Old Doom VS Retail Doom
What's interesting to me is how the levels have changed quite a bit, some levels are completely different and are much bigger!
Some rooms in the final version of Doom used to be secret rooms, so it's interesting to see how things have changed during the development process.
Here are some shots comparing the old version to the final version.
As you can see, the room is completely gone... Or so you'd think!
The same room is behind the armor as a secret room leading to a shotgun, in the final version the secret room is no longer a secret and the armor has replaced the shotgun.
The next room looks nothing like the final version, pretty boring with almost no details heh.
The last room I'm going to show is pretty similar but notice the Imp "fireball" it's some sort of weird star in the old version.
Overall the final version looks a lot better and polished, more detail and such, but it's still very interesting to see the old stuff, especially the later levels as they are much bigger and include stuff that you won't see in the final version of Doom.
You can have a look at the video yourself, the Doom gameplay doesn't start till about 09:30 so fast forward if that's all you're interested in.
YouTube Link


