Yo, that was really fun! I haven't played many games in this retro doom style but I actually enjoyed it a lot.
The difficulty ramp up did feel steep but also very satisfying, specially for the last boss. Took me quite some time to figure out the strat specially on the shocking ground (and it may be way too easy to get cornered in that phase), but it felt really cool once I got through it.
The environment looks quite neat and exploration was definitely consistent, I almost felt it would be a bit annoying figuring my way out sometimes but I did do it fairly quickly, so point on that. Atmosphere was conveyed very well, specially on the rooms with dead corpses, and the ambience fit perfectly.
I think my only complaint would be the font, like a few other people mentioned already. It was bearable to read the in-game instructions but the intro was just impossible to understand, specially given the varying interval of which each line stayed on screen which didn't always seem to match the line's length (or maybe I just got that impression due to taking so long to read and not being able to get some of the letters at all).
Overall, great game!