TL;DR: This is basically a rogue-lite version of Heretic (remember that old classic?). I strongly approve.

Game's really smooth, -- at least, as smooth as you'd allow a rogue-like (or rather rogue-lite) to be at all. Graphics and the game engine itself are pretty good. Some (most, actually) of the monster animations are really simpistic, but that's not a bad thing, really (you don't expect a rogue-like to have state-of-art graphics, do you?). Most possibly, this is a first first-person rogue-lite out there too, by the way.

Gameplay is really simple: you're opening door after door on a floor, killing monsters, gathering loot (new spells/weapons, new items), leveling up (and getting 1 of 2 perks each level -- Crimsonland much?). In order to transfer to the next level, you must kill the boss. In order to do that, you must locate: a) an exit (or a boss room, if you like); b) token to open it. Each floor is procedurally generated -- monsters, spells, rooms and settings are randomized. This means, every time you're starting over, you're getting a new map to explore.

By dying you'll lose your progress, but as of what I've seen, there's a total of 5 levels in the dungeon, so the game's main feature is starting it over and over again -- unlocking new classes, new weapons, new items and filling the lore book with new pages -- and getting basically a new experience every time.

If you're a fan of rogue-likes, or if you ever played games like Hexen and Heretic, this game certainly is a "must play".

I'd rate this game 8.5 out of 10.0.