Minor spoilers are not indicated. If you want the full experience, play it first.
Every so often you come across a mod that really chimes with you, and Courage comes very close to doing so. Described by its creator 'turboluigi' (this is why I love the mod community) as "L4D2 meets Dear Esther", it dabbles with the former's gameplay while taking just a few pages from the latter's surrealism.
What results is a technically competent and incredibly dark piece that creates a much more resounding sense of finality than any conventional death sequence I've played in some time. Naturally, only a short singleplayer mod could pull off this kind of thing, and I gave the whole thing two run-throughs in around ten minutes or so.
Built in the Source engine, there are no major tweaks to note - the guns go bang and the bad men fall down. The conventional linearity of most Half-Life 2 mods is replaced with a single open area, which within moments is swamped with zombies. Your running gun battle allows you to grab ammunition and health, while the generously proportioned map gives you plenty of breathing space without suffering from the problems of having the shambling necrotics become a shooting gallery.
The real hook of the mod lies in 'courage', a virtual reality system that opens up to the player after eliminating the resident zombie population. Half-Life mods suffer greatly from a weapon and physics set that's ten years old, and without the resources to code in new guns increasingly clever ideas are a necessity. Once activated, courage shunts you to an alternate reality in a thoroughly jarring tonal shift that left me on the right side of bemused without being inappropriate.
Thematically, Courage absolutely nails it. The humour is subtle and the tone well-balanced. There's a sharp irony to the real world's advertisements for courage, and the facile world of the simulation is set against a grim and invasive reality. Without spoiling it, I thoroughly recommend playing the mod twice to understand the mechanics involved; the twist has frightening implications that really make you think about the implications of your actions. I'm probably going to do a writeup of that in the coming days.
On a more critical slant, I personally found some of the music in the courage sequences to border on the overly sentimental, and I think the contrast between the real and simulated worlds is sufficiently jarring without a crooning vocalist. SPOILERS I found the 'good' ending a little weak as well, and again overly optimistic for my personal taste. Like Danny Boyle's film Sunshine, this might have been one instance where the happy ending could have been replaced by an endless, one-man holdout against an onslaught. Equally, it provides firm closure and an acceptable reward for persevering, so each to their own. SPOILERS OVER.
Overall, it's very much a short-and-sweet piece that for its download size is well worth the entry fee of zero pounds/dollars/euros/whatever. While it borders the line between dull, routine, silly and manipulative, Courage very much does so in all the right ways. Thoroughly recommended.