DoubleYou

DoubleYou is an opener that starts with a T-Spin Single resulting in a W-shaped valley (thus the name). There are many ways to continue it, among others a C-Spin that can end in a Perfect Clear (pwn's STD).

Second Bag
Some ways of how a T-Spin Double might be stacked:

Some more advanced setups:

pwn's STD
The T-Spin Single can be also followed by a Triple Double Attack (C-Spin). This is also known as a Single Triple Double or short STD. This one was discovered by pwn_of_numbers:

This setup has 2 nice features. For one, twists can be used to stack the pieces in different orders.

Secondly, this setup can result in a Perfect Clear after 8 cleared lines in total. 72.6 % of all third bags can end in a Perfect Clear in theory. Each of the following 2 solutions will work for around 57 % of all third bags - sometimes after achieving a T-Spin Single or T-Spin Double.

If Z piece comes early in third bag, then chances are pretty slim for a Perfect Clear. In this case, you can also try to build a T-Spin Triple or Trinity instead of the T-Spin Double.

Here's another STD. It will work, if I piece comes before S piece in the second bag. Unfortunately, the fourth line cannot be completely filled with the second bag, and there's no opportunity for a Perfect Clear.