I wasn't kidding when I said that I prefer playing the original Doom 2 over Doom Eternal. I initially started with the GOG version, known as Doom 2 Enhanced. It added some modern conveniences like horizontal mouse look and autorun, but not much else. Later, I decided to give the original Doom 2 a try with GZDoom. This version provided full mouselook and the ability to jump, which made finding secrets easier. In the original Doom, you had to attempt awkward run-jumps to access certain areas, which could be challenging even with WASD controls. Imagine how much more difficult it was with arrow keys.
My favorite levels so far have to be "Dead Simple" and "Tricks and Traps." I think "Tricks and Traps" is one of my all-time favorite levels, thanks to its clever hub design.

Speaking of level names, when I first played Doom, my English skills were quite limited. Even something as simple as "Downtown" was a bit confusing for me.
Surprisingly, I still remember all the secrets up to this point, completing every level with a 100% score. But I must say, Refueling Base, with its 18 secrets, can be infuriating. Seriously, Refueling Base, you're not making it easy!
Oddly enough, I can't blame the game for being too difficult. I expected to be constantly saving and loading, but I rarely find the need to do that.
There are a few no-escape pits here and there, like the final room in "Tricks and Traps." And in "Factory," you're teleported right into the middle of an imp cluster.
In "Inmost Dens," it's puzzling that they simply forgot to count secrets as secrets. There are still secret walls and all, but the number of secrets on that level is listed as 0.
Speaking of secrets, I'm still going strong and even found the secret and the super-secret Wolfenstein levels.
"Citadel" has this abstract art vibe to it. It's not that the Doom Engine couldn't handle something resembling the real world; the creators of Doom 2 just didn't want that.

"Gotcha," the level where you face off against a Cyberdemon and a giant spider at the same time, almost "got me" with its super hard-to-find last secret. Turned out it was a hidden door near one of the teleporters in the winding tower.

Following "Nirvana" felt like someone didn't have enough time to finish it properly. There are no secrets on that level, and you can literally pass through blue bars without the blue key.
I remembered that the "Monster Condo" level had some kind of crazy secret, and it actually does! There's a room that's open only for the first 30 seconds of the level.
It's interesting how in the pre-final level, Living End, you can just run past the final Cyberdemon once you know where to aim. That, and the mouselook, make it easier.

Speaking of mouselook, it's easy to see how much better I am now compared to when I struggled with this game as a kid. But it's essential to remember that, with GZDoom, the game looks like this now:

As a kid, the game looked like this:

And I was playing it on a crappy monitor, so it was even more blurry, dark, and distorted. Plus, I didn't know about the Doom engine's limitations, like the lack of rooms above rooms. And there was no mouselook, of course. Just arrow keys, and strafing was on Alt.
Oh, and by the way, I never noticed that those Revenant missiles would chase you indefinitely: