alternate TSD → TST setup. It is rarely used in matches due to its relative complexity in setup. Built similarly to how Imperial Cross is built.
The easiest way to build it would be converting this particular STMB TSD into one. Some examples: