Atom By Atom

You start with hydrogen. A cloud of it drifts past; an extractor pulls atoms out; a tube carries them to the black hole, which is hungry, specific, and never satisfied for long.

Then it asks for oxygen. Then water — which means two hydrogens and an oxygen have to arrive at a bonder at the same moment, in the right proportion, without either line backing up. Then hydrogen peroxide. Every contract you complete unlocks the next element, the next machine, and a slightly less forgiving molecule.

What you build

• Extractors pull single atoms from element clouds that drift through the map.
• Matter Tubes carry atoms. They do not merge, they do not sort, and they back up when the next machine is busy — which is most of the game.
• Dividers split a flow so one extractor can feed two bonders.
• Bonders join atoms into molecules using real valence rules. A bonder fed the wrong ratio simply waits.
• Wormholes let you skip the geometry when the geometry is the problem.

Why it’s interesting

Chemistry gives the game a rule set it didn’t have to invent. Water is H₂O because it is; the puzzle is delivering exactly that, at rate, forever. Later contracts — polymerisation, cyclisation — turn a tidy little line into something that has to be planned.

Demo

The free demo covers the hydrogen tutorial and the first four contracts (H₂, O₂, H₂O, H₂O₂), plus a sandbox mode that keeps going after the last one. It runs in the browser and on Windows, Mac and Linux, and saves can be exported as a code and brought into the full game.

Atom By Atom is out now on Steam, released on 3 November 2026. Get the full game or try the free Steam demo. The browser demo is also available on itch.io.