Chirality in Game Design

Chriality is a term you probably learned in chemistry class and I learned in Walter White’s chemistry class. No shame in being aware of the roots of our knowledge. Point is, chirality is a term we use to refer to a type of symmetry – where a thing can be constructed with all the pieces relating to one another in the ‘same’ way but the whole object is meaningfully different because they can’t be superimposed.

The simple way to think of it is that chirality is the handedness of the object. Your left hand and right hand (if you got one of each) are structurally ‘the same’ with thumbs and fingers all relatin to one another in roughly the same way and distances, but the construction means that no matter how you try, you cannot rotate the pair so that they are both representing the same position.

Chirality is very important in chemistry, where two chemicals can be identically composed and yet have wildly different effects. Now you know a word you might not have known before. If a thing has this property, this ‘handedness,’ then it’s chiral, and if it can’t be constructed to have a handedness, then it’s known as being achiral.

Here, let’s look at an example. Here, let’s look at the classic Tetris pieces, from the Citizen Kane of videogames, Tetris. There are seven of these, which is the maximum number of shapes you can get from four blocks, constructed with their specific rules.

In Tetris you can only rotate the pieces on one plane, and only at 90 degrees at a time. The 90 degrees isn’t a problem for chirality, but the way you can only rotate the tiles means you’re presented with seven pieces:

Of these seven pieces, three of them are achiral, so let’s drop them out.

These four pieces are the chiral pieces. In the rules of Tetris, when you spin them around these pieces are going to never be able to represent their obvious twin. A big part of the skill in Tetris is recognising, very quickly, the places that pieces can’t go, and that means not getting tricked by these pieces and building with a plan going forward.

Thing is, when you’re not building a computer game and you’re making game with physical pieces of cardboard and whatnot, you encounter this:

Because if you can just flip over those pieces and suddenly, the chirality disappears. Which means that if you want to play with this kind of tile structure and these kinds of rules, you need to make sure that your pieces have a clear back, otherwise players are going to intuitively pick them up and flip them over and then where are you.

This can be something you play with intentionally, too! Some puzzles are deliberately made with pieces that have ambiguous facing, to make them more difficult. When you let pieces flip, you might be giving people twice as many possibilities to work out, and increasing complexity of your game, or you might be giving people fewer options and making choices simpler.

If you’re working in small press spaces, of course, this can be really important – you might only have the budget with your game to cut say, five pieces, and you need all the pieces represented, then you can use the fact that some pieces are achiral if flippable as part of the game rules.

Our game pieces have materiality, it’s worth thinking about it, and thinking about the intention behind how you represent them. There may even be rules you didn’t realise you were respecting because they seemed obvious to you (like, ‘no flipping pieces’).

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