The sand falls. You redirect, fiddle, move, block, and modify its consistency. If you spend less than an hour, you probably have a big deadline looming.
The official site didn't work in my browser. If you have trouble, too, try this version.
If you get bored, try the Hell of Sand. The little characters are amusing, though they don't seem very happy--neither would you if sand kept falling on your head.
BTW, if you're feeling lame, you can get instructions from Wikipedia.
hint: watch out for fire and ??? (nuke?)
Both the alternate site to the Sand Game and the site for Hell of Sand each froze my computer using either IE or Firefox browsers. I had to do a forced shutdown. Just thought I would mention it. The original site worked fine and is a lot of fun!