Chocolate Doom is basically the state of the art for playing Doom exactly vanilla-style, with the low 320×200 resolution and all.
GZDoom should be more preferable for "normal" people that care less about every bit of game mechanic minutiae and just want a high-resolution game. (Only caveat is that it defaults to a blurred display... need to find and change that to nearest filtering)
The original Doom had "auto aim" - all you had to do was match an enemy's column and the hit would connect - because you were not able to look up and down in the original game.
In GZDoom, you can enable freelook+mouselook, enabling 360 degrees of looking, and gameplay is balanced IMHO by disabling auto aim, requiring you to aim accurately. For extra challenge I like to disable the crosshairs. To me, most of the original levels are really not easier with this configuration so I don't feel like I'm losing the essence of the original Doom with this too much.
You can also use the awesome Brutal Doom mod to enhance the gameplay - it does add lots of gory effects but gameplaywise it also gives the enemies additional attacks and makes flammable stuff a dangerous thing in the game.
Also you can get GZDoom down to 320x200 resolution if you want, and it doesn't set the video mode on the latest versions so no dependency on your graphics card to support ancient hardware resolutions.
Ostensibly not true :) Even in the vanilla engine, Z axis calculations are used everywhere (one of the most obvious visual effects is when fireballs and rockets fly over your head).
"Doom is 2D" is an urban legend dating to the 1990s that badly needs to die. It is not and has never really been true, and should be even more obvious after its open source release.
I clearly remember (but not in which game) a tight room with ledges on each side where you basically shoot blind horizontally to hit enemies out of screen above.
All depends on what part of the game you consider:
Level geometry is indeed 2D (or rather 2D projectable without intersection, hence the 2.5D moniker)
Gameplay though, is 3D, and actually hampered by not being able to look up down, which for shooting was compensated by vertical auto-aim. There are many places where it's hard to see the enemies above or below, or even where you're going to go/navigate. Luckily the level design is usually nicely done and usually caters for that with enough room space to kinda see things and/or elevators but there are a couple of areas that can be especially tricky or frustrating.
> maybe this limitations turns into the explanation that its 2d?
But it still not 2D. These types of engines are referred as 2.5D since ancient times specifically because they aren't full 3D but they aren't 2D either.
> You can't look up and down either, so your shots go twords the enemies hieght.
This is a limitation of implementation. Duke3D, built on the exactly same principles, allows you look around, and ROTT too.
> but I remeber some discussion of a restrictions where can't have a room directly above another room
> where you can can go over and under (like a bridge).
You can't have a proper 3D bridge, but you can place a sprite and walk over it, this technique is used by a later DOOM engine mods, Duke3D, ROTT [0]
RoR isn't that difficult to implement in a 2.5D engine, you just need to keep track in which one the entities are located (and Z axis helps here a lot).
Overall, all that 2D/2.5D/3D bickering is pointless if you understand what while DOOM, Duke3D, ROTT engines are 3D, their map layout (specifically the map geometry, not the entities) is 2D only, though with an additional 'ceiling height' and 'floor height' property per sector hence 2.5D.
The world geometry is defined in a limited 3D fashion (but still 3D since while the walls are defined in a 2D plane, there is also sector floor and ceiling heights which add the third dimension - a modern equivalent would be terrain that is almost always a heightmap that can't create caves etc - these are done with additional geometry and clever hiding of the seams by the artists) but the objects are placed in three dimensions.
However some calculations only take into account the two dimensions, e.g. object-to-object collision is often done on the XY plane, hence you can be "blocked" by enemies or pillars or other objects that are "below" or "above" you.
This is probably a terribly silly question, but, to do this do I just buy DOOM2 on steam -> https://store.steampowered.com/app/2300/DOOM_II/ find the doom2.wad _somewhere_ and then run it as above?
And one more possibly even sillier question, on steam on OSX can you even download the files (because it's only available on windows platform?)
