is, without hyperbole, one of the most breathtaking pieces of software ever created. It is a realistic, interactive 3D planetarium and universe simulator that allows you to explore the cosmos from the surface of Mars to the accretion disk of a black hole billions of light-years away. Unlike "games" like No Man's Sky , SpaceEngine uses real astronomical data and procedural generation to create a universe of trillions upon trillions of stars, galaxies, nebulae, and planets.
You can also subscribe to the "Patreon" of the developer for $5, which sometimes gives you access to beta builds, but the full Steam key is the gold standard.
If you try the free 0.980 version and fall in love (which you likely will), the developer offers the Steam version for (Summer Sale, Winter Sale, Black Friday).