It’s a really gorgeous piece of cartooning. Do what it tells you, follow the alt text.
The best part I found so far:
This is seriously amazing.
I’m lukewarm on xkcd — lately it goes for easy pandering far too often for my taste — but this is, in fact, amazing. The only reason I didn’t waste more time is because I got stuck underground after going off-path, like I disabled clipping or something.
If you want to cheat, someone put together a zoomable version.
The first time I looked at it, scripting was blocked and I just assumed I could drag the picture over whatever and the fourth large panel would frame things both sad and wonderful no matter where I dragged it. I should probably stop assuming that everything is high-concept art.