Falling Sand
This is an awesome game I found recently. The game is called Falling Sand and originally appeared on DOFI-BLOG, then later hosted by Chirag Mehta. The game contains four elements (sand, water, salt, oil) that fall in a continuous stream from the top to the bottom of the screen. The game also contains a menu containing the aforementioned elements as well as others with which the user can use to draw shapes and structures. The elements also react with each other as they do in their natural environment (e.g. fire burns oil). It’s actually a great game for kids although adults probably find it more interesting.