Cross Math
iOSA math puzzle game inside the Duolingo iOS app, played by 100M+ daily active users.
The decision: generate every puzzle live instead of authoring them — a constraint-programming algorithm keeps the numbers honest while the backend produces fresh puzzle shapes in real time, and the Swift UI flexes across every iOS device.
The number: CEO-approved at prototype review, live for 100M+ users — all inside one intern summer.
Live in Duolingo on iOS — 100M+ users