Thanks for this website! I read a few other articles, thought I'd be bored quick but ended thinking "it's already the end?". Seems like they're putting into words many principles I found out for myself, a pleasure to read. Wish I could afford the sub.

Can something similar be done with phone number verification ?

Probably you still can define a fractal by changing slightly the construction.

Anyways, here's my take for a generalization : http://imgur.com/qD0aZ