I've since made it so chemicals that cancel out cannot be mixed together at all, e.g., the hotbar will flash red and error if you try to add a plasma to a water, and removed all circular reactions. I may rework this again.There might be situations when the player wants to just remove one chemical without removing all of them, so they would use the "opposite" chemical.
I'm a bit against it due to it limiting the amount of combinations you can make
Ideally all combos should be made with one or two taps with your fingers in correct positions like
(this is even more important in your game compared to magicka, because the same fingers are used for movement)