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.
OP here. I built this because I realized most health apps are just data vacuums for insurance companies and also look like they were build 20 years ago.
The hardest technical decision was not using a backend. I’m using the Android FileSystem API to store everything in a local encrypted JSON blob. It makes cross-device sync harder (I added a manual xml export to ensure you can save data for yourself and family), but it guarantees that if my server goes down (or I get hit by a bus), the app keeps working forever.
I also stuck to Vanilla JS + Vite instead of React/Flutter to keep the file size less.
I'd love feedback on the PDF report generation—I'm drawing charts to a hidden Canvas and then injecting them into jsPDF. Thoughts?
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.