I built a physics claw machine + rigged blackjack game with Claude, balanced with Monte Carlo sims

https://pgskizzes.itch.io/clawtastrophe My role was design, direction, balance calls and a lot of playtesting. Claude wrote most of the code. What worked: Investigate, propose, implement. No code until the approach was agreed. It kept a 1,700-line single file sane. Make it test its own work. Claude ran the game headless in Playwright: dropping prizes into the chute, playing stacked hands, checking for console errors after every change. Measure the balance. The blackjack engine is a shared module, so a Node sim runs the exact rules the game uses. Hundreds of thousands of hands per tweak. The base table is -4% for the player, and every item's effect has a measured number. Playtesting still mattered. The worst bugs (9s reading as 6s, prizes escaping the glass, arrow keys dying inside the itch.io iframe) were found by playing the game, not by reading code. Stack: three.js, cannon.js, WebAudio, one HTML file.