Thread:Vorknkx/@comment-3547390-20150204202730/@comment-1496755-20150327200642

Well, well, I guess the same map designers participated in more than one project. It's not very surprising - I get the impression that there was a group of guys who thought "monotonous single-texture maps are awesome" and decided to develop several mission packs revolving around this concept. It's good that the main Aftershock episodes were not affected by this.

It may seem that all authorized third-party products were horrible back in those days, but luckily there are some exceptions here and there. The most notable among them is Blood's Cryptic Passage - a third-party mission pack that some fans (myself included) consider to be superior to the game's official mission pack, especially in terms of level design.

These products seem to have been quite popular, particularly in the mid/late 1990's. Nowadays this phenomenon is dead. I haven't heard of any commercial third-party map pack for any of the modern games.