You should have a look to UNO [^] platform.

It is almost correct. Belgians still use 80 (quatre-vingts). But you are perfectly right about 70 and 90.

I don't think this is really wrong. This is probably due to confusion between modulo and remainder. There seems to be the same for positive numbers. But for negative numbers, there are different. Remainder work as expected. But modulo work as following: returns the difference of the first number, and the biggest integer (possibly negative) multiple of the second number that is less than the first number. So in our example: -1 - -20 = 19 That's why lot of programming languages have 2 "modulo" operators, one for modulo operations and one for remainder operations.

OK it makes sense. Thank you for the feedback.

It seems a good idea. I am iOS user so I didn't give a try to your app. However, I think you should add the user name to the site key. This would add some additional text to hash and it would help if someone forget it.

probably a confusion with Tk ?