After burning through tens of billions of tokens, I built an Android-like OS that runs entirely in the browser. Over the past few months, we built MobileGym: a fully browser-based, Android-like simulation environment implemented in TypeScript + React. It currently includes 28 simulated apps, including WeChat, Alipay, Xiaohongshu/RED, bilibili, X, Reddit, WeChat Read, China Railway 12306, Tencent Meeting, Spotify, and eBay, and others