How to Tetris

22: DT Cannon 2

Tutorial Videos

The first few seconds may render in low quality. Please give them a few seconds to render.

The Basics

DT Cannon 2 is a variant of the original DT Cannon. It gives a T-spin double followed by a T-spin triple:

Diagram Set 22-1
12
3
The first T-spin double is horizontal.

Dirty DT Cannon 2s should not be taken if possible:

Diagram Set 22-2
This DT Cannon 2 is dirty. After the 2 T-spin line clears, the top red-circled blocks will block the bottom red-circled hole. The green-circled part is also empty, meaning you cannot connect your pieces and downstack combo as you downstack to protect yourself by blocking garbage.

However, its firepower sometimes makes up for it. Hence, the player may sometimes make deliberately dirty DT Cannon 2s.

Common Mid-Game Chances

Mid-game DT Cannon 2s are difficult to create because they often require a very jagged field. However, there are some ways where this does not happen.

1. Easiest DT Cannon 2 Chance: Sky Props

    Upgrading a Sky Prop to a DT Cannon 2 is the most straightforward construction method in a relatively smooth field:

    Diagram Set 22-3
    12
    Spot a mid-game Sky Prop chance like this.  Simply upgrade it to DT Cannon 2 by adding a few pieces!

    2. General Ways

    Here are ways to construct the DT Cannon 2’s base (the left side):

    Diagram Set 22-4
    AB
    CD

    And here are ways to construct the tall side (the right side and overhang):

    Diagram Set 22-5
    AB
    CD

    These are the most common piece combinations to make parts of the DT Cannon 2. Please memorize them.

    3. Imbalanced Parity Situations

    It is difficult to spot DT Cannon 2s mid-game because they often require severe parity issues (jaggedness) first. There are a few ways to construct it.

    The first, below, involves spotting a jagged stair-like field with parity imbalances. Instead of putting a T piece to immediately resolve parity, you proactively make a Sky Prop. As shown in an earlier sub-section, this can then be easily upgraded into a DT Cannon 2:

    Diagram Set 22-6
    12
    Starting field with a stair-like situation with severe parity imbalances.The player uses a horizontal S to proactively make a Sky Prop or T-spin suspension.
    3
    Instead of a regular Sky Prop, he builds the lavender areas to make a DT Cannon 2.

    You can also upgrade a T-spin triple into a DT Cannon 2:

    Diagram Set 22-7
    12
    Starting field with a regular T-spin triple opportunity.The player instead puts S and Z horizontally like this.
    3
    He then upstacks the lavender blocks to make a DT Cannon 2, upgrading it from a regular T-spin triple.

    The above method is often dangerous because of the jaggedness of the construction.

    From my experience, DT Cannon 2 cannot be forced. It is far harder to create it mid-game than the original DT Cannon 1. This is because the shape of DT Cannon 2 entails a severe parity imbalance that makes its appearance mid-game rare. I sometimes try to force DT Cannon 2 for fun — but they mostly fail.

    4. Freestyle DT Cannon 2

    You must sometimes freestyle DT Cannon 2. There are few fixed, memorizable methods for this. Freestyle and experiment!

    Diagram Set 22-8
    12
    An example of a freestyled DT Cannon 2.

    Advanced

    DT Cannon 2 has advanced variants.

    1. Magic Key DT Cannon 2

      You can insert a Magic Key into DT Cannon 2s:

      Diagram Set 22-9
      12
      Spot a Sky Prop with a J (L if mirrored) piece.Putting the Z like this makes the top layer a Magic Key.
      34
      Make the first T-spin double.Make an overhang. Then, you will get a DT Cannon 2.

      This is dangerous, and I cannot recommend it, except for pure fun.

      2. DT Cannon 2 C-Spin

      DT Cannon 2s can end with a C-spin. This makes the last T-spin a T-spin double instead of a usual T-spin triple, making it clean:

      Diagram Set 22-10
      12
      Spot a T-spin triple chance (pink blocks) and an extra hole (red circle).Upstack the top parts. The resulting DT Cannon 2 has an extra T-spin double.

      The resultant field, after the final T-spin double line clear, will be clean, exposing the next garbage hole. These kinds of DT Cannon 2s are the safest and cleanest.

      3. Spliced DT Cannon 2

      You can insert T-spin triples into DT Cannon 2s:

      Diagram Set 22-11
      12
      Recognize this shape.You only have to stack L and S this way.

      This inserts a T-spin triple to strengthen the DT Cannon 2, making it more powerful. However, it is risky and should only be used mainly for fun.

      In a Nutshell

      DT Cannons 2 are difficult to use mid-game because of their parity imbalance requirements. However, some very high-level players like Firestorm and Furea have used them mid-game successfully. I can create them easily, thanks to my experience.

      Pros and Cons
      ProsPowerful T-spin double to T-spin triple provides significant burst.

      As powerful as a typical DT Cannon.

      Has some very easy-to-spot mid-game chances from Sky Props.
      ConsRare to construct because it needs an uneven parity situation.

      Dirty as it ends with a T-spin triple.