Thief: The Dark Project

Thief's ideas spread widely once it succeeded. Splinter Cell's light meter came from Thief, Mark of the Ninja turned Thief into a side scroller, and Dishonored is a near spiritual successor that even reuses Garrett's voice actor.

Thief arrived in November 1998, after Tenchu in August and Metal Gear Solid in October; the three set the genre's core rules.

Mark of the Ninja showed Thief's hidden state to turn stealth into planning. Mark of the Ninja, by Nels Anderson, added UI showing light and shadow, how far sounds travel, what guards see and think, and what items will do. Where Thief is about patient observation and immersion, this makes Mark of the Ninja about building plans, luring guards and setting traps.

Quote: "By showing the player exactly how the world works, the player feels powerful and capable."

Thief built its tension on a submarine simulator's power dynamic. Designer Ken Levine took the core feel from Silent Service: a submarine can strike unseen with torpedoes but panics when destroyers find it, because it cannot fight them toe to toe.

Levine described this as the opposite of what shooters were doing. In Thief you can try to fight, but you will likely die, so you use the blackjack. Quote: "How powerful you are when you are unseen, and how weak you are when you are spotted."

Non-lethal play on higher difficulties turned restraint into the challenge. On higher difficulties Thief forbids killing guards, so finishing a mission becomes a test of staying unseen rather than of combat.

Mark of the Ninja later used the same idea as a rewarded choice rather than a hard rule.

Open, interconnected levels let players pick their own route to the prize. Thief's missions usually set a goal like a sword, sceptre or jewel in the innermost part of a guarded mansion, with several pathways toward it and no single right one.

The game often leaves it to the player to decide how much of the mansion to cross. Hitman and Dishonored share this design.

Water and moss arrows let players change the level's rules. Water arrows put out candles to create darkness and moss arrows lay down silent tiles, so the player reshapes the space instead of only reacting to it.

Noisemaker arrows and deliberate noise let players lure guards into traps. Changing the environment like this is rare in the genre; Splinter Cell's shoot-out-the-lights option is one of the few other examples.

The Light Gem tells players exactly how visible they are. Thief's Light Gem shows how exposed you are to sight, solving the same problem as Tenchu's Ki Meter and Metal Gear Solid's Soliton radar: it removes guesswork so the player can plan a route.

Quote: "it removes the ambiguity of whether or not you're about to be spotted".

Guards shout their state aloud, so danger is heard in the world. Thief supplements the Light Gem with guards who call out when they notice something suspicious, communicating the AI's state without extra UI.

Quote: "guards are extremely vocal about their current state as they will shout out".

Floor materials make sound as important as sight. Soft leaves are quiet but running on hard tiled floors alerts guards, so players read the floor as well as the guards.

Quote: "think carefully about the materials you're walking on".

Unaware guards and a suspicious middle state make stealth forgiving. Missions start with guards who know nothing of the player, and the goal is to keep it that way. Guards investigate odd sights and sounds before attacking and give up the hunt if you hide, so a small mistake does not trigger a full alert.

Thief shares these rules with Tenchu and Metal Gear Solid, the other two stealth games of 1998. Resetting to neutral spares the player from reloading a save or killing everyone.

Thief's ambitious guard AI was broken until the last few months. The guard AI and sound propagation were revolutionary for the time, and so advanced that the game was a buggy mess until late in development.

Quote: "the guard AI was so advanced that it was a broken, buggy mess up until the last few months of development".

CD quality audio made Thief's sound-based stealth possible. Thief needed CD quality audio and advanced guard AI, part of the 3D and CD technology wave of the late 1990s that made games about hiding from enemies workable.

Thief's ideas spread widely once it succeeded. Splinter Cell's light meter came from Thief, Mark of the Ninja turned Thief into a side scroller, and Dishonored is a near spiritual successor that even reuses Garrett's voice actor.

Thief arrived in November 1998, after Tenchu in August and Metal Gear Solid in October; the three set the genre's core rules.

Popularising a mechanic matters more for influence than inventing it. Metal Gear 2 already had a radar, loud metal grates, suspicious guards, wall knocking and a reset to neutral, but it ran only on the MSX2 in Japan, so Looking Glass likely never played it. Thief drew on Silent Service instead.

Metal Gear Solid and Thief got the credit, just as Doom did for the first-person shooter. Quote: "the game that popularised a genre or mechanic wasn't the one to actually invent it".