Header image of a close-up of a soroban

About this site

The site mainly started around the idea of an online generator of exercises to practice the soroban. It evolved a bit with the addition of pages with mental calculation software; then the virtual soroban and its "tutorials" and the possibility to get an operation being displayed on the virtual soroban. A forum was needed to overcome the limitation of disqus, which is a great commenting system anyway.


You don't need a Paypal account if you don't have one

Donations will be used for the possible cost of the site that may arise in the near future with the new pricing policy of Google App Engine. Otherwise, I will take them as a tip for the work I made on this site. We thank any donor in advance of their good gesture.

You may need a currency converter from/to €, you could give a try to the one at xe.com. Beware that Paypal does not use the same exact exchange rate that xe.com

Bitcoins accepted here

bitcoin logo

We are now accepting donations in bitcoins.

You can either use the new Bech32 SegWit address ::bech32::. This is the preferred method.

However, for backward compatibility, we provide also a P2SH address ::p2sh::

qrcode for bech32 bitcoin address
Bech32 bitcoin address
qrcode for p2sh bitcoin address
P2SH bitcoin address

Technologies that are used to create this site

appengine logo google analytics logo Sendgrid python logo reportlab logo html5 logo jquery logo bootstrap logo atom logo git logo ubuntu logo


On the subscription page, a cookie is used to remember the settings you have chosen and is then immediately erased.

On the forum, a cookie is used to remember your username.

Analytics Tracking

As already shown above, this site is using Google Analytics to collect data about the site visitors. You can opt-out from Google Analytics on this site by clicking this link. Note however than we need to use a cookie to remember that you have opted-out.