Mental arithmetic has been a hobby of mine for a while. It's fun and good exercise for your brain.

When I switched to iOS, I couldn’t find a decent app. Most had ads, sign-ups, excessive gamification, or mandatory subscriptions, and none were customizable enough. So I built my own.

Athena Math lets you

- Practice operations not normally found in mental math apps: modulo, square roots, percents, GCD and LCM - Tailor each session: set your time or problem limits, choose digit ranges (1–5), mix digit lengths (e.g. 55 + 436), and select any combination of operations you like. - A detailed stats screen that shows the time you spent on problems, problems per day, percent correct, etc. All graphs are filterable. - A history screen that shows all your sessions. - You can import and export your history for offline analysis or to transfer - Offline tutorials are included for all operations - Lastly, you can use it immediately. There are no accounts.

So far, it's received a positive response from the mental math community. It's an incredible feeling to have people actually value my work enough to pay for it. (This was my first app).

I've had a lot of fun building Athena math and using it myself. Practicing obscure operations like GCD, LCM and square roots has taught me to see patterns in numbers that I didn't see before. Overall, it's improved my number sense.

It's built in React Native + Expo/EAS. I use Fastlane to manage app store metadata (and store in version control), and it's using a serverless AWS backend for payment verification. History is stored locally in an SQLite database.

It's free to use! You're limited to 12 sessions daily, but if you wanna keep using for free, you can simply delete your daily sessions. You loose history and stats, but it's an option. You can also just set the time limit to infinity.

I know mental math is not the sexiest market, but I'd love feedback from the HN community -- on the app, the UX, or the technical setup. Any ideas for improvement? What are your thoughts?

Thanks for reading and happy hacking!