Here are some common downstacking problems you will face in multiplayer.
There are no set pieces to follow, just click on the example and then click the quiz button a few times. You will get a random series of pieces each time you do this. Try to reach the bottom using as few pieces as possible.
Acceptable : Less than 30 pieces
Good : Less than 20 pieces
Uber: Less than 10 pieces
Problem1: Single line combo garbage (4Wide)
Your opponent just made a great 10 combo, Your field will look similar to this.
Problem2: 3Wide combo
Your opponent made a good 8 combo with singles and doubles. Your field will look similar to this
Problem3: Consecutive combo
Your opponent tried to combo but couldn't continue the chain. However, they made 2-3 small combos.
Problem4: Back to Back tetris/tspin
You attempted to build a tetris but your opponent sent you 2 tetrises back to back. You're at the top of the field and must downstack quickly. Stick pieces are scarce and you need to use some of the other pieces to downstack the long holes before another one arrives. For extra difficulty move your first I piece to the end of the sequence.
Bonus problem: If you can consistently finish the problems in under 20 pieces try building tetrises and tspins while downstacking.
Acceptable: 2 tspins / tetrises
Good : 5
Uber : 10