Lucky Wheel

This is a personal, solo project — product idea, product design direction, Android implementation, automated testing, and release preparation are all my own work. It's built on top of a reusable Android product foundation I maintain separately, reserved for the app-specific logic: wheel/prize management, the weighted-selection engine, spin animation, and history.

1. Technical challenges

   The core challenge was making a weighted random draw feel fair and trustworthy: the winner has to be selected correctly according to each prize's configured weight, the spin animation has to visually land on that exact result without looking ambiguous, and a rapid double-tap or an accidental back-press during the result dialog must never be able to record two results for one spin.

   How I approached it

   The winner is selected first, using cumulative-weight random sampling — not a naive equal-chance pick — before any animation runs. The wheel's visual slices are deliberately equal in size regardless of weight, so probability and visual layout stay decoupled; a separate geometry calculation then computes the spin's landing rotation, with a safety margin that nudges the stop point away from a slice boundary so the result never looks ambiguous. Saving or skipping a result after the spin is guarded by a single-flight state check, confirmed with a dedicated concurrency test, so at most one history record can ever result from one spin.

A release-readiness review of the app found it substantially feature-complete but identified two concrete items to fix before publishing — a placeholder privacy-policy link and a missing way to delete a wheel once the free-tier limit is reached. That's a normal, healthy part of shipping software: feature-complete isn't the same as release-ready, and a dedicated release check is what catches the difference before real users do.

• Android Development
• Offline Support
• Release Support
• QA & Testing