Nebula is a toy for composing a sky, not a map of one.
You drift a few glowing clouds across a field of stars, tint them whatever hue suits the mood, scatter star-glows and a single planet, then dial in grain and a soft vignette until the scene settles. Everything answers immediately — hue, density, star count, glow, grain, vignette, the whole palette — and a slow twinkle keeps the picture alive while you work. There is a randomise button for when you would rather be handed a universe than build one.
Scenes you like go to a personal gallery, where they can be reopened, adjusted, duplicated into a different palette, or set as the app's own backdrop. None of it pretends to be astronomy: the skies are invented, so there is nothing to get right and no catalogue to be faithful to. That is the point of it.
Scatter four hundred stars at random over four hundred patches of sky and one patch in three will be empty.
Anyone who has built a star field by hand knows the feeling: the random version looks wrong — clumped here, bare there — so you nudge it until it looks even. But even is precisely what random is not. The share of empty patches follows from nothing more than the chance of a single star missing a single patch, raised to the number of stars, and it is a much larger share than the eye expects.
Four hundred stars over four hundred patches averages exactly one star each, and still leaves 147 patches — 36.7 % of the sky — with nothing in them at all. Meanwhile somewhere in the field a patch is holding five. Spreading stars evenly is a decision; it is not what randomness does.
The same seed every time, so the drawn figures are reproducible. Shaded squares are patches with no star in them. The expected count comes from k²(1 − 1/k²)^N; the drawn count is one sample and wanders around it.
Not on this page: Nebula's own cloud layers, its star and grain textures, its palettes and its gallery. The arithmetic above is the ordinary mathematics of throwing things at a grid, and it holds for raindrops on a pavement as readily as for stars. It says nothing about how the app looks or feels.
Four things stated without decoration.
No connection is opened, so there is nothing at the far end of one. A tunnel, a plane and a desk all produce the same behaviour.
Nothing to join, nothing to sign in to. The gallery is a folder the app keeps to itself on the device.
No ad framework is linked into the build and nothing measures what you do with it. If that changes, the policy is redrawn before the release goes out.
They remain on whichever handset composed them. Not one has ever reached us, because no part of the app was built to send one.
The company behind it
Director: Helge Skaret
Sælshagadn 82, 2940 Heggenes, Norway
Mail: stjerne@foxas.homes
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