Most bingo/tambola caller apps I found either required internet for ads, analytics, or remote syncing. For community halls and senior centers (where this is often used), connectivity is unreliable — and I didn’t want gameplay to depend on network state.

So the app:

Runs fully offline (no API calls during gameplay)

Uses a cryptographically secure RNG for number generation

Doesn’t collect personal data

Doesn’t require account creation

The hex verification system was added after running into disputes during larger games. Instead of manual checking, each card can be validated deterministically against the called sequence, which made competitive sessions much smoother.

If anyone is curious about implementation details (RNG choice, QR card generation approach, state handling, etc.), happy to go deeper.

Also very open to critique — especially around UX clarity for large-screen TV mode.