## Interaction: The Key to Depth?

You’ve talked a lot about depth and complexity in regards to game design, but what about interaction between mechanics? How does it relate to depth and complexity? Any examples done well/poorly?

Alright, if game quality was purely tied to the number of states possible then the scale would not be linear. It would be exponential or logarithmic, like decibels. A strictly linear addition of states does not create a big jump in quality.

For a mechanic to significantly improve the game it must interact with the other mechanics, multiplying or exponentiating the number of possible states.

Interaction between mechanics creates context across time, allows variables to occupy a wider range of possible values and combinations of values, and ultimately is what creates depth.

It’s not enough to have a ton of mechanics if none of them interact with each other, or even synergy, which I consider to be a step below direct interaction.

Here’s a simple example. You have walking, and you have jumping in a totally blank 2d environment. Just a character and the floor. Imagine for a sec that you’re only allowed to jump when you’re totally still. So you have all these states for the positions which you can walk to, and maybe the velocities you can be in all of those positions, then you have like 30 or so states for all the positions you end up during your jump, rising and falling (imagine it takes 30 frames), multiplied by all the positions you can be in when you jump.

Now imagine that you are allowed to jump while moving, so this creates new states, where you have the combination of your X axis ground velocity and Y axis air velocity. This is direct interaction between mechanics, which creates additional states which the character can occupy. This game, which allows walking and jumping to be combined, has a broader possibility space, and also allows events in the past (walking) to affect events in the future (jumping after walking).

This is part of why I love the kick glitch in mirror’s edge so much, because it’s so flexible. It inherits a lot from your prior state and can create a large range of new states based on your input. It’s affected by how long you’ve been running on the wall, what angle you face into the wall, how fast you were moving beforehand, where you face when you jump. Through all of these there is a wide range of kick glitches you can perform. It’s possible to do one dropping down and landing on a platform far below, possible to do one that is long and straight, possible to do one out to the side, possible to do ones that gain more speed or less.

Combos in Smash Bros are also a great example of the interaction or synergy that mechanics can have. Low tier characters have poor synergy, high tier ones have amazing synergy.

A game full of contextual actions that exclusively do one thing would be a game where no mechanics have interaction. Or a 3d zelda game. They have a lot of really segregated mechanics in those.