Portal is a series of first-person puzzle-platform video games developed by Valve Corporation.

Celestia is a 3D astronomy program, The program is based on the Hipparcos Catalogue (HIP) and allows users to travel through an extensive universe, modeled af…

Overdisk is a visual disk space explorer tool.

Stellarium is an open-source free-software planetarium.

Kerbal Space Program (KSP) is a space flight simulation video game.