Hetzchase Nailway is my upcoming map pack to be used in Valve's Portal as a Bonus Map though the map series should be slightly longer than the game's original single player campaign and posses a LOT more replay-ability.
I released an alpha several months ago which can still be downloaded here:
This video showcases some elements of the maps' progress. It's still a long way from being completed, but I wanted to at least let you all know I haven't stopped working on it. So far it features everything from Co-Op levels with NPCs to timed chambers that are music-based.
The lead goal of this map pack is to allow the player to experience synæsthesia. Most testers report a strong psychological sense of nostalgia, so I think I'm getting close.
If you are interested in contributing to this project please feel free to contact me on steam: