This quick snappy soroban abacus app has timed addition and subtraction sums in single or multiple exercises with the ability to repeat or go forward to sums within the app. Great user interface. Lively competitions with friends are possible through the timed results. Use for mental calculation. Competence and skills level of the abacus will quickly accelerate at a far greater rate as the user can practice anywhere, bus, train, wherever! You will become absorbed with Jimmy Abacus digital Soroban.