I came upon this, and thought it was pretty cool:

http://dan-ball.jp/en/javagame/dust/

It's this game where you create particles(or dust/powder/dots/whatever) that have different elemental properties, and you can put them together for reactions. Some are obvious like oil burning up when exposed to fire, and metal being rusted by water, but other reactions are more subtle.

It also has part of a wiki dedicated to it: http://danball.wikia.com/wiki/Powder_Game

This game has about a thousand different variations.

ooh, I remember this. I completely forgot about it...

This game is an excellent time killer.

ohey, this game

Try combining water and salt to get seawater and then expose Vine to it.

Vine=grows over all the things, without exception
Saltwater=turns Wood and Vine to Sand