Litmus: take atoms, make molecules
A chemistry puzzle in three parts. Build molecules from atoms drifting in a petri dish, then put whole compounds in a test tube and make them react, then do the same with carbon. Two hundred levels, all of it real school chemistry, played on a notebook page.
How to play
The game opens on its three parts, and all three are open from the start.
- Moleculator: every atom has hands. Hydrogen, chlorine and sodium have one, oxygen, magnesium and calcium two, and iron three. Drag an atom in from the Available panel, then drag it to the radical it belongs with, and every free hand grabs the first free hand that comes within reach. Make every molecule on the list. Whatever you move grabs anything it passes near, all along the drag, so the straight line is not always the safe one.
- Reactor: the dish holds whole compounds. Put two in the test tube and they react the way they do in a school lab: an acid and a base make a salt and water, a livelier metal pushes a quieter one out of its salt, two salts swap partners and one falls out as a solid, a carbonate fizzes. What they make lands in the product boxes, and can go back in the tube for the next step. Drag the molecules on the list into the target glass.
- Carbon Chamber: the same bench with short carbon chains. Double bonds open to take on hydrogen, bromine or water, an alcohol and an acid join into an ester, an alcohol turns to an acid, and an ester splits back. Each level opens on a clue that states the rule it teaches, never the answer.
Why it is clever
There is always just enough to make what the list asks for, and something else within reach that would spoil it. In the dish, a hydrogen that grabs the chlorine meant for the iron makes hydrogen chloride, and the iron chloride can no longer be made. On the bench, the compound that reacts with your acid first might be the one you needed later. Lose a molecule the list needs and you can play on, but the level has to be done again.
Tips
- Plan the route before you drag. Move a troublesome radical out of the way first, slowly, through open space.
- On the bench, work backwards from the target: which two things make it, and what makes those?
- Every reaction explains itself on a card. The cards add up to the rules, so read the first few.
Frequently asked questions
Is Litmus free? Yes, completely free to play, with no account or download, in any modern browser on phone, tablet or desktop.
Do I need to know chemistry? No. The first levels teach how many hands each atom has, and every reaction is explained the first time it happens. You will come away knowing some.
Does it work on mobile? Yes. It is built for touch as well as mouse, and the phone and the desktop each have their own levels, laid out for the screen.
Do I have to play the parts in order? No. Moleculator, Reactor and Carbon Chamber are all open from the start, and each keeps its own place.
Is every level solvable? Yes. Every level is checked by making every molecule on its list from what it starts with.
Stuck? Read the Litmus strategy guide
Enjoy a good thinking puzzle? Try Junction or Kaleido, or browse all Zamborin games.