Decent point on not knowing how big your window size is - think I'll update to include a width counter on the start screen.
Reason for the resizing down at the start is simply so only certain parts of the animation show at different times. It means I can control what width the animation is being viewed at, as otherwise I'd have to animate everything across a very large width potentially, which would be pretty time consuming, as this could be huge. Think with the feedback I've had, will release as a non media query animation as well when I get chance.
It took me a while to realize that the resizing was the whole point -- the scene animates as it gets wider.
There's nothing ground-breaking here, but neither is there in many of the XKCD stunts that we fawn over here. I think if you just describe it that way we'd all know what's going on.
I have tabs, so I had to pull the tab out to a new window (or else risk resizing everything that is already the way I want it).
I don't know how wide my windows are! I had to pull up the javascript console and read "window.innerWidth" and 320 is amazingly small for me.