2012

I NEED to have this on some page dedicated to innovative games
The game is very good about giving each mechanic / experience its 'appropriate' amount of time, and then switching to something else.
Determining what the 'appropriate' amount of time is for a particular mechanic / experience is a very interesting question. That YT channel I'm binging on talks a lot about AAA games forcing players to spend WAY too much time with a particular mechanic / experience.
The music is quite good.
The game is very, very good at surprising you.
The game violates gameplay conventions.
When you're shooting at the bugs, you can just swim down and totally avoid them, going into an underwater area instead.
The apples fall down 'into the water', which in a normal game would mean they're gone forever, but you can just swim down and pick them up.

2016

The thoughts below are based on watching this: Doom - Ultra Nightmare
- it isn't a speedrun, but the guy seems to know what he's doing, so he doesn't waste time either.

It seems to be doing what all the other sci-fi shooters do, which is to try to look realistic and somewhat interesting rather than trying to look as interesting as possible, and not care much at all about the realism. It's tough because Doom 1 wasn't graphically realistic in the way that DOOM is, and so it's tricky to try to think of a way to continue the tradition of very-interesting level design while not looking ridiculous.
The color and space-fillers seem very trope-like: it's all metal/gray, with pipes going everywhere, and metal walking platforms.
They use the trope of some loud person speaking from a loudspeaker, the way Portal 1/2 did. They don't use it for narrative stuff the way Portal 1/2 did, but even just saying "Access Granted" is something that doesn't actually happen in r/l, it's a TV/movie/videogame trope.
Ex: 15:40
There's a lot of jumping around, jumping from one platform to another, jumping up onto something or down onto something. That seemed more like a Quake thing to me, although obviously it's nowhere near Quake in terms of speed.

They have a lot of slow-moving zombie-like humans at the beginning of the game. But zombies and demons are kind of different genres (Resident Evil blurs the line, but AFAIK RE's 'evil' creatures are a result of genetic experiments by humans and not actually demons from hell). They're definitely similar genres (horror, violent, disfigured human-like creatures). The original Doom 1 manual refers to the human enemies in the game as "Former Humans", while the source code refers to them as "MT_POSSESSED". It looks like they be frequently refered to as "zombiemen" in the Doom community. In any case, the main issue I have is with the Doom16 possessed scientists following the trope of zombie-like shuffling around.

At least in the first 15 minutes it seems like the dominant strategy is to use your gun to stun an enemy while closing in on it, and then 1-shot the enemy with your melee attack. It's kind of ridiculous how OP your melee is. The chainsaw is actually substantially slower than just meleeing everyone.
Ex: at 16:30 the guy literally just goes to like 5-7 guys and melees them instead of shooting them.
Having the demons using blue see-through shields is a little Halo-y for me.
Ex: 45:30

They have constant "Hold X to open the grate" messages that pop up and break immersion. Another popular thing to do nowadays. I guess it helps the less-familiar players, but it shouldn't be showing up on "Ultra Nightmare" difficulty.
There's just a lot of stuff that pops up on the screen and IMO breaks immersion. My "crazy" idea would be: If the guy is wearing a helmet with an integrated UI, have the helmet simulated / visible, with a *slight* distortion to simulate the fact that the guy has some kind of see-through material in front of his eyes, and maybe some small parts of the helmet visible in the corner of the screen.

It has the standard thing where you'll have some dude talking for a while, and then the takeaway is you need to travel down some hallways and maybe press a button, so you don't actually need to listen to anything the guy is saying. Ex at 22:10. IDK, personally I find these things really take me out of the vibe / tension that the game should be trying to create. My favorite parts of OFP were the parts with no dialog, where the gameplay and environment combined to create a ton of tension, or a feeling of peacefulness.
Female villain - 41:00 They always refer to her by her first name, "Olivia". IDK, I find it stupid. It's like talking about Charles Manson as "Charles".

Totally standard Sci-Fi shooter music. Nothing at all distinguishing about it. Unlike the original Doom, with its metal focus.
They do switch to metal during a particularly action-packed sequence (40:00).

It has kind-of stupid flourishes, like having your character punch the upgrade-bots when you've decided what upgrade you want from them. 15:00
It's broken into levels like the original Doom, which would allow for speedruns / par times, but then it has all of this