What does a level designer actually do?
Designs the spaces players move through and what happens in them — which is a discipline of pacing, communication and psychology far more than of decoration. The visual appearance is usually someone else's job.
The distinction that matters. A level designer determines layout, flow, encounter placement, pacing and the sequence of player experience. A level artist or environment artist makes it look like a place. On smaller teams one person does both; on large ones they are separate roles with separate skills.
What the work actually involves:
Blocking out the space in simple geometry — grey boxes, no art — and playing it repeatedly. Almost all of the design work happens at this stage, before anything looks like anything, because it is cheap to change.
Guiding the player without instructions. Using light, colour, sightlines, contrast, landmarks, sound and movement to draw attention — so players go the intended way while feeling they chose it. This is the core craft.
Pacing. Alternating tension and release, dense and open, combat and quiet. A relentless sequence exhausts players; an unbroken calm bores them.
Encounter design, placing enemies, cover and objectives so a fight has a shape rather than being a room with occupants.
Teaching mechanics through play, introducing an idea safely, then complicating it, then testing it — without a tutorial screen.
Readability, ensuring players can tell what is traversable, interactive, dangerous or scenery. Breaking this rule is the fastest way to make a space frustrating.
Accommodating failure, including checkpoints and recovery.
The techniques with names: the critical path and optional branches; landmarking for orientation; affordances signalling what can be done; breadcrumbing; and gating progress until something is learned.
Why iteration dominates. Designers watch people play, silently, and observe where they hesitate, get lost, or miss the obvious. What players do differs from what they say, which is why observation outranks feedback.