Great puzzle game. You have to create combine and alter molecules to create a specific compound. Game doesn't provide any real instructions but if you give it a few minutes of trial and error you should be able to figure it out. I only played through the main puzzles but will probably come back to it and try the extra puzzles as well. Puzzle 33 was definitely the most challenging for me. I believe there are 64 molecule puzzles total and a solitaire game resembling FreeCell.