How to Tetris

24: BT Cannon

Tutorial Videos

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The Basics

Diagram Set 24-1

BT Cannon is a popular Korean method that involves a T-spin double followed by a T-spin triple.

Carry it out this way:

Diagram Set 24-2
12
Starting field.Make the first T-spin double.
34
You get a T-spin triple.Complete the T-spin triple.

While there are many mid-game opportunities for it, I suggest giving it up if the T-spin triple overhang is very unclean, such as in the situation in the diagram below:

Diagram Set 24-3
This BT Cannon is unclean because the blocks in the top red circle block the garbage hole in the bottom red circle.

Common Mid-Game Chances

BT Cannons have an extremely complex shape that has many piece and field dependencies, making its creation during the mid-game challenging. However, here are common ways to build it mid-game.

1. General Ways

    Here are common mid-game situations and patterns to memorize and build parts of the BT Cannon. You can easily build the lavender areas over the 2 lines of garbage:

    Diagram Set 24-4
    AB
    CD
    EF
    GH
    IJ
    KL

    2. Jagged Pattern

    When you get a jagged pattern mid-game, often from overlapping garbage holes, you can easily make a mid-game BT Cannon:

    Diagram Set 24-5
    1
    Starting field.
    Alt. AAlt. B
    This choice shows a C-spin constructed out of step 1.This other choice shows a BT Cannon constructed from step 1. You put the S on the left side, mirroring the Z in Alt. A.

    This makes remembering easier since the C-spin in Alt. A and the BT Cannon in Alt. B share the same mid-game opportunity from step 1’s zigzag pattern.

    3. Partly Completed Base

    This situation happens when the base is only partly present:

    Diagram Set 24-6
    12
    In step 2, the player creates a base using a horizontal J placement.
    34
    He then constructs the “tall side” of the BT Cannon.He concludes with the overhang, finishing the BT Cannon.

    4. Parapet Upgrade

    The easiest way to make the BT Cannon is by upgrading it from a Parapet:

    Diagram Set 24-7
    12
    You make a Parapet with the S and J pieces.
    3
    You then upgrade it to a BT Cannon with additional pieces.

    5. Creation from Nothing

    This situation involves making everything from scratch:

    Diagram Set 24-8
    1
    Starting field.
    Alt. AAlt. B
    Suggested way to make a BT Cannon.Another method.

    6. Hyper Jagged Situation

    This situation involves seeing the hyper-zigzag pattern, typically arising from overlapping and focused dirty garbage. This happens more often than one thinks:

    Diagram Set 24-9
    12
    Starting field with a hyper-jagged situation.One can easily make a BT Cannon with the Z and L pieces like this, followed by an overhang.
    34
    The first T-spin double concludes.This leaves a C-spin.

    This BT Cannon above shares the same mid-game starting situation as a C-spin. Note the S’s placement:

    Diagram Set 24-10
    12
    Same starting field as the last diagram set.One can easily make a C-spin instead.

    Compare it to Cut-Copy, which can be built from the same mid-game opportunity:

    Diagram Set 24-11
    12
    Same starting field as the last diagram set.One can easily make a Cut-Copy like this.

    Since BT Cannon shares the same opportunity as a Cut-Copy above, you can quickly memorize how to construct the former.

    Advanced

    BT Cannons have advanced variants.

    1. Non-Linear Construction

      You can construct BT Cannons in an out-of-order manner, which gives you slightly more chances to create it mid-game:

      Diagram Set 24-12
      12
      First, make this from a Parapet chance, like in the earlier examples.You slot in the Z piece with a soft drop to make the BT cannon.

      2. Spliced BT Cannon

      You can insert T-spins into a BT Cannon:

      Diagram Set 24-13
      A
      A spliced BT cannon: you insert a T-spin within the BT cannon.

      This method is called Tarantula.

      Spliced BT Cannons are advanced and impractical techniques. They are often used only for fun or to wow viewers during a Twitch or YouTube Tetris stream.

      In a Nutshell

      BT Cannons are, honestly, a gimmick, but they have rare, niche situations, like clustered, overlapping garbage patterns, where they are practical if you can carry them out fast enough. They are more often used as openers by Korean players.

      Pros and Cons
      ProsPowerful burst with an innate T-spin triple.

      It is good to upgrade from some situations like a Parapet.

      Often the most practical situation in jagged, overlapping, and focused garbage hole situations.
      ConsThe BT Cannon’s substructures are often messy and difficult to manage.

      The BT Cannon setup is challenging to recognize, even for advanced players.

      It ends in a T-spin triple, which can be dirty.

      Needs a lot of stacking to create.