alt Hacker NewsFalling sand games bring back a lot of nostalgia. If you're interested, you should check out dan-ball's version which is one of the progenitors of the genre. Over the years he's added a ton of features, elements, and interactions, to the point where it now has a fluid mechanics simulation for air!
Ha55ii's powder game is perhaps the best of the genre, and the ease of sharing made for a pretty cool online community circa 15 years ago. I remember various calculators / computers created in powder game, along with a bunch of more artistic efforts.