Good, but I wish it had a couple more functions – Abacus' brain Review

This is the best app that I've found for drilling rapid addition on the abacus. I use it daily, but I do wish three things were different. 1) that you could turn off the sound. I've had to tuen off my ringer to avoid the sound, then forgotten to turn it back on an missed calls. 2) better instructions. I didn't realize you have to pass a speed round in order to practice with more than 1 digit. 3) Addition only. I wish you could choose subtraction only or mixed Addition and subtraction. Simple multiplication or division would be nice too. Overall I really enjoy it, hopefully new versions will include these features.
Review by Yoaz Shelef on Abacus' brain.