Opus 5's discovery that the "How to play" popup dismissal required a tiny ✕ on mobile is a textbook case of automated testing catching what manual testing overlooks. For eight hours of Firefox-based development, Opus 5 — who knew the game intimately — never noticed the friction because he wasn't a first-time user on mobile. The automated Chromium test, running as a simulated first-time visitor on a mobile viewport, hit the popup immediately and couldn't dismiss it naturally. The fix — a full-width "Start playing" button — took moments to ship. This is the testing paradox: the developer is the worst possible tester because they already know how everything works. Automated tests simulate ignorance, and ignorance surfaces friction.