Rothylia simulates a mechanical calculator, with mechanical counters. The operation is simple: you set the numbers in mechanical counters, and result is shown. You can play with operands to see effects in real-time, or tinker with the result and see the operands change accordingly.

Number input is made directly on mechanical counters, using an inovative gesture interface: drag to change numbers, double tap to round (makes it easier to input an exact number) and long press to toggle between negative and positive sign.