Official Quakewiki Video - Quake - Aftershock for Quake - GLASS

Based on the appearance of the level, I am pretty sure that this is another level from the QuakeLab. A quick Google search even has a level somewhat similar to this (though it seems somewhat different as well) which confirms a few details about the Glass.

The reason I feel this is a QuakeLab level is because of the light fixtures. They look exactly the same as the ones in Exploding Wall. We also have a square like room with the new feature straight ahead and a weapon nearby the player's starting location. Oddly enough, this level doesn't have a name beyond the filename.

This level is a little less interesting than the aforementioned Exploding Wall. Both are basically hacks of the original game materials to create new obstacles. Still, at least the Exploding Wall was a bit more interactive, this has little more to do than look at a wall of Glass.

There are 2 Enemies in this map, but neither can be killed (there is a possible way to kill them when using explosives, but as there are no Rocket Launchers or Grenade Launchers here that is somewhat impossible without cheats).

Though the word "Glass" implies a transparent material, which this is, it usually also implies a very fragile material. This Glass is not fragile, possibly because no animation in the game would be appropriate and therefore the Glass would simply just disappear. The reason the Glass must be an entity is to ensure that the Enemies can get alerted to the player's presence (something that wouldn't happen with a transparent wall).

The Glass has 99999999999999999 health points. Shub-Niggurath had 40000 and took a good deal of time to kill in versions prior to its fix in 1.06. You might need to waste an entire afternoon shooting rockets at the Glass for it to eventually be destroyed. Nobody wants to watch me hit a Glass wall for a day (remember, it would take even longer as we only have an Axe) to kill two Enemies. I don't even have that kind of patience to do this when I am not recording.

According to the Readme I mentioned earlier, the mechanics of the Glass wall, and the time it would take I think it is pretty fair to say that those two Enemies are intended to be impossible to kill.

This level definitely shows off a new feature, though it is pretty boring as it is little more than a transparent wall. There is no interactivity involved, the level actually is designed in a way to prohibit such actions. The lack of texturing also means that it is pretty dull, real life glass usually has some sort of tint. This does not feel so much like glass as an invisible barrier, something which tends to be disliked by gamers and is a rather dull element which is done due to engine limitations.