Adding a 17-stage promotion exam system to my hanafuda game in one session

I shipped Shin KoiKoi v0.1.0 two days ago — a free, polished hanafuda Koi-Koi card game built solo with Godot 4.6 .NET in 2 days. (Earlier post: the v0.1.0 release log ) For v0.1.1 I added a 17-stage promotion exam system that turns the existing rank progression from "MMO experience grind" into something closer to the real Japanese kyū/dan exam tradition. Here's how I designed and shipped it in one Claude pair-programming session. The problem with auto-promotion The v0.1.0 rank system was a flat