==================== Captain Fate: take 1 ==================== .. epigraph:: | *S was a sailor, and spent all he got;* | *T was a tinker, and mended a pot.* .. only:: html .. image:: /images/picS.png :align: left .. raw:: latex \dropcap{s} imple though they are, our two games have covered most of the basic functionality of Inform, providing enough solid ground underfoot for you to start creating simple stories. Even if some of what you've encountered doesn't make sense yet, you should be able to browse a game's source code and form a general understanding of what is going on. We'll now design a third game, to show you a few additional features and give you some more sample code to analyse. In "Heidi" we tried to make progress step by step, explaining every bit of code that went into the game as we laid the objects sequentially; in "William Tell" you'll have noticed that we took a few necessary explanatory detours, as the concepts grew more interesting and complicated. Here we'll organise the information in logical didactic chunks, defining some of the objects minimally at first and then adding complexity as need arises. Again, this means that you won't be able to compile for testing purposes after the addition of every code snippet, so, if you're typing in the game as you read, you’ll need to check the advice in "Compile-as-you-go" on page 255. A lot of what goes into this game we have already seen; you may deduce from this that the game design business is fairly repetitious and that most games are, when you reach the programming bottom line, another remake of the same old theme. Well, yes and no: you've got a camera and have seen some short home videos in the making, but it’s a long way from here to Casablanca. To stick with the analogy, we'll now construct the opening sequence of an indie B-movie, a tribute to the style of super-hero made famous by a childhood of comic books: .. pull-quote:: "Impersonating mild mannered John Covarth, assistant help boy at an Impersonating insignificant drugstore, you suddenly STOP when your acute hearing deciphers a stray radio call from the POLICE. There’s some MADMAN attacking the population in Granary Park! You must change into your Captain FATE costume fast...!" which won't be so easy to do. In this short example, players will win when they manage to change into their super-hero costume and fly away to meet the foe. The confrontation will -- perhaps -- take place in some other game, where we can but hope that Captain Fate will vanquish the forces of evil, thanks to his mysterious (and here unspecified) superpowers. Fade up on: a nondescript city street ===================================== The game starts with meek John Covarth walking down the street. We set up the game as usual: .. code-block:: inform6 !% -SD !============================================================================ Constant Story "Captain Fate"; Constant Headline "^A simple Inform example ^by Roger Firth and Sonja Kesserich.^"; Release 3; Serial "040804"; ! for keeping track of public releases Constant MANUAL_PRONOUNS; Constant MAX_SCORE 2; Constant OBJECT_SCORE 1; Constant ROOM_SCORE 1; Include "Parser"; Include "VerbLib"; !============================================================================ ! Object classes Class Room with description "UNDER CONSTRUCTION", has light; Class Appliance with before [; Take,Pull,Push,PushDir: "Even though your SCULPTED adamantine muscles are up to the task, you don't favour property damage."; ], has scenery; !============================================================================ ! The game objects Room street "On the street" with name 'city' 'buildings' 'skyscrapers' 'shops' 'apartments' 'cars', description "On one side -- which your HEIGHTENED sense of direction indicates is NORTH -- there's an open cafe now serving lunch. To the south, you can see a phone booth."; !============================================================================ ! The player's possessions !============================================================================ ! Entry point routines [ Initialise; location = street; lookmode = 2; "^^Impersonating mild mannered John Covarth, assistant help boy at an insignificant drugstore, you suddenly STOP when your acute hearing deciphers a stray radio call from the POLICE. There's some MADMAN attacking the population in Granary Park! You must change into your Captain FATE costume fast...!^^"; ]; !============================================================================ ! Standard and extended grammar Include "Grammar"; !============================================================================ Almost everything is familar, apart from a few details: .. code-block:: inform6 Constant MANUAL_PRONOUNS; Constant MAX_SCORE 2; Constant OBJECT_SCORE 1; Constant ROOM_SCORE 1; By default, Inform uses a system of automatic pronouns: as the player character moves into a room, the library assigns pronouns like IT and HIM to likely objects (if you play "Heidi" or "William Tell" and type PRONOUNS, you can see how the settings change). There is another option. If we declare the ``MANUAL_PRONOUNS`` onstant, we force the library to assign pronouns to objects only as the player mentions them (that is, IT will be unassigned until the player types, say, EXAMINE TREE, at which point, IT becomes the TREE ). The behaviour of pronoun assignment is a matter of personal taste; no system is objectively perfect. Apart from the constant ``MAX_SCORE`` that we have seen in "William Tell", which defines the maximum number of points to be scored, we now see two more constants: ``OBJECT_SCORE`` and ``ROOM_SCORE``. There are several scoring systems predefined in Inform. In "William