Flat stacking is a passive approach to playing Tetris. As the name implies, the goal of flat stacking is to keep one's stack as flat as possible. This is primarily accomplished by keeping all of the pieces (except the O) in a horizontal orientation as much as possible.
General rules for flat stacking
- Try to lay all pieces in a horizontal orientation as long as the space permits you to do so.
- Only place a piece in a vertical orientation if a hole permits you to do so.
- Do not cover potential holes that will need to be filled later.
- Avoid making your stack TOO flat as seen here.
Why flat stack?
In theory, if you were extremely proficient at flat stacking, it would be very difficult for your opponent to KO you; they would have to be faster than you and be able to spike you.
If you flat stack well, not only do you keep your stack low, but you also have the chance of sending messy garbage to your opponent; this is a result from clearing small combos of singles and a few doubles.
You should only take a defensive position (flat stack) when you are near the top; if you flat stack near the bottom, you are simply wasting pieces.
Look at the first frame of each fumen diagram, and redraw the garbage on a separate fumen.
Using the pieces in order from top to bottom, arrange them to keep your stack as flat as possible. Click on the next frames to see the solutions to each problem. Note that there can be several solutions to a problem, as long as you meet the standard of keeping your stack as flat as possible. When given a problem with only three pieces, keep in mind that this is equivalent to looking at your current piece, your held piece, and your first preview. A four piece problem would mean that you are looking at two previews instead of one.
Bonus Problem - Hint: Think outside the box!