Building a custom watch face on a $27 PineTime with Claude

Hacking with Claude on a $27 Smart Watch

Mike Kasberg used OpenCode with open-weight models—Kimi K3, K2.6, DeepSeek v4 Pro and Flash—to build a Casio-style watch face for the $27 PineTime. He started by getting a build working in the InfiniSim simulator, then fed the model a reference photo to replicate the layout. The first attempt was rough: text sizing and positioning were guessed, making elements overlap and unreadable. He switched to giving isolated, concrete feedback and fixed one text element at a time. Later he turned static parts into a fullscreen 240x240 background image so only dynamic elements needed code. It worked in the simulator, but on real hardware the image took 10 minutes to transfer over Bluetooth and screen refreshes lagged 1–2 seconds; the watch can't hold the whole image in memory and streams it from flash. He calls it a working prototype, pushed the code to GitHub, and had the model summarize lessons learned into an AGENTS.md file.

Why it matters: A first-person experiment with concrete debugging details, not a tutorial roundup or promo. H and K are solid, but the niche audience and lack of cross-source coverage keep R from hitting, so it lands right at the featured threshold.