Late last year, Crowbar Collective released the first screenshot of the Xen area of its Half-Life remake Black Mesa, which was not included with its original release. The team said that it was focused on "crafting a fun and cohesive experience from start to finish," and that it wanted to "push the boundaries and explore this unique and varied setting." The plan at the time was to have Xen out this summer; unfortunately, getting it right is taking longer than expected.
"As some of you may have already predicted, we are going to need to push back our planned release of Xen to later this year, in December. We know that this is not what anyone would want to hear, but after taking a long and hard look at what we want to achieve, we have decided that this is for the best. We do not want to compromise on Xen’s quality in any way," the studio wrote on Steam. "That said, we consider December to be a do-or-die deadline."
To soften the blow, Crowbar posted the first two public images of a Xen exterior, and also provided more information about what exactly it's doing with the level. A new dynamic lighting system for use in situations "where we want the lights to be particularly gorgeous" has been implemented, a "color correction pass" on the entire game is underway, and enemy soldiers will now hold their weapons properly, without their hands clipping through their guns.
Crowbar didn't get into the specifics of the delay, but if I had to (or just wanted to) hazard a guess, I'd say it's probably at least in part because the original Xen level was awful: A dull, utterly un-fun area that was completely out of sync with the rest of the game. A fresh coat of paint is enough for most of Half Life, but making Xen itself "fun and cohesive" is a whole different ballgame.