From Hard Drop - Tetris Wiki
Black Tea Cannon is an opener that starts with a T-Spin Double and usually results in a nice chance for a Perfect Clear after a further T-Spin Double. In the first bag it requires an early I piece as well as rather early O and L/J pieces. TKI 3 Opening variants are more frequently used for such first bags.
Perfect Clear after 6 lines
The second bag can be stacked in the following ways resulting in a T-Spin Double or T-Spin Single and giving a chance for a Perfect Clear after 6 lines cleared in total. If a piece is spit into 2 parts in a picture, it means that the piece must be inserted after the T-Spin line clear. Usually, the Perfect Clear is completed with an O or I piece coming first or second in the third bag. If a picure contains less than 7 pieces, it means that the missing piece can be kept on hold while filling the empty cells with the 2 first pieces of the third bag. Note that for the pictures in the fourth column, the I piece can be placed after Z with the help of a spin (doesn't work in the mirrored field though).
If the O piece shows up late in the first bag but L and I were already placed in the Black Tea Cannon-specific way, then the player may revert to the following setup. There's a very high chance that the second bag can be stacked like in the right-most picture below but the Perfect Clear chance is rather low: an O piece is always required among the first 2 pieces of the third bag.
Perfect Clear after 8 lines
If the I piece shows up early in the second bag, then said bag can be stacked in a way that clears a T-Spin Double and prepares a Perfect Clear after 8 cleared lines in total. As long as there's no incoming garbage, the Perfect Clear can be secured with proper stacking (requires 5 previews), no matter how the third bag looks like (100 % PC rate).
Note that with the help of SRS spins, the L piece can be placed after O, the Z piece can be placed after S, and the S piece can be placed after J and Z. So, with softdrop the continuation will always work, as long as I piece comes before O and T (66.67 % chance).
Another nice thing is that the resulting stack is symmetrical after 2 bag which makes it easier to memorize the Perfect Clear patterns. Instead of the patterns, we will list how the first pieces of the third bag must be placed in order to guarantee the PC with the remaining pieces of the third bag (one piece will always stay on hold).
By looking at the first 4 pieces, 3 of them can be selected and placed in one of the following ways in 86.9 % of all cases. The ways are sorted by one of the involved pieces.
By looking at the first 5 pieces of the third bag, 4 of them can be selected and placed in one of the aforementioned or following ways in 99.5 % of all cases, guaranteeing the Perfect Clear with the remaining pieces.
The remaining 0.5 % cases have the following form: S and Z don't show up in the first 5 pieces, O comes fourth and L or J comes fifth. In this case the player needs to know, if S or Z comes earlier and use one of the 4 following patterns accordingly:
Note that because the game was started with 2 horizontal T-Spin Doubles, each PC pattern will fulfill:
- If the T piece is placed, then the second row must be cleared with an odd number of empty cells in row #1 OR the third row must be cleared with an odd number of cells in row #4.
- If the T piece is placed vertically, then either L or J will not be placed (one of them will stay on hold). Since T is placed horizontally in each pattern listed above, both L and J must be used to achieve the PC.
If the I piece comes late in the second bag, then the player may try one of the following PC setups. None of them has a 100 % PC rate.