Tell" we've seen how you can manually add (or subtract) points by changing the value of the variable ``score``. Another approach is to award points to players on the first occasion that they (a) enter a particular room, or (b) pick up a particular object. To define that a room or object is indeed “particular”, all you have to do is give it the attribute ``scored``; the library take cares of the rest. The predefined scores are five points for finally reached rooms and four points for wondrous acquisition of objects. With the constants ``OBJECT_SCORE`` and ``ROOM_SCORE`` we can change those defaults; for the sake of example, we've decided to modestly award one point for each. By the way, the use of an equals sign ``=`` is optional with ``Constant``; these two lines have identical effect: .. code-block:: inform6 Constant ROOM_SCORE 1; Constant ROOM_SCORE = 1; Another difference has to do with a special short-hand method that Inform provides for displaying strings of text. Until now, we have shown you: .. code-block:: inform6 print "And now for something completely different...^"; return true; ... print_ret "And now for something completely different..."; Both lines do the same thing: they display the quoted string, output a newline character, and return true. As you have seen in the previous example games, this happens quite a lot, so there is a yet shorter way of achieving the same result: .. code-block:: inform6 "And now for something completely different..."; That is, *in a routine* (where the compiler is expecting to find a collection of statements each terminated by a semicolon), a string in double quotes by itself, without the need for any explicit keywords, works exactly as if there were a ``print_ret`` in front of it. Remember that this way of displaying text implies a ``return true`` at the end (which therefore exits from the routine immediately). This detail becomes important if we *don't* want to return true after the string has been displayed on the screen -- we should use the explicit ``print`` statement instead. You'll notice that -- unusually for a room -- our ``street`` object has a ``name`` property: .. code-block:: inform6 Room street "On the street" with name 'city' 'buildings' 'skyscrapers' 'shops' 'apartments' 'cars', ... Rooms aren't normally referenced by name, so this may seem odd. In fact, we're illustrating a feature of Inform: the ability to define dictionary words as "known but irrelevant" in this location. If the player types EXAMINE CITY here, the interpreter will reply "That's not something you need to refer to in order to SAVE the day", rather than the misleading "You can't see any such thing". We mostly prefer to deal with such scenic words using classes like ``Prop`` and ``Furniture``, but sometimes a room's ``name`` property is a quick and convenient solution. In this game, we provide a class named ``Appliance`` to take care of furniture and unmovable objects. You’ll notice that the starting room we have defined has no connections yet. The description mentions a phone booth and a café, so we might want to code those. While the café will be a normal room, it would seem logical that the phone booth is actually a big box on the sidewalk; therefore we define a ``container`` set in the street, which players may enter: .. code-block:: inform6 Appliance booth "phone booth" street with name 'old' 'red' 'picturesque' 'phone' 'booth' 'cabin' 'telephone' 'box', description "It's one of the old picturesque models, a red cabin with room for one caller.", before [; Open: "The booth is already open."; Close: "There's no way to close this booth."; ], after [; Enter: "With implausible celerity, you dive inside the phone booth."; ], has enterable container open; What's interesting are the attributes at the end of the definition. You'll recall from Heidi's ``nest`` object that a ``container`` is an object capable of having other objects placed in it. If we make something ``enterable``, players count as one of those objects, so that they may squeeze inside. Finally, ``containers`` are, by default, supposed to be closed. You can make them ``openable`` if you wish players to be able to OPEN and CLOSE them at will, but this doesn't seem appropriate behaviour for a public cabin -- it would become tedious to have to type OPEN BOOTH and CLOSE BOOTH when these actions provide nothing special -- so we add instead the attribute ``open`` (as we did with the nest), telling the interpreter that the container is open from the word go. Players aren't aware of our design, of course; they may indeed try to OPEN and CLOSE the booth, so we trap those actions in a ``before`` property which just tells them that these are not relevant options. The ``after`` property gives a customised message to override the library’s default for commands like ENTER BOOTH or GO INSIDE BOOTH. Since in the street's description we have told players that the phone booth is to the south, they might also try typing SOUTH. We must intercept this attempt and redirect it (while we're at it, we add a connection to the as-yet-undefined café room and a default message for the movement which is not allowed): .. code-block:: inform6 Room street "On the street" with name city' 'buildings' 'skyscrapers' 'shops' 'apartments' 'cars', description "On one side -- which your HEIGHTENED sense of direction indicates is NORTH -- there's an open cafe now serving lunch. To the south, you can see a phone booth.", n_to cafe, s_to [; <>; ], cant_go "No time now for exploring! You'll move much faster in your Captain FATE costume."; .. todo:: Notice how the syntax coloring thinks that the exclaimation point above is a comment. This is another problem with the built-in inform6 syntax