Doom shipped in December 1993 and it was not actually 3D. John Carmack built a raycasting engine that faked depth using 2D sprites on angled walls. Every monster, pickup, and projectile was a flat sprite rotating to face the player. Freelancers working on retro-style indie games today still recreate this exact technique deliberately, because the aesthetic carries weight.
The constraint was the point. Artists had 256-colour palettes and sprites measured in pixels, not polygons. The Baron of Hell, one of Doom's toughest enemies, used eight directional sprite frames to simulate movement in 3D space. Eight frames. That discipline around asset economy is something modern freelance artists often underestimate when scoping indie contracts.
By 1996, Quake replaced the sprite system with fully polygonal models. Quake's Grunt soldier used roughly 150 polygons total. For comparison, a character in a mid-budget 2024 mobile game typically runs between 8,000 and 15,000 polygons. That jump happened across about 28 years, and each milestone redefined what studios expected from contracted artists.
If you freelance in game art, knowing this history helps you read a client brief accurately. When a studio says they want a Doom-era aesthetic, they mean sprite discipline and palette limits, not just pixel art filters. Specificity in your references signals that you understand the technical history, not just the visual surface.