New sign model asset, soundscape ambience stuff.

Remade two barrel props due to improper collisions.

Gmpublisher freaked out and made this addon a copy of the map addon, this has been fixed.

Added one music track, and includes remade models for some of the propper brushes.

Small change.

Re-added previously removed skybox materials because somebody did not listen to me, twice, sorry for the wasted space.

i also added in ambience for future soundscape use, might re-sort it a little bit to make Xen underground areas feel more alive.

Minor asset fixes, Xen lightstalks no longer get their whole model fully colored due to the differences between how Source and GoldSource handles color on models.

Updated one texture.

Added one prop and its materials.

Added developer tool texture custom made by me for soundscape use.