years ago, a group of young developers create “Narbacular”, a game where a princes must scape froma dungeon with a single weapon, capable to create portals from two different space points.
a time ago, valve discover this project, hire them, and create portals.
http://www.nuclearmonkeysoftware.com/
you can download it from here, its free.
http://www.nuclearmonkeysoftware.com/downloads/narbacular_drop.exe
