Click a world for its dossier, or the star for the star's. Scroll on the map to zoom. Space bar starts and stops time.
Worlds marked with a green edge have something in the atmosphere that chemistry alone does not explain.
How the date becomes a solar system
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01
Light a star
The seed draws a stellar mass, and everything else follows from it: luminosity goes as mass to the three-and-a-half, which fixes the surface temperature, the colour, the spectral class, how long the star will last, where water freezes and where the habitable zone sits.
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02
Fill the gaps
Orbits are laid down from the inside out, each one between 1.4 and 2.2 times the last, the way real systems tend to space themselves. Inside the frost line you mostly get rock; outside it, gas and ice. Mass sets radius, radius and mass set gravity, gravity decides what atmosphere survives.
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03
Work out the weather
Equilibrium temperature comes from the star's output, the orbital distance and how much light the surface throws back. A thick atmosphere adds a greenhouse on top. A world that lands between roughly 250 and 340 kelvin, with air and enough gravity to keep it, is allowed to be interesting.
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04
Set it running
Positions come from Kepler's equation, solved by Newton's method every frame, so the planets slow down at the far end of their ellipses and hurry through the near end. Moons run on their own clocks. Nothing is animated on a timer — it is all one number, integrated forward.
Nothing here is stored and nothing is real. Tomorrow the star goes out and a different one takes its place, with different worlds and different names, and this system will not exist anywhere again. If you want the same number doing other work: the Observatory scatters it into a night sky, the Atlas raises a coastline out of it, the Menagerie breeds animals from it, the Almanac writes the day's news with it and the Chimes play it.