A developer named Kajakkluben has put together a little exploratory game in the vein of Knytt Stories based on the wonderful XKCD panel 1110.
All you do is walk around in it and explore the very big world around you, which spans for miles and miles. You can even discover what other players currently in the world are doing on the statistics page.
Move around with the left, right and up buttons and jump/float around on the balloon with the space key.
Be warned: it’s possible to fall through the floor and into eternal darkness due to collision bugs. That’s not intended as a part of the experience.
It’s a good idea to listen to some Opeth while you’re playing it.
You can play the XKCD game here.