Feels like downport of Doom 2016, which isn’t a bad thing. Imps are just a carbon copy, but other enemies are pretty similar as well: zombies, shotgun zombies, flying round demons that shoot fireballs, bulls-demons that run at you. Arsenal is pretty standard: pistol, double SMGs, minigun. The only slight surprise is that a shotgun can be charged, and that the plasma rifle can “latch” to a target once you land your first shot.
Each level contains multiple ore fragments. And as far as I can tell, some weapons can only be purchased with these. Also, each level contains multiple checkpoints, but if you quit it in the middle, you’ll have to replay it from the beginning. Luckily, those are pretty short: 15 minutes on average.
Although enemies are 2D, the authors did something very smart and rendered them from the top as well, in different perspectives. When you look at them from they top, their sprites aren’t distorted, like in Ion Maiden.