Well... It seems like your time is come again, Mr Freeman.
This mod is an attempt at an arena-styled game play, focused on the player facing against a single opponent per small arena. I was confused by the title at first, but the mod's folder name is called "duel", which leads me to that conclusion.
This mod is very short, and very easy given the context, but the brushwork is really nice in each set piece. The game on a whole is one level long, which is fine, but even then it's incredibly jarring how short it is, especially given the type of game it's trying to be.
I understand this was made during a game jam, then later finalized. This probably explains the shortness of the mod overall. I do like the addition of power-ups in the level design, but I think it would have been finer with using regular health kits and armor packs instead, mostly because they weren't really utilized in my play-through until I discovered them after the fact.
It's hard to say that this is worth your download time, but it's a small download, and once you've got it set up, it's alright. I would have liked to have seen more difficult fights with the earlier enemies.
tl;dr
Some enemies simply aren't designed to face one-on-one in the half-life universe, and by that I mean that the mod is too easy.