| 6.6. Going, Pushing Things in Directions |
It is very common for players to make a mistake and type the wrong direction command, or even to misunderstand the room description and not recognize all the possible exits. Bumping into Walls helpfully adds a facility so that when the player tries to go in the wrong direction, the game lists the correct possibilities, as in
From here, the viable exits are to the south, the east and the west.
Another useful technique is to provide some sense of the journey between locations, especially if they are remote from one another or the player has to do something unusual to get from one to the other. Up and Up adds a short description of travel when we approach a new room, before the room description is printed; Veronica, conversely, adds a comment when the player leaves a region of the map. The Second Oldest Problem intervenes and kills a player who tries to travel from one dark room to another. Mattress King embellishes the description that automatically results from PUSH MATTRESS WEST, adding a line that describes the player pushing the object before describing the new room approached.
We may also want to add a brief comment when we arrive in a new room, after the room description is printed. One trivial way to do this is to append the line to the room's main description, conditionally, like this:
The Hammock Emporium is a room. "This is Cousin Ed's shop, the big dream he left accounting to pursue. You can't help gawking at the Luxury Leather Space Hammock, made of genuine red buffalo skins[if unvisited]. [paragraph break]So this is why Grampa makes all those 'lying down on the job' jokes every Thanksgiving[end if].".
But often we want our first-glance comment to come after some items in the room are described; and for this effect, we would use the "first look rule" defined in Saint Eligius.
Another category of examples treat how we handle the movement commands themselves. The eight compass directions, with UP and DOWN, IN and OUT, are used as standard in most interactive fiction, but they are not the only possible way of navigating, and strike many newcomers to the genre as counter-intuitive, since when strolling around in real life most of us rarely think about our travel in terms of compass orientation. Misadventure allows the player to GO TO a named room, instead, and calculates the best route to reach the destination; Safari Guide builds on this by letting the player make the whole trip in a single move, automatically opening any doors that stand in his way en route.
We also sometimes want to respond sensibly to terse movement commands or ones that rely on some knowledge of where the player has already been. Polarity provides a GO BACK command, allowing the player to retreat in the direction from which he came, while Minimal Movement understands LEAVE, GO, and so on as OUT, in the absence of other information. Owen's Law takes this further, calculating from the best routes on a map how to make OUT mean "move towards the exit of this indoor room", and IN mean "proceed further into the interior". Wonderland assigns altitudes to all rooms and works out the local best meaning of UP and DOWN accordingly.
Indirection renames the compass directions to correspond to primary colors, as in Mayan thinking. A similar technique is useful for shipboard travel.
See Ships, Trains and Elevators for ship-board directions
See Bicycles, Cars and Boats for common vehicles in which to travel the map
|  Example Up and Up Adding a short message as the player approaches a room, before the room description itself appears. | |
| Example Veronica An effect that occurs only when the player leaves a region entirely. | |
Text in this example is drawn from Will Crowther's original 1976 FORTRAN implementation of ADVENTURE, the founding work of the genre, whose source code was rediscovered by Dennis R. Jerz in 2007. Note the capitals: the program ran on an early computer without lower case lettering. They look a little mimsy now, but picture them glowing green on an old-style cathode ray tube monitor in a darkened room late at night.
The problem alluded to is that the player is forbidden to walk between two dark rooms, so that he must always have light to see by from at least one end of any movement. Writing source text to achieve this is tricky to get right in every case, because the determination of light is hard to do. Here we interleave the necessary rules into the existing "going" action, using a new action variable to record the number of ends which are dark as experienced by the player, which might be 0, 1 or 2:
"THE SECOND OLDEST PROBLEM"
The going action has a number called the dark terminus count.
Setting action variables for going:
now the dark terminus count is 0;
if in darkness, increase the dark terminus count by 1.
The last carry out going rule:
if in darkness, increase the dark terminus count by 1;
if the dark terminus count is 2, end the game saying "YOU FELL INTO A PIT AND BROKE EVERY BONE IN YOUR BODY!" instead.
And now three early rooms to try this out.
COBBLE CRAWL is a room. "YOU ARE CRAWLING OVER COBBLES IN A LOW PASSAGE. THERE IS A DIM LIGHT AT THE EAST END OF THE PASSAGE."
DEBRIS ROOM is west of COBBLE CRAWL. "YOU ARE IN A DEBRIS ROOM, FILLED WITH STUFF WASHED IN FROM THE SURFACE. A LOW WIDE PASSAGE WITH COBBLES BECOMES PLUGGED WITH MUD AND DEBRIS HERE,BUT AN AWKWARD CANYON LEADS UPWARD AND WEST."
AWKWARD CANYON is west of DEBRIS ROOM. "YOU ARE IN AN AWKWARD SLOPING EAST/WEST CANYON."
DEBRIS ROOM and AWKWARD CANYON are dark.
Rule for printing the name of a dark room: say "DARKNESS" instead.
Rule for printing the description of a dark room: say "IT IS NOW PITCH BLACK. IF YOU PROCEED YOU WILL LIKELY FALL INTO A PIT." instead.
Test me with "w / e / w / w".
This is only the second oldest problem in the IF literature: the earliest puzzle is unlocking the steel grate which bars entrance to the cave.
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| Example Saint Eligius Adding a first look rule that comments on locations when we visit them for the first time, inserting text after objects are listed but before any "every turn" rules might occur. | |
| Example Misadventure A going by name command which does respect movement rules, and accepts names of rooms as commands. | |
|  Example Safari Guide The same functionality, but making the player continue to move until he reaches his destination or a barrier, handling all openable doors on the way. | |
| Example Minimal Movement Supplying a default direction for "go", so that "leave", "go", etc., are always interpreted as "out". | |
|  Example Wonderland Hiking Mount Rainier, with attention to which locations are higher and which lower than the present location. | |
| Example Indirection Renaming the directions of the compass so that "white" corresponds to north, "red" to east, "yellow" to south, and "black" to west. | |