Score: 0
Stellar Core
Peak: H-1
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About Stellar Forge

Fuse atomic nuclei from hydrogen to iron in this free online nuclear fusion game about stellar nucleosynthesis and binding energy.

Stellar Forge is a free online nuclear fusion game where you slide atomic nuclei across a grid and fuse identical pairs to climb the periodic table from hydrogen to iron. It plays like a 2048-style puzzle, but every merge follows the real sequence of stellar nucleosynthesis inside a massive star.

Each fusion in the game mirrors a real burning stage: hydrogen pairs build helium, helium builds carbon through the triple-alpha process and alpha captures carry you through oxygen, neon, magnesium and silicon to calcium and iron. Your score is the energy released as nuclei bind tighter. The binding energy per nucleon curve peaks at iron-56, which is why forging iron is your summit: fusion beyond it absorbs energy instead of releasing it, shown as a red score penalty.

That cliff is why massive stars die. Once a core fills with iron it can no longer release fusion energy to resist gravity, so it collapses and explodes as a supernova. The explosion seeds space with gold, platinum and uranium, which is why heavy elements spray onto your board after the collapse. Splitting uranium releases fission energy, the mirror image of the climb you just made.

Key Science Concepts

What You'll Learn

Grade Level: Middle School, High School, College

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How to play

  1. Slide the Core Swipe, drag or press arrow keys / WASD to slide every nucleus across the grid.
  2. Fuse Identical Twins When two matching nuclei collide they fuse into the next element and release energy as score.
  3. Climb the Chain Each merge climbs the fusion ladder: H to He to C to O, just like a burning stellar core.
  4. Iron Is the Wall Iron-56 is the tightest-bound nucleus. Fusing past it consumes energy and drops your score.
  5. Supernova Spray Forge iron and the core collapses, spraying gold and uranium bonus nuclei onto the grid.
  6. Bank Your Star A full grid with no merges means core collapse. Use Exit to bank your score in time.

Frequently asked questions

Is Stellar Forge free to play?
Yes. Stellar Forge is completely free to play in your browser. There is no download, install or account needed.
What grade level is Stellar Forge for?
Stellar Forge is designed for Middle School, High School, College students and works well as a classroom activity or homework.
Does Stellar Forge work on phones and tablets?
Yes. Stellar Forge runs in any modern browser on desktop computers, Chromebooks, tablets and phones in landscape mode.

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