How to build the DT cannon

The DT cannon is an opener that scores a T-spin double and then a T-spin triple: how to stack the first two bags and put both Ts in, one move at a time.

October 4, 2026

The DT cannon is an opener in which you stack the pieces of the first two bags into a fixed shape and score a T-spin double followed by a T-spin triple. The DT in the name stands for Double and Triple. The shape is almost the same every time, and in the first bag you place the pieces with hardly any rotation, which has made it the classic first opener for players who have just learned the T-spin.

The finished shape

The finished shape with the 13 pieces of two bags stacked. The third column from the left is open all the way down, and the T goes in here twice. The dotted outline is the first T (T-spin double).

The pieces used are all seven of the first bag, the six of the second bag other than the T, and two Ts (the T of the second bag and the T of the third).

Leave the third column from the left completely empty, from the floor to the top.
Above that column, the L of the second bag sticks out by just one cell. This is the overhang for the T-spins.
The T-spin double clears two rows and the T-spin triple that follows clears three, five rows in all.

The first bag: stack seven pieces

The L, S and T in the centre simply drop straight from where they appear. No rotation and no sideways movement.

Start with the centre. Hard drop the L, the S and the T in that order, without any other input. The L and the S form the base, and the T sits on top of them. A one-cell gap is left under the left arm of the T; this is where the T of the T-spin double will go later.

The first bag complete. The O goes at the left edge, the I upright immediately to the right of the T, and the J and the Z at the right edge. Nothing goes in the third column from the left.

The placing order follows these rules.

The centre goes L → S → T (because you stack from the bottom up).
The right edge goes J → Z (because the Z sits on top of the J).
The O and the I can be placed at any time.

The pieces will not always arrive in this order. When the order does not fit, use hold to put off just one piece. For example, if the S arrives before the L, hold the S, place the L, and then bring the S out. When even hold cannot make the order work (for example, the T comes first and the S also comes before the L), give up on the DT cannon and switch to flat stacking.

The second bag: stack six pieces and keep the T

The dotted outlines are the six pieces of the second bag. J upright at the left edge, L upright on the left arm of the T, Z on top of the T, O on top of the first bag’s Z, I upright at the right edge, and S at the very top.

J: stand it upright at the left edge, with the cell that sticks out at the top pointing right.
L: stand it upright on the left arm of the first bag’s T. The cell that sticks out at the top points left and hangs over the column you left empty.
Z: lay it flat on top of the first bag’s T.
O: place it on the right, on top of the first bag’s Z.
I: stand it upright at the right edge.
S: lay it flat on top of the O. Its top-right cell covers the top of the I, so place it after the I.

The T of the second bag is not placed; keep it. If the T arrives early, put it in hold and bring it out once the six pieces are stacked.

First shot: the T-spin double

The top of the empty column is blocked by the L, so the T cannot go in from directly above. You tuck it in from the top left with rotations.

Rotate the T clockwise so that it stands upright, move it all the way to the left wall, and soft drop it onto the J.
Rotate counter-clockwise once. The T lies flat and slides under the L’s overhang.
Rotate counter-clockwise once more. A wall kick drops the T into the empty column.
Keep soft dropping it to the bottom, then rotate counter-clockwise one last time. The T settles into the dotted position.
Hard drop to lock it. This is a T-spin double.

You press counter-clockwise three times in all. Until you are used to it, check where the T is after each press.

Second shot: the T-spin triple

The shape after the double has cleared two rows. This time the T goes into the same column and stays upright (dotted outline).

When the two rows clear, the L’s overhang comes down to exactly the height that the overhang for a triple needs. With the next T (the T of the third bag), use the same column once more. Pieces of the third bag that come before its T go in the six columns on the right; keep the four columns on the left open for the T.

As with the first shot, rotate the T clockwise so that it stands upright, move it all the way to the left wall and lower it.
Rotate counter-clockwise twice. The first rotation lays the T flat and tucks it under the overhang; the wall kick on the second drops it to the bottom of the column.
Hard drop to lock it. This is a T-spin triple.

Because the double and the triple come one after the other, the second shot also earns the back-to-back (B2B) bonus. How this column works is also explained in “The T-spin triple (TST): shape and entry”.

Afterwards

The surface left after the two T-spins. It is only two rows high.

After clearing five rows you are left with a low surface. From here, go back to flat stacking and aim for your next T-spin or Quad. There are many set ways to continue after a DT cannon, but for now make “landing both T-spins reliably” your goal.

Common mistakes

Placing something in the column that should stay empty

If even one block gets into the third column from the left, neither T will go in. Take care not to be one column off when you place the O at the left edge and when you stand the J at the left edge.

Placing the S before the I

The top-right cell of the second bag’s S covers the I’s column. If you place it first, the I can no longer get in, so keep the S waiting in hold until the I arrives.

Rotating the first T in mid-air

Rotate the T after it has landed on the J. If you rotate it in mid-air, it ends up on top of the L and does not enter the column.

In Setup Drills, “DT cannon” shows where each piece goes as a dotted target, one move at a time. The pieces come in random 7-bags just as in a real game, so you also practise putting off pieces with hold when the order does not fit. “Next move” tells you whether to place or hold each piece. Once you know the shape, try it with the dotted targets turned off.

Practice this