I built a walking game with Claude, designed to make you put your phone away.

I've been building The Hidden Realm , a free-to-play UK location-based walking game inspired by Britain's landscapes, history and folklore. The slightly ironic part is that a lot of the development involved AI, but the game itself is deliberately designed to encourage people to spend less time looking at a screen. I'm a solo developer and started the project in May. Claude has been a significant part of the process, particularly through agentic conversations where I describe what I want the Realm to do, work through the design and systems, and then iterate on the implementation. Nothing had write access to anything. Every change went in by hand, one at a time, tested before the next. It's grown into considerably more than I expected: A native Android walking app with GPS tracking and server-side anti-cheat A web-based game hub Supabase/Postgres backend with server-side gameplay validation Three competing Wards contesting territory 40+ folklore-inspired creatures, influenced by biome, weather and time of day, some anchored to real-world locations A lore system that grows around where players actually walk Privacy built into the design, including automatic deletion of route data The creature artwork is AI-assisted, and turned into 3D models players can examine in the game. I'd commission an artist if I could afford one. I can't, and the alternative was not building it. But the core experience is deliberately simple: Start a walk. Put your phone in your pocket. Go. Walk with friends. Talk. Enjoy the scenery. Explore somewhere you've never been. When you finish, that's when the game reveals what happened. Recently the 100th Beacon was placed, which unlocked the next chapter of the Book of Forgetting. Along with 500 player encounters of the Bell Tower Wisp creature. That's been one of those moments where something I designed on a screen has started becoming a world shaped by actual players. The hardest part of the whole project, though, wasn't any of the code. The game attaches real local history to real places, so the content has to be true. Confident, well-written, entirely plausible history is exactly what these models are best at producing, and it's indistinguishable from the real thing until you go and check. A concrete example. A fragment about a shopping centre built on a former isolation hospital included the detail that it treated American and Canadian airmen during the wars. It reads well. It fits. The site did treat servicemen, and that part is documented, but the airmen detail had no source I could find anywhere. So the rule I ended up with: history is verified against real sources or it doesn't ship. Anything I can't confirm is either dropped or moved into a category explicitly labelled as fiction, so nobody mistakes it for fact. Nothing goes in unread. That discipline has been more work than the database schema, and it's the only reason I'd defend the content at all. The project is now live on Google Play in the UK, with players walking it in different parts of the country. There's something quite satisfying about using AI to help build a game whose purpose is ultimately to encourage people to look up from their screens. Real-world testing caught something I hadn't thought about. If you want to pause the walk to duck indoors or stop for lunch, you have to take the phone out, which breaks the entire point. So there's now a Wear OS companion app shipping soon that handles pause, resume and stop from the wrist. The phone stays where it is. thehiddenrealm.co.uk I'd be interested in hearing from other Claude users: what have you built that started as an idea and turned into something much bigger than you expected?