Thief

Thief treats level space as something players trade in and reshape. Designer Greg LoPiccolo describes space as the commodity players deal in, split along axes like light and shadow and loud and quiet. Water arrows douse candles to turn lit danger into shadow, and moss arrows make floors quiet, so the level is something to change rather than a fixed puzzle.

The framing behind it: "a stealth game level is like a sea of danger, and you've got to swim between the islands of safety."

Thief keeps water arrows scarce by charging stolen money for them. Players pay for water arrows with loot stolen in earlier stages, so each one is a choice about when to spend it rather than a default answer to every lit room.

"A rather obvious way to restrict something's power is just to limit how many you have."

Thief's light gem shows a value first-person players can't judge. A gem at the bottom of the screen shows how visible the player currently is, because in first person it is hard to tell how lit you are.

Turning a hidden value into a readout replaces guesswork with information the player can act on.

Thief aimed to keep players on the cusp of being found. Programmer Tom Leonard wanted to hold players right at the edge of detection to get their hearts pounding, using uncertainty about whether they are safe.

This suits the fragile power of the stealth fantasy, where the player is never fully in control.

Thief's guards share second-hand information to seem intelligent. Guards can know about the player from what other enemies are up to, not only from what they see or hear themselves.

Awareness beyond the player gives designers hooks for traps and distractions and "can also help give the impression of intelligence and awareness."

Realistic layouts let players guess where the loot is. In Lord Bafford's Mansion the gold sits in the lord's chambers and little of value is in the servants' quarters, so real-world knowledge tells players where to search.

Architecture, layout and scale show who uses a space, which both tells a story and helps players orient themselves.

Garrett's role as a thief decides how players solve problems. The Looking Glass philosophy was about embodying a character in a realistic world and tackling problems in ways that made sense for him. Garrett has no superpowers and direct attacks are discouraged, so stealth and burglary are the tools.

The immersive sim genre later moved to the Deus Ex formula with bionic powers and now treats Thief's character-first approach as a failed experiment along the way.