This application is a simple Japanese abacus (soroban / そろばん). It has a free mode where you can use the abacus freely, and a challenge mode with 4 operations (addition, subtraction, one and two digit multiplication, and division) and 3 difficulty levels (easy, medium, hard) where you must race against the clock to perform calculations.
Also has a custom challenge mode where you can set the number of questions, type of questions and difficulty.
(This is just a hobby project I'm doing for fun. This app is free and doesn't have in-app purchases or ads).
[PERMISSIONS USAGE] This is a description of how permissions are used in this app. Vibrate: The application can vibrate the phone to give user feedback. This can be enabled/disabled in the Settings screen.