When the player types a command at the keyboard - say, EAST - it is translated into an action: in this case, "going east". There are more than a hundred basic actions built into Inform, and almost all works of IF involve creating new ones to add to the stock. Each action is caused by a variety of possible commands, and subject to various rules to check their viability.

The Actions index aims to give a clear picture of how each action can happen, and what rules apply to it. (It's useful to know the names of Inform's rules, so that we can waive or change them in special circumstances.)

For instance, we see below that the commands CLOSE DOOR and CLOSE UP DOOR would both result in the action "closing the door", which would then be subject to two rules checking it for realism: if we try to close a closed door, for instance, the "can't close what's already closed rule" will kick in.

We picture the possibly long lists of commands as being like long threads with knots at one-inch intervals. The Skein braids these together. Here there are two different threads: one from a game in which the player typed INVENTORY (asking to see what he is carrying), then dropped the manuscript and tried to leave Paternoster-Row; and another in which he went into Longman's, then took an INVENTORY and then tried to physically hand over the book.

These two threads differ right from the start, so they hang down as independent lines from the top "start" knot. The two different initial commands are in amber because the game currently playing in the Game panel is poised at the start position, waiting for us to choose which thread we shall follow - or, of course, to type something entirely different and begin a new thread.

The "Go to label..." drop-down menu is a rapid navigation tool for finding our way around what can eventually be a large and complicated Skein.