Kalvro

Kalvro is a math trainer built for anyone who wants to sharpen their mental calculation skills — whether you are a student working through basic arithmetic or an adult looking to keep your mind sharp.

The app presents arithmetic problems across different difficulty levels and lets you answer using a built-in numpad. There is no keyboard to fumble with, no distractions, just numbers and your thinking.

Everything works offline. No account, no sign-up, no sync. Your progress and stats are saved locally on your device and stay there.

Features include:
- Arithmetic problems covering addition, subtraction, multiplication, and division
- Built-in numpad for fast, focused input
- Multiple difficulty levels to match your current skill
- Progress tracking so you can see how you improve over time
- Onboarding walkthrough on first launch to get you oriented
- Clean, readable interface with a decorative background and emoji-accented UI

Settings let you adjust the first day of the week, default sort order for your results, and reset the onboarding tutorial if you want to revisit it.

There are no ads, no purchases, and no data ever leaves your device.