Octet: Molecule Puzzle

Octet is a chemistry-themed puzzle with a single rule: every atom must end up with exactly as many bonds as it has arms. Hydrogen has one, oxygen two, nitrogen three, carbon four. Place the atoms on a small hex grid, join them up, and the board checks itself. When every arm is filled and everything is connected, you have built a valid molecule, and Octet tells you the name of the one the level is based on.

No chemistry knowledge needed. If you can count to four, you can play.

HOW IT PLAYS
• Drag atoms from the tray onto the board, or tap an atom and then tap a cell. Use whichever suits you, or both.
• Atoms that touch bond automatically. Tap a bond to make it double or triple, or to break it.
• Each atom shows its arms as pips around the rim, so you always know what is left to fill.
• There is no hidden answer to match. Any arrangement that satisfies every atom wins.

WHAT'S INSIDE
• 100 levels across six tiers: real molecules from water and ammonia to benzene and pyridine, then two tiers of generated challenges up to twenty atoms.
• Endless mode after the campaign: an unending run of numbered puzzles at mixed difficulty, the same for every player, never repeating a molecule.
• New ideas arrive one at a time: single bonds, then double bonds, rings and branches, triple bonds, and decoy cells that are not part of the answer.
• A new daily puzzle every day.
• Three stars per level for finishing at or under par.
• Unlimited undo, with no star penalty.
• Hints when you are stuck. A hint places one atom or fixes one bond.
• Short levels. Most take under two minutes, so a round fits anywhere.

MADE FOR PHONES
• Portrait, one-handed play. Drag, tap, or both. Either style can be switched off in Settings.
• A clean, high-contrast board that stays readable on small screens.
• No account needed. Progress is saved on your device; sign in with Google Play if you want it backed up to the cloud, with achievements and leaderboards.

A NOTE ON THE CHEMISTRY
Octet uses real valences and real molecules, but it is a puzzle, not a simulation. There are no charges, lone pairs or 3D shapes, and the hex layout is a game board rather than molecular geometry. The name is a nod to the octet rule that gives those elements their valences.

Octet shows short ads between levels, and a single purchase removes them for good. Hints stay available through an optional ad.