Substance is a puzzle retro-style game where you fuse chemicals together to make new chemicals in order to complete a level. It features a level editor, so that you can create puzzles for yourself, other people or just to add to your big puzzle library.
Substance also uses Greek letters to reference each of the different chemicals. That's... good!
One word of warning before you download and play this game: this game requires the .NET framework to be downloaded on your system; the version needs to be at least 4.0. Here's a link for your convenience: http://www.microsoft.com/en-gb/download/details.aspx?id=17851
Full version (large collection of music, 500mb):
Partial version (only 3 tracks of music, 19mb):