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…

GrandPerspective is open source software for Mac OS X used for disk space analysis.

Stellarium is an open-source free-software planetarium.

DaisyDisk is a disk space analyzer for OS X.

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