Timmie's Tetris Tips: Height Differentials and I/L/J plans

In celebration of this year's "Carnival of Death" (celebrating "Death Mode" in Tetris the Grand Master) I thought I'd offer some general Tetris stacking tips that might be useful to think about for newer players.  I'll try to make these agnostic of rotation system, so they should apply across both ARS and SRS games!

A key component of good Tetris stacking is to place pieces in a way such that your stack is receptive to as large a variety of future piece placements as possible.  Generally this means you want to try to make your stack "flat, but not extremely flat".



Here's an example of a very stable and receptive stack:

Notice how there are multiple placement options for each of the 7 tetromino shapes (L, J, O, I, T, S, Z).



Now here's an example of the opposite:

In this situation our stack is extremely jagged and we have no immediately good placements in the main stack for Z, S, and T pieces, and instead would be forced to drop them in the hole on the right side, hoping for L, J and I pieces to fix the rest of our stack.



One of the keys to maintaining a stable stack is to look at the height differentials you create with each placement, and particularly the exact height of the "wells" you create.

For example, in this situation, your attention should immediately jump to the well created in column 2.  This well is 3 rows deep, which means it can only be filled with an I piece (unless you make a hole).  We also lose access to column 1 while waiting for this I piece since nothing can be placed there without also affecting column 2.

Well that are 3 or more rows deep are BAD because they can only be filled with 1 out of the 7 possible pieces.  This means two things:
- Try to avoid creating wells of 3 or more rows.  The J piece here could have been placed elsewhere, like in columns 8+9 pointing upwards.

And perhaps even more importantly:
- If you DO create a well of height 3 or more, try to fill it with your next I piece ASAP.

This is very important.  In general, if you have a situation where you absolutely need a given piece, make sure you don't waste your next instance of that piece on something else!  This is a problem I see all the time with inexperienced players -- don't let it happen to you!  When you have a well 3 rows deep, you should form a PLAN for the next I piece -- an "I plan".  Keep remembering this so that the next time you receive an I block, you immediately place it in the needed place.



Just like we have "I plans", another very useful concept to think about are "L plans" and "J plans".  I, L, and J are often the most common pieces for which you will have a specific need for. (closely followed by T)

In this situation, we have a well that is 2 rows deep on the very left in column 1.  This well can only be filled by two pieces: a J or an I.  But since the I piece is so powerful (a bit less so in ARS, but still powerful), and can be used to make Tetrises, it's generally much preferred to use a J to fill this well.  This is also because using an I maintains a height difference of 2 (more on this later).  So whenever we see this formation on the left side of the screen, we should form a "J plan".

Again, this is a common mistake.  Often beginners might place a J in columns 6-8 instead.  Do not do this!  Fill the slot on the left side with your J instead!



Let's look at one more example to close things out:

Imagine that we place the O piece here (as shown in the shadow).  What should spring to your mind?
That's right!  We've created a slot that can only be filled by L or I.  And of the two, it's much preferred to fill it with L!

Notice that if we fill this slot in column 5 with I, the height differential between columns 4 and 5 is still 2 rows.  This is another reason why using L and J to fill 2-deep slots is usually preferred -- because L and J will end up with a height differential of 0 instead of 2, which often results in a smoother stack.

So we should aim to fill this hole with an L if at all possible -- we should form an "L plan".  If we end up getting an I before an L, that's ok too (use your judgment), but L is preferred.



But wait...was there a better way to handle this situation?

Placing the O piece here instead is much better.  Why?  Because it keeps the ability of both L and J to fill the well, not just L.  In fact, the very next piece is a J here!  In this situation, I still have an "I/J/L plan" vaguely in mind because again, these are the only 3 pieces that can solve this well.  If I get a T or Z or S, i may not intuitively know exactly what to do with it.  But if I get a L or J in the next few pieces I should know exactly where to place it as long as this structure exists.

This O placement demonstrates that thinking about flexibility for these sorts of wells is important.  A lot of this comes down to experience with specific structures and situations.  In the next installment of these tips I'd like to go over some common ones that are good to know about.