[calvins]

What you're missing is that Bret Victor isn't the author of that web page.

If you want to some of his inspired UX, view https://vimeo.com/67076984

[vxNsr]

Ah thanks, I knew someone with the amount of work (just from that page) wouldn't make such an obvious blunder.

[buovjaga]

If you mean http://worrydream.com/ it is made by Bret Victor himself.