Portal: Chamber 21 Map
Chamber21 Readme To install unzip file and place map files into your folder named Steam\SteamApps\username\portal\portal\maps to play the map, run portal, open the developer console and type “map chamber21” or “chamber21advanced” then hit enter
This map is 100% playable all the puzzles work. With almost no bugs. Although there are a few ninja solutions to some of the puzzles. This map uses the principle of angular portal entry in some of the puzzles.