"The inventory system is another way of communicating to the player. One of the first things you do, playing Interactive Fiction, is to check what the character is carrying. In our little imaginary game, Bilbo starts out with a pipe, tobacco, matches, and nothing else. This might as well be a road flare: after looking around a bit and maybe trying to take the doorknob, the door, and the Hill, most players will naturally try to smoke the pipe. They can’t expect it to summon the wizard (or more accurately, to trigger subroutine GANDALF|SMOKE), but they can fairly expect it to do something. After all, why else would it be possible to carry it? Note again the possibility for confusing the player, either unintentionally or sadistically. What if the player starts with a whole knapsack full of gewgaws, only one of which is useful? Or what if it is possible to take the doorknob? The poor sap will surely never put it down again. “There must be a use for this doorknob,” the player thinks, as they dodge Orcs beneath the Misty Mountains. “Any day now with the doorknob,” they think, as they stab spiders in Mirkwood. “Please oh please don’t let me drop my doorknob!” they moan, as they cling to the barrel on the River Running. And then — oh God, those poor fools — when they’re on the Lonely Mountain, and they run into a door for the first time since the start of the game, they will immediately fixate on the idea that they’ve finally figured out what the doorknob is good for, and obsessively try to figure out a way to attach it to the cliff face so that they can pull it open (not that that makes any sense), ignoring the thrush until it dies of old age."