The "tutorial" only goes through how the buttons work (they are more confusing than necessary). I haven't studied chemistry in several decades, so I wanted to see if I can relearn a little bit. But this program seems to only check if you remember a formula. It doesn't give me any advice about valency or stoichiometry, so I don't know how many atoms are required to make a molecule. For instance, I remember that oxygen atoms come in pairs, so you need 4 hydrogen atoms to make 2 water molecules. But if I...