>>2876740
The third and the fourth things are, actually, well, again closely connected. The third is, well, I mentioned before that Petersen's levels require you to "get it" before you can progress relatively painlessly. That is actually a general rule and the main mark of his levels. They, the big parts of them, are designed specifically, so that to break the "flow", to make you stop, and to think, and to make you devise the way to progress. That aforementioned "brush of bars" moment from E4M2, that impossible jump in E4M8, the way infighting is utilized in E4M6 and the way you lure the spawns into the underwater traps, which allows you to kill them off just via lobbing a couple of grenades into that trap, the way traps in E4M5 are rigged and the way you deduce how to access the secret level from that E4M5 level, etc. The fourth thing, closely connected to the third, is that notifications to the player are utilized very actively, even telling you about weapons you forgot on the level, and giving you hints on what that particular button opened.
What I think all the aforementioned four things tie into, is... Well, actually, I think that looks suspiciously like gnosticism (and I don't care if that's in any way connected to Petersen being a Mormon). Like, escaping from the illusory material reality which only causes suffering through Knowledge/Revelation. Like, that's what I make of what I experienced in Q1's E4.
I may be right or I may be wrong concerning my speculations, but, the main point I think, is that ep4 is a very interesting and unusual experience, which is very much a thing of its own, which is the pinnacle of Petersen's FPS work, and... And, frankly, I can't remember anything which struck quite the same chord with me in all the FPS genre (well, that part of it I'm acquainted with anyway).
So, yeah, that was my attempt at explaining just why I consider ep4 being any good.