A "DOOM clone" in the truest sense, but a very, very good one. The all-new art and assets are quite polished and the feel is fresh enough despite being on its progenitor's engine. It's more than just a reskin, too -- they got pretty ambitious with an inventory system full of items that transform the gameplay. The implementation is shaky and the items themselves are hit-and-miss, but a couple of them (like the one that powers up all of your weapons into totally different forms for a limited time) are quite fun and useful.

Most impressive of all, to me, was the level design, which does a great job of suggesting larger structures and organic areas with DOOM's limited tools, but also deftly avoids falling into that series' trap of abstract mazes and annoying switch puzzles. The flow of each area is very well designed and signposted in a way to guide the player organically without being too obvious about it. Top-tier work for this period.

I was very surprised by how good this is. I can see myself coming back to it.