After attending a conference on roguelikes over the weekend, I was talking with friend Randy Lubin about how players move from learning rules to playing a game. We discovered/invented this really cool concept:

Game Mechanics Compression Ratio: the ratio between the initial instructions for a game once understood cognitively, and the complexity that they create during gameplay.

This is a computer science-oriented analogy to data compression. If we think of a zip file as the “compressed” version of the game, then this is the initial instructions. The full complexity of the game is the “uncompressed” version, what happens after you open the zip. The compression ratio is the size factor difference between the compressed and uncompressed version. Compression ratios can vary alot between different types of data.

When we were taking, I used the example of Quixote Games’ The Racket as a game that has a surprisingly large compression ratio. For a very basic set of instructions & items you start with, you end up with a game that is surprisingly complicated, especially in the case of social relationships it creates. And you can get going immediately.

Usually Go is used as an example of a surprisingly complex game, given the simple, “elegant” rules. However, this has a multi-stage decompression:
0. The fundamental rules
1. The implications of those rules
2. Playing a game.
You can’t really get to playing Go until you understand the implications of the fundamental rules, for example, the notion of “eyes”. Understanding these implication properly can take a long time and a few mock playthroughs, which makes its compression ratio lower. Again, we’re considering “compression ratio” to be a cognitive concept, rather than the amount of information that the literal description of the Go rules would require.

Nethack and other roguelikes are examples of a bad compression ratio. There’s so much stuff you have to learn, and so many mechanics included in the base game, that while you don’t need to understand all the mechanics to start playing, they’re still there, and you’ll have to come across them eventually, to really master it.