Prompt: Build a fun, extremely smooth typing game end to end. It should measure your speed but be genuinely fun to practice with, and it should adapt up and down to your skill so progression feels fair. Free website, global leaderboard, optional GitHub or X username to show your avatar (no sign-in). Fully responsive. Visually test everything, test the mechanics, and keep iterating until it's something you're proud to show off as a demo of Opus 5.5. Use Sonnet 5.5 subagents for well-defined parallel tasks, track usage and timing separately, and open it in my browser when done.