Mention early first-person perspective 3D games to someone and they’re most likely to picture a “gridder” — the projection of a 2D map into a fake 3D perspective, through which you move by “step”, one cell at a time.
The reason for this is that it was the easiest way to create a 3D effect without actually having to do any real “3D” — hell, one of the earliest and most famous examples of this was on the humble ZX81 in the form of 3D Monster Maze. And indeed this style of presentation (if not necessarily the exact execution) remains popular today for many first-person perspective dungeon crawlers from both Eastern and Western developers, allowing for intricate, interesting level design without the need for complex 3D modelling.
Some talented coders in the early 8-bit era figured out ways to get more natural movement through these “projected 2D” maps, allowing you to rotate through angles other than 90 degrees and move relatively freely. One such example on the Atari 8-bit was 1982’s technically impressive Way Out (sometimes stylised as Wayout). The creator of this game, one Paul Allen Edelstein, remains part of the games industry to this day, albeit now with a specialism in video and audio compression technology rather than 3D graphics.