Atooms to Moolecules is a small puzzle game. While Steam belives that this one is a demo, while actually it's more of prototype or anything, as it has all features available and there is no such thing as "Final/full version". Rather, from what I found on Internet, it was one of the small projects of the authour which was to be submitted to "Independent Games Festival".
As you noticed, this puzzle game is based on chemistry. If to be more certain, it's based on linking elements. It doesn't have a lot going on aside from this. It also doesn't have a lot of customization in options, where you can't even change resolution for some reason. What it has, is 8 normal challenge levels that unlock progressively and a Lab Setup.
Main gameplay there is to connect atoms into molecules, linking them together. It uses the very basic rules of chemisty, in that each atom has it's own amount of links, and molecule have to have all it's atoms's links used to be count as complete. For sure, it's not something what you seen before, at least not me, and it's good that it's not another tetris. But having only this, it somehow fails to excite us, bringing a dull repetive experience once you figure the basics.
Normal mode is hardly brings a challenge. Most of levels are "connect atoms", only some have some kind of time limit and two having link-breaking elements. Somehow, the basics of gameplay aren't all that iinteresting, and these levels don't help much.
Lab Setup is dissapointing, as there isn't any reason for sandbox gameplay there. There is no crazy experiements, since you are the one who connects atooms and ability to place capsules and other such things hardly matter there. Only electricity is the one that interacts with atooms in any noticeable way, breaking their links.
This game does have the minimalistic cute style to it, and there is nothing much else to it, being something on the level of Flash game, with some nasty usage of blur. Now, there is only a single piece of music, which playes non-stop during whole game, never stopping or changing volume, as if somebody just launched a music player somewhere else. Said music, which can be heard at trailer, isn'y exactly varied or good enough, so it gets annoying pretty fast.
If that wasn't a free game, I would have rated it down. But you know, this game some uses. Since it uses the basics of chimestry, it can be used to understand said basics better. So if you are complete zero at chimestry, you got a reason to download and try this.