Yupana: El ábaco Inca
yupana
About App
The word Yupana derived from Quechua yupay (count) and is commonly defined as an abacus that was used to perform arithmetic operations and dates back to the time of the Incas.
Now this has a mobile version on Android with which you can learn (In development, for now only the sum) how to use a Yupana.
Developer info