I wanted to play "Oni Keisan" on my iPhone!
That's why I created this N-Back brain training app.

What is this training?

Solve calculations while remembering the answers from a few questions back.
Juggling "memorizing" and "calculating" at the same time gives your brain a real
workout.

Features

◆ Two Input Modes
- Tap Mode: Quickly tap the answer
- Handwriting Mode: Write numbers directly

◆ Build Daily Habits
- Set daily play goals
- Track your streak
- Record how you're feeling today

◆ Track Your Progress
- Accuracy trends
- Level-up history
- Play history

◆ Customize Your Way
- Adjust question count & time limits
- 3 color themes
- iPhone & iPad support

Perfect For

- Those who want to play Oni Keisan without a dedicated game console
- Anyone looking for a quick mental exercise
- People who want to build a daily habit

Just 5 minutes a day. A casual brain training experience.