Tetris Strategy

I’m going to bet that you’ve played or at least heard of the game Tetris. But have you ever tried to learn about the specific mechanics in Tetris? What about the game’s relation with graph theory? Well now you do, since you clicked into this article.

Let’s start with the basics of modern guideline Tetris (which is very different from the NES version, or the OG version of it). Here is a generic Tetris board, 10 x 20, and tiled into black and white grids. When we play Guideline Tetris, everything is within this board (with a few rare exceptions).

Now here are all 7 Tetris pieces, with dark and grey blocks marked out. I don’t know if you noticed, but the T-piece is slightly different from the other 6 pieces. In fact, it has an uneven number between dark and grey squares, while all other pieces are balanced.

So, what’s the significance? Well, these dark and grey squares construct what is known as “parity” in Tetris gameplay. Parity, in simple terms, is just the evenness between the number of black and white tiles in a player’s stack. To give an example, here’s two boards, one with even and one with uneven parity.

Before reading on, I challenge you to imagine how these two different stacks are created, and what difference there is.

This is uneven.

This is even.

OK, not sure if you found the difference, but the stack to the right would actually have to utilize a T-piece to make, while the stack to the left cannot be created with a T-piece. Taking

parity-wise, a T-piece would increase the difference between dark and grey squares by 2. However, if two T-pieces are placed together, the parity difference would be cancelled out, like shown on the right here.

Parity is something that no player would specifically pay attention to. However, as you play, you will develop a preference towards certain “terrains”, or shape of your stack. Here, what you like or dislike is often based on your mostly unconscious analysis of parity. Here is an example that would be tricky to deal with:

Here, we have limited placement options for our pieces. O, L, J piece placements have to involve the 8th column, and T-pieces have to be used to fix this unbalance in parity. But having a perfectly balanced board isn’t all sunshine and rainbows either.

For example, this stack would still be tricky to deal with. Imagine placing any piece but S, Z, and T on this stack without making it extremely ugly and difficult to manage. It’s important to keep a good parity balance as well as a preferable shape/ position of the stack.

Finally, there’s also a condition where unbalanced parity is actually preferred for optimal play. In modern guideline Tetris, there is a mechanism known as a “T-spin”, in which you clear a line after spinning a T-piece into place, giving you bonus points. Here’s a good video if you want to learn more about this specific mechanism. But we aren’t here to talk about T-spins today. Instead, let’s look at the shapes a T-spin would require to the right here:

This image is an example of a popular method to perform what’s called a “T-spin Double”, by dropping a T-piece in on its side and spinning it into place, clearing two lines at once. But note that around the hole designed for the T-piece, there’s an imbalance of parity. However, this is favorable as it provides additional points, and the parity will be evened out after the clear is made.

There’s still a lot to be covered on the topic of parity, like perfect clearing, four-widing, or skimming. But you can read that on your own if you are interested. Finally, I encourage you to test things out in game if you are skeptical! Theories can only get you that far, the rest is all practice. Have fun Tetrising!