ApertureScience is to develop Portals, a single player puzzle game. The objective of the puzzles is to create an enter and exit point with a portal gun, whether it be transporting to a ledge,exit, or avoiding seemingly impossible obstacles, Portals should be equally as fun as the Half Life: Episode Two that it is shipping with.
The "Aperture Science Portal Device" is to be released this Fall, but various Portal mods already exist for Half life 2, and various other clients such as Prey. Some of these mods follow the same level design as demonstrated in the portals preview below.
Compare to StrikerMods