Fragile Game Design
I notice sometimes game designers define a mechanic as "fragile" – and I often catch myself doing this as well. I sat down for a little bit today and thought through what exactly that means. The definition I'm thinking about (and I would be happy for people to poke holes in this) is:
A mechanic is fragile when it is both convoluted and hard to repair.
When I'm talking about repair here, I mean in a conversation analysis sense. Players of analog games are constantly using repair techniques to assist each other and ensure the play they're doing reflects as closely as it can the formal mechanics of the game. If you accidentally move your piece five spaces instead of six, I can repair it by pointing that out and we can devise an adjustment.
An example of a hard-to-repair mechanic would be uncovering a hidden role in a board game. If I accidentally flip up the card revealing my hidden role halfway through the game, we can't rewind to an earlier state, we can't replace the role with a different role, and we can't pretend the other players don't possess this knowledge. The game state can't be repaired.
A mechanic may also be hard to repair if the other players can't help repair it. For example, if there's a special rule that only I am supposed to follow (and the other players don't know about) and I mess that rule up, the other players literally don't know and therefore can't help with repair.
Finally, a mechanic could be hard to repair if its outcome impacts many other mechanics. For example, if there's a formula for generating the acceleration of our spaceship in a racing game, and that acceleration is used to calculate velocity, speed, weapon firing, body endurance, etc. and we botch the calculation, it may be impossible to repair even if we realized it quickly – there are just too many other mechanics depending on its outcome.
There are many trivially fragile mechanics. For example, if each player is expected to do some private and complex math equations to determine the starting arrangement of their deck, it's likely they'll mess up the equation. It may take a while to notice, and the entire game is dependent on the results of said equation.
Fragility isn't fundamentally a bad thing in game design, but it does produce challenges for the game designer, especially when they've accidentally created a fragile system that doesn't appear fragile on the surface. Ultimately, games are played with humans, not machines – and we need to design around repair and conversational dynamics, not just optimal code.