Mutating Mechanics

Chronicles of Rot: Part 2, a game design retrospective series

I have always struggled with scope creep. Planning a simple weekend one-shot inevitably devolves into me drafting the mythology of a forgotten pantheon. I get lost in the big ideas and the why of things. Ironically, I don’t even know the D&D gods for the settings I actually play in, except for the ones my own characters worship, and Lolth. (There is probably something to unpack there, but that’s for therapy, not Substack.)

Building Legacy of Filth under a strict one-page constraint might be the brutal cure I needed. It has been the best exercise I’ve ever done for learning how to cut scope.

Conceptually, my prototype rules felt lean enough. To survive the wasteland of rot, your fly had to track:

• 3 Core Stats

• 2 Resources: Health (hit points) and Stamina (action economy)

• A Victory Point Total

At the table, it was tedious.

I wrote a script to simulate the game, feeding over 250,000 digital maggots into the engine. I tweaked the stat balances and hazard rates until I achieved my desired 60% survival rate. I felt that you should win just a little more often. I discovered one truth at the bottom of a quarter million simulated corpses: Guts was always the optimal stat. It made sense when I stopped to think about it, because Guts dictates your hit points. Surviving just one more turn is often the difference between starting a lineage and becoming a smudge on the counter. My first instinct was to mathematically flatten this. Then I considered my belief that balance is a false god, and allowed that being born too stubborn to die should play like an asset.

So why when I started playing myself did I not like it? Why did it feel tedious? In retrospect Stamina was my biggest gripe. The only stakes tied to it was a roll for resting which you could choose to do anyway, and I honestly couldn’t remember if I had tracked it properly the previous turn. Instead of a desperate fight for survival, it felt like filing taxes. The game was hard, the tracking was fiddly, and even when a fly survived, I didn’t want to play again right away.

Players don’t experience and don’t care about your balanced simulation. They experience friction.

What works as intended over countless automated runs can still feel hollow to a human at the table. A perfect 60% win rate is mathematically unremarkable if the losses don't hurt and the victories don't feel earned. To make the game memorable, I couldn't just tweak Stamina to be "punchier." I needed something to make it matter every turn.

I decided that managing both Health and Stamina was miserable. So, I smashed them together into a single, unified resource: Anima.

With just that small tweak the game felt so much better. In consolidating the resources, the turn to turn decision mattered and you couldn’t forget to track it. You aren’t just spending action points anymore; you are burning your fly’s literal lifeforce to survive.

The Legacy Breakthrough

Even with Anima fixing the turn-to-turn friction, the core challenge was still incredibly punishing. I stepped back and asked myself what I actually love about RPGs. Two things stood out:

1. The Shadowdark Arc: I love discovering who a character becomes over time.

2. The D&D 5E Crunch: I have a complicated love/hate relationship with build optimizing around damage per round.

That got me thinking: What if this fly game had a legacy loop where each generation keeps it’s mutation and gets just a little bit stronger?

Instead of every run being a flat reset, successes would carry genetic weight. If you survive long enough to pass on your genes, the next generation inherits the benefits. Over multiple runs, the game shifts from brutal, desperate survival into a feeling of earned mastery. You start min-maxing a housefly.

The interesting part is how the simplification of Anima and the legacy progression worked together. Simpler turns made each choice clearer, and persistent genetic growth made each victory matter more.

At this point, Legacy of Filth started to feel like maybe a real game system. Although, I now had a physical problem: I was trying to cram a multi-generational, genetic nightmare RPG onto a single tri-fold pamphlet. In the third design post of Chronicles of Rot, I’ll share lessons learned while commissioning art, the hidden design trap of telling players “you can build anything,” and why fixing the game’s onboarding ultimately forced me to take the scope lessons learned and apply them immediately to my one-page darling and cleave it in two.