The 14 advanced chambers from the XBLA version of Portal, now playable on your PC!
This is the whole mod. It includes the 14 challenge chambers as well as the original TFV Mappack.
To install, extract the folder 'Portal-StillAlive' to this directory:
C:\Program Files (x86)\Steam\steamapps\sourcemods\
Or, where ever your Steam installation is, then \steamapps\sourcemods\
Then, restart Steam. It will appear in your Steam Games list as "Portal: Still Alive"