Xen

Introduction

Xen, or the "borderworld", is an alien dimension accessible through high levels of energy channeled within teleportation devices. It is revealed in Half-Life that Black Mesa scientists sent expedition teams into Xen to collect alien samples, most notably the orange crystal that triggers the disaster. Half-Life ends with the player travelling to Xen and defeating the Nihilanth.

Architecture

Xen consists mostly of organic, spongelike platforms floating in a nebulous void. Various energy sprires, sphincters, and other organic growths are relatively commonplace. Deep inside some or the larger "asteroids" would be extensive cavern systems, rivers, and resevoirs. The gravity in Xen is relatively lower then the rest of the Half-Life world.

Xen was often criticised for its frustrating "jumping puzzles" - jumping from platform to platform, or jumping off of giant manta-rays, etc. Therefore, it is best to relegate moving platforms to an atmospheric role rather than a gameplay mechanic.

Environment

Being an alien dimension, Xen lighting was often very bright and saturated. Crystals and bioluminscent "tubelights" would provide neon lighting in most Xen levels, generally being the only source of lighting aside from a sun-like entity in the distance.

Obviously, a Xen level should feel alien. However, mods such as Point Of View have proven that man-made architecture can be integrated with Xen, if done properly.

NPCs

Xen is the native home of various organisms such as the headcrab, the barnacle, and the vortigaunt (aka Alien Slave). No humans are present except dead expedition members, which creates a desolate feeling for the player and evokes heroic tones, similar to the Citadel.

In general, no human or humanoid enemies should be seen in a Xen level. This would include both Combine soldiers as well as zombies.