[_Adam]

Assuming this isn't an April Fools joke...

This kind of interface creates a terrible user experience. I've seen them before, and they always suck. The main issue is that you remove all context from the interaction. I don't know where I am relative to the entirety of the content. Furthermore, I can't jump to the point that I want.

It's disorienting and infuriating, and after about 10 seconds of exercising my middle finger (in multiple ways), I close the tab and add the site to my mental list of "examples of shitty UX".

Fortunately, this isn't the first such example, so I can provide solid evidence of how horrible this concept is. Ironically, it's the Famo.us Angular integration documentation...

https://famo.us/integrations/angular/#/1

[kenbellows]

Not disagreeing with your overall point regarding the usefulness UX of this sort of interface, but unlike the Famo.us demo, Space.js seems to maintain the scroll bar on the right window edge, which allows you to keep a sense of where you are within the document and to jump where you want within it. Also, the down arrow alleviates the strain on your middle finger nicely, as will clicking and dragging the scroll bar.