I wrote down every mistake from 3 years of building my Compose Multiplatform app. All 224 of them.

Hey all — I'm maxrave-dev.

Three years ago I started SimpMusic — a FOSS music client in Kotlin and Compose Multiplatform — because the app I wanted didn't exist and I figured I could learn by building it.

Today it runs on Android, Windows, macOS and Linux, and it's sitting at almost 11k stars with real users on F-Droid and GitHub releases. I'm saying that not to flex: I'm 23, for most of those three years I had no senior to ask and nobody reviewing my code, and I learned almost everything the hard way — Media3 internals, Room migrations at real-user scale, Glance widgets, a native media engine bound over JNA, desktop packaging and code-signing. There's plenty in the codebase I'm still not proud of. Some bugs cost me whole days. A couple are honestly embarrassing.

But I kept notes. Every time something burned me — a Media3 quirk, a migration gone wrong, a Compose trap — it went into my personal notes: messy, half-finished, scattered all over the repo.

Recently I turned those hand-written notes into something more useful: a skills pack for coding agents. 224 short markdown docs in the agent-skills format, so Claude Code / Cursor / Codex can pull the right doc exactly when you hit the same problem (`npx skills add maxrave-dev/kotlin-footguns`) — but it's all plain markdown, and it reads fine as a human reference too.

To be clear, this isn't an AI dump with my name on it. Every doc follows one structure — what breaks, the mechanism behind it, and commands you can run to check whether your own codebase has the same problem — and every claim was verified against the real tree before shipping. The notes and the scars are mine; the agents just helped me make three years of mess consistent.

https://github.com/maxrave-dev/kotlin-footguns

GPL, plain markdown, free. I'm sure some docs still have mistakes — I'm still learning. If you spot one, tell me. That's the whole spirit of the thing.

https://preview.redd.it/q6arenvezcmh1.png?width=1796&format=png&auto=webp&s=6c07244a2f5cfddd22eaf1bca42e870d83d863c8

submitted by /u/maxrave-dev
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