This is an amazing game. It takes the aesthetic and pacing of the original Doom/Quake and heavily improves upon it. The art style really brings the whole thing to a new level of retro gore-horror and that coupled with the amazing and fluid gameplay make this one of the best games I've played in the past few years.
If I had to critique one thing, I'd say that the slide and groundpound don't get nearly enough use. They are introduced and then used for a few puzzles and then that's it. My idea for a better groundpound would be that it does damage in a radius and not just on a direct hit. It would also be cool if the damage of a groundpound scaled based on how high up the player was at the start of the groundpound.
Still, this is an amazing game, and I will definitely buy the full game once it comes out.