Nucleo Play now
Free idle game · the real elements

Forge the universe, atom by atom.

Start with a single hydrogen atom. Synthesize your way through all 118 elements, build real moons, planets and stars, and collapse it all in a supernova to come back stronger.

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FreeNo downloadNo account neededPhone or computer
A glowing atom at the center of a galaxy, circled by element tiles
118real elements to collect
30moons, planets, stars and galaxies to build
49real molecules to synthesize
96real spectra to identify
Elements

Start with hydrogen. End with oganesson.

Spend energy to synthesize atoms. Every element feeds the one below it, so your chain grows while you watch, and keeps earning while you’re away.

  • Elements arrive in the order they’re common in Earth’s crust
  • Every 25 atoms of an element double its output
  • Facts about every element in the Catalog
The Elements screen: osmium and gold cards with their atoms and energy
Supernova

Collapse it all. Come back stronger.

When a cycle has released enough energy, trigger a supernova for stardust that multiplies everything. Later, neutron stars collide in kilonovas, and dark matter opens the deep sky.

  • Stardust, neutrons and dark matter, each stronger than the last
  • Permanent upgrades bought with isotopes
  • Levels and a weekly leaderboard
The Stars screen: supernova and kilonova panels
Cosmos

Build the Solar System from your leftovers.

Surplus atoms become real worlds: the Moon, Mars, Jupiter, Halley’s Comet. Then build the Sun, a pulsar and whole galaxies, each with its own bonus and its own page of real science.

  • A living orrery of everything you build
  • Send probes to your worlds for rare specimens
  • Comets, meteor showers and solar flares while you play
The Cosmos screen: an orrery of the Sun with planets and moons
Spectroscopy

Read the light of the stars.

Every element glows at its own colors. Name the element behind a star’s spectrum, using real lines measured by NIST. Get them right and time itself speeds up.

  • Moving stars, starlight and mixtures unlock as you progress
  • Know an element by heart and its lab spectrum disappears
  • Complete a family in your Spectra collection for a permanent bonus
The Spectra screen: a star's emission lines and four element choices
The periodic table

All 118 elements, all in the game.

Hover or tap an element to read about it. In Nucleo they arrive in the order they’re common in Earth’s crust, so oxygen comes first and oganesson last.

Swipe the table sideways to see all of it.

Facts from the Nucleo Catalog. Crust abundances are typical values in parts per million.Collect them all →
And while it ticks

Always something to do.

⚗

Chemistry

A lab bench of 86 real reactions to discover: mix ingredients under heat, sparks, light or cold.

🔭

Observatory

One look through the telescope a day. Log over 12,000 real galaxies, clusters and nebulae.

🛰

Probes and specimens

Send probes to the worlds you’ve built. They bring back meteorites, comet dust and presolar grains.

☼

Daily research

Three small goals every day. Keep a streak for a bigger energy bonus.

★

Mastery and achievements

121 achievements, five mastery stars per element, and titles to show on the leaderboard.

☄

Cosmic events

Catch comets as they streak past, and make the most of meteor showers and solar flares.

⇄

Play anywhere

Install it on your phone like an app. Move your progress to another device with a backup code.

Optional · Enjin

Collectible cards, with bonuses in the game.

Nucleo has a collection of cards on Enjin: the element families, the Sun, Jupiter, the Crab Pulsar, Messier 87 and more. Hold them in your Enjin Wallet, sign in, and each one gives its bonus in the game. Your wallet also keeps your progress, on any device.

View the collection on nft.io ↗

Entirely optional: the whole game is free to play without a wallet or any card.

Nucleo Genesis card
GenesisEnergy ×1.5
The Sun card
The SunEnergy ×1.2
Crab Pulsar card
Crab PulsarRays +50%
Noble Gases card
Noble GasesFamily +25%
Europa card
EuropaExcite +50%
Messier 87 card
Messier 87Dark matter +25%
13.8 billion years in the making

The universe is waiting.

Your first hydrogen atom is one tap away. Free, in your browser, no account needed.

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