Games like Duke 3D were designed to be fully playable without any mouse, though. It was deactivated by default, the combat was rarely out of the horizontal (and if it wasn't, there was vertical auto aim) and the game never really required you to properly look up or down except for finding secrets.
Until Quake and its true three-dimensional approach game struggled with height, anyway.
Descent or terminal velocity were the first vertical shooters I've seen.
Not sure about heretic or hexen, but I think strife had vertical at the time.
Duke needed that functionality because jetpack flight, and it became a requirement for deathmatch.
Because you can frag much faster with mouse aim than key scroll, arrow movement went extinct.
Heretic (and subsequently Hexen) also had vertical functionality. The basic Doom engine has some issues with rendering room-over-room situations, but there were some ways to get around that.
I think Marathon was one of the first FPS games that had proper free mouselook from the start.
Descent, as the name implies, was obviously a strongly mouse-bound vertical shooter, but it was also a background title few were really familiar with. Even
Hexen was a somewhat unknown title in those days, despite the fact that it would later earn a (deservedly so) strong cult following. Most shooters were eclipsed by
Doom (for many years) and
Duke Nukem 3D. Even
Quake was overshadowed until its sequel, and even then the biggest following those games received were their mods and speedruns, both of which were smaller, niche communities.
Doom and
Duke Nukem 3D were the top dogs of the shooter genre for many, many, many years.
Doom didn't have any issues with layering rooms on top one another; it was straight up IMPOSSIBLE. The engine was really 2.5D as there was no way to interact with the z-axis outside of falling and rising, which was little more than an illusion because your character was simply continuing on along the horizontal axises. You couldn't drop *on top of* an enemy, because their unit took up the entire z-axis. If there was a floor, or an object, or an enemy, that was the defined z-axis in totality.
Duke 3D improved upon these shortcomings by some workarounds, but they were finicky. You could "interact" with sprites that could "levitate" you above a floor on an artificial floor, and this was done in abundance with catwalks, so the game was able to pull off the illusion of overlapping levels, but they were used very sparsely because of how unreliable they were. The game largely resorted to cleverly hidden "teleports" where one level would SEEM to be above another, when in reality you'd teleported to another section a long distance away on the x/y-axises.
Hexen (not
Heretic, which was a
Doom clone with the sole exception of adding an item system) was not nearly as advanced as
Duke 3D, and had the same limitations of the z-axis as
Doom did, but the level designs were far grander, and made much more use of height, despite the fact that the *player* couldn't interact with them.
Quake was the first game to actually develop true 3D and utilize it in a shooter without any technical limitations to the z-axis, and as mentioned above, despite being a technically superior title, it was still overshadowed by Duke's popularity for a long time.
Quake was the first title where using the mouse was actually practical, but it still used the legacy "auto targeting" shots which would train their targets along the z-axis so long as you were lined up with them on the horizontal axises, and this was done so the much more popular keyboard controls (which didn't make frequent use of looking up or down, due to how out-of-the-way the buttons were to where your hands rested) could function ideally with the game.
Mouses didn't become the norm for player control in shooters until well into the early 00s, and it was only through popularization by mods like
Counter Strike. It was totally unapparent that WASD could be used for movement, because *everyone* was completely accustomed to using the arrow keys with your right hand for movement, so the notion of relegating movement to keys that weren't arrows, and for your left hand, was VERY far outside the box, which is why it took so long to catch on.
And, as I stated, which began this epoch of discussion on the history of shooters and their controls,
Shadow Warrior was a title that fell well within the middle of this transitionary period. It was a spiritual successor to
Duke 3D, yet it was an obscure title that few knew much about. It functioned almost identically to
Duke 3D, with a few small improvements, and it still used the legacy auto-targeted vertical shots with the option to look up and down that was very infrequently used because the buttons were out-of-the-way of the customary button layout. The mouse controls were there, but they simply went unused, and they didn't function AT ALL like how mouses presently work in modern FPS games. Meanwhile, the
Shadow Warrior Classic Steam Game has modern FPS controls coded into it, which is the ONLY "update" added into the game, so it feels wonky and unresponsive, at times, since the game wasn't designed with these control schemes in mind.
When using the remote control cars/boats, they become unruly because the normal "turn" controls have been shifted to the mouse, so you have to constantly drag your mouse back and forth to get very little turn out of the thing you're controlling, whereas back in 97 this worked very well because of the default arrow keys. The newer version has the auto-targeting disabled, which makes targeting enemies quite difficult compared to how it used to be, due to the abundance of floating or ducking or leaping enemies, so you chew through your ammo in the Steam version, unlike in the original, just to kill basic enemies. The changes to the controls and the mechanics aren't very large, but their impact on the game is felt cumulatively as you go along, and they really add up to major adverse affects in the long run. I don't know how much this applies to
Redux, but it's quite likely to have a similar impact, since it's still working with the same engine, in the end.
All told, it's still a great game, and I'm still enjoying playing it. It's just that right now, on Steam, it's a great game with newer controls that clash with the game's design, so it presents hiccups where there weren't any, originally. Kinda like how the higher FPS made
Shadow of the Colossus HD FAR trickier than the original. I'm not gonna stop playing SW right now, but that doesn't mean I don't notice the changes for the worse.
