I had never written code for the DS, and I built it with Claude Code. I wrote the specs, the design and the balancing, and Claude wrote most of the C. The post goes through how that worked, and through the technical parts I found the most fun:
- a 2048x2048 world that is never stored: terrain is computed from (x, y), only the player's changes are kept in a hash table - night done by changing the 256-color palette instead of redrawing the screen - power grids and pipes computed per network with union-find (there is a small step-by-step animation in the post) - trains with schedules, block signals and pathfinding, plus redstone-like logic gates - a headless Mac build of the game with a text interface, so AI agents could play ~470 test sessions and even help balance the game
You can download the ROM (English and French) and play it on a flashcart or in melonDS.