I have this clear memory of playing the first Thief, crouching against the wall in a dark stairwell as a guard walked closer. I held my breath until he passed, hidden in a shadow inches away. The games in the original Thief trilogy were all about light and darkness, with a “light gem” at the bottom of the screen to indicate whether you were really in the dark, reducing the guesswork created by the oddities of first-person bodies and your own screen settings. It’s an obvious idea more stealth games should borrow.
A a lot of things from the original Thief games didn’t become standard in the genre, and even the 2014 reboot/sequel didn’t pick up on some of them. For that we have The Dark Mod [official site].