If you still thought portal was in any way a technical innovation, its amazing how easy it is to implement in the source engine. I'm sure you've seen the gmod one, this goes a step futher.
http://www.stridermod.com/
Created 18 years ago2006-08-24 06:03:12 UTC by Jobabob
The portal LUA stuff comes with the map?Yeah, it comes with all the swep stuff zipped inside the rar.