Boing Boing linked today a quick, fun flash game called 400 Years, Here's the link to play, in which you play a strange little stone totem who has only 400 years to stop some great catastrophe. It took me a little playing around before I realized that you didn't just get to wait forever -- that whenever you waited, you were wasting time before the catastrophe hit, and you could conceivably wait the whole four hundred years, and lose. I did fine the first time through, then I decided to check out what happens if you don't make it.
At top waiting speed, you only pass about a year a second, so it took a while.
While you're waiting, you see the world change before your eyes. Where I stopped to lose the game, I saw two trees grow from saplings to extraordinary heights, then fall down, and new saplings sprouted in their place.
The game involves waiting for huge periods of time, but it also occasionally involves doing stuff -- manipulating physical objects like seeds you need to plant. These seeds dry out and go away if you hold them while you're waiting, so sometimes you need to figure out how to get around without using the tricks of the long time scale.
Loss-condition spoiler below the fold:
You don't actually get to see what the catastrophe was that you failed to stop, if you don't beat the game. The waiting stops suddenly, the earth begins to shake, the screen goes white, and then you see an image of burning trees, and the message,
TOO LATE... THE WORLD HAS BURNED TO ASHES.
The win/lose conditions are pretty cool, but the story you see unfolding on the timescale of centuries is even more beautiful. I highly recommend this game. Here, again, is the link.