The Light Blue I - Tetrimino used to clear 4 Lines at once. This special clear is called Tetris.
Performing a Tetris will send 4 Garbage Lines to your opponent.
If you can follow up the next clear to be another Tetris, you will get a Back-to-Back Bonus and send 6 more lines!
In the demonstration, you will notice a Back-to-Back Tetris but the total amount of lines sent is 11 instead of 10. The additional 1 sent line is due to a combo bonus.
What is a Back-to-Back Bonus?
Back to Bonuses are given when a Player performs 2 of the following line clears WITHOUT any other line clear being made between the two; Tetris, T-Spin Single, T-Spin Double, T-Spin Triple, or T-Spin Mini Single.
*The 2nd line clear will be rewarded with a Back-to-Back Bonus.
The benefits of this are substantial in sending Line Attacks as well as scoring in Marathon mode.