The first can be proven with the provided benchmarking tool.[1]
As for the second, I agree that the source of those "units sold" should be cited.
As for the second, I agree that the source of those "units sold" should be cited.
They claim their algorithm is impossible to solve using robots... When it is obvious that it isn't impossible...
The purpose of the example is to give you a basis on which you could implement an effective CAPTCHA.
The claim of "difficult or even completely impossible for robots" applies to CAPTCHAs using the above techniques, which are not used in the example.