Months-long Claude-built Rummy 500 game opens free on web, rebuilt with Opus 5.5

AIandDesign · x · 2026-09-24

Developer Marco van Hylckama Vlieg released the free web version of his Rummy 500 game, originally created with Sonnet 3.7 via Augment Code and taking months to get right.

He later overhauled it with Claude Opus 5.5, fixing obscure bugs and making hard mode brutal. The web version is free with no ads or IAP; monetization is a $4.99 iOS app. A good case study in long-horizon AI-assisted game development across model generations.

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