A downloadable game for Windows, macOS, and Linux

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Caelium Alpha is a digital orrery sandbox.

An orrery is a model of the solar system; small worlds you can carry with you. Make your own little planetary system orrery by adding planets, moons, and adjusting properties. Then marvel at the possibilities in the universe :)

If you wish to rate the game on Ludum Dare, then try out the LD38 Edition in the downloads below. If you want to play the game for keeps, then download the Post-LD Edition (not LD38 Version) in the downloads below.

Caelium Alpha is free to download. But just in case anyone wishes, you can pay for the downloads, but you don't have to.

Also note that all of the screenshots here are for the Post-LD Edition.


  • Start off with a star and adjust its properties (radius, color, etc.)
  • Add planets to the star, and adjust their properties
  • Add moons to each planet, and adjust their properties
  • Automatic padding between every astronomical body, fully adjustable
  • Properties include color, radius, padding, axial speed (rotation), and orbital speed (revolution)
  • Guarantee that most stars spawned will have a unique name
  • Planet and moon names are based off stars (just like real exoplanets)
  • Stars, planets, and moons will spawn with random surface texture (not adjustable at this time)


  • WASD or Arrow Keys:
    • Move
  • Left Shift (also Right Shift in Post-LD Edition):
    • Hold to move faster
  • R:
    • Zoom in
  • F:
    • Zoom out
  • 4:
    • Reset zoom
  • Right Click:
    • Select Star or Planet (or deselect by clicking on nothing)
  • Esc:
    • Quit


For the Post-LD Edition:


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Click download now to get access to the following files:

Caelium Alpha - Improved Post LD Edition - macOS 39 MB
Caelium Alpha - Improved Post LD Edition - Windows (64-bit) 37 MB
Caelium Alpha - Improved Post LD Edition - Linux 51 MB
Caelium Alpha - LD38 Edition - Linux 49 MB
Caelium Alpha - LD38 Edition - macOS 37 MB
Caelium Alpha - LD38 Edition - Windows (64-bit) 35 MB

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