colorer. That takes care of entering the booth. But what about leaving it? Players may type EXIT or OUT while they are inside an enterable container and the interpreter will oblige but, again, they might type NORTH. This is a problem, since we are actually in the street (albeit inside the booth) and to the north we have the café. We may provide for this condition in the room's ``before`` property: .. code-block:: inform6 before [; Go: if (player in booth && noun == n_obj) <>; ], Since we are outdoors and the booth provides a shelter, it's not impossible that a player may try just IN, which is a perfectly valid connection. However, that would be an ambiguous command, for it could also refer to the café, so we express our bafflement and force the player to try something else: .. code-block:: inform6 n_to cafe, s_to [; <>; ], in_to "But which way?", Now everything seems to be fine, except for a tiny detail. We've said that, while in the booth, the player character’s location is still the ``street`` room, regardless of being inside a ``container``; if players chanced to type LOOK, they'd get: .. code-block:: transcript On the street (in the phone booth) On one side -- which your HEIGHTENED sense of direction indicates is NORTH -- there's an open cafe now serving lunch. To the south, you can see a phone booth. Hardly an adequate description while *inside* the booth. There are several ways to fix the problem, depending on the result you wish to achieve. The library provides a property called ``inside_description`` which you can utilise with enterable containers. It works pretty much like the normal ``description`` property, but it gets printed only when the player is inside the container. The library makes use of this property in a very clever way, because for every LOOK action it checks whether we can see outside the container: if the container has the ``transparent`` attribute set, or if it happens to be ``open``, the library displays the normal ``description`` of the room first and then the ``inside_description`` of the container. If the library decides we can’t see outside the container, only the inside_description is displayed. Take for instance the following (simplified) example: .. code-block:: inform6 Room stage "On stage" with description "The stage is filled with David Copperfield's magical contraptions.", ... Object magic_box "magic box" stage with description "A big elongated box decorated with silver stars, where scantily clad ladies make a disappearing act.", inside_description "The inside panels of the magic box are covered with black velvet. There is a tiny switch by your right foot.", ... has container openable enterable light; Now, the player would be able to OPEN BOX and ENTER BOX. A player who tried a LOOK would get: .. code-block:: transcript On stage (in the magic box) The stage is filled with David Copperfield's magical contraptions. The inside panels of the magic box are covered with black velvet. There is a tiny switch by your right foot. If now the player closes the box and LOOKs: .. code-block:: transcript On stage (in the magic box) The inside panels of the magic box are covered with black velvet. There is a tiny switch by your right foot. In our case, however, we don't wish the description of the street to be displayed at all (even if a caller is supposedly able to see the street while inside a booth). The problem is that we have made the booth an ``open`` container, so the street's description would be displayed every time. There is another solution. We can make the ``description`` property of the ``street`` room a bit more complex, and change its value: instead of a string, we write an embedded routine. Here's the (almost) finished room: .. code-block:: inform6 Room street "On the street" with name 'city' 'buildings' 'skyscrapers' 'shops' 'apartments' 'cars', description [; if (player in booth) "From this VANTAGE point, you are rewarded with a broad view of the sidewalk and the entrance to Benny's cafe."; else "On one side -- which your HEIGHTENED sense of direction indicates is NORTH -- there's an open cafe now serving lunch. To the south, you can see a phone booth."; ], before [; Go: if (player in booth && noun == n_obj) <>; ], n_to cafe, s_to [; <>; ], in_to "But which way?", cant_go "No time now for exploring! You'll move much faster in your Captain FATE costume."; The description while inside the booth mentions the sidewalk, which might invite the player to EXAMINE it. No problem: .. code-block:: inform6 Appliance "sidewalk" street with name sidewalk' 'pavement' 'street', article "the", description "You make a quick surveillance of the sidewalk and discover much to your surprise that it looks JUST like any other sidewalk in the CITY!"; Unfortunately, both descriptions also mention the café, which will be a room and therefore not, from the outside, an examinable object. The player may enter it and will get whatever description we code as the result of a LOOK action (which will have to do with the way the café looks from the *inside*); but while we are on the street we need something else to describe it: .. code-block:: inform6 Appliance outside_of_cafe "Benny's cafe" street with name 'benny^s' 'cafe' 'entrance', description "The town's favourite for a quick snack, Benny's cafe has a 50's ROCKETSHIP look.", before [; Enter: print "With an impressive mixture of hurry and nonchalance you step into the open cafe.^"; PlayerTo(cafe); return true; ], has enterable proper; .. todo:: Figure out how to set off this entire note section as an indented block NOTE : although the text of our guide calls Benny's establishment a "café" -- note the acute "e" -- the game itself simplifies this to "cafe". We do this for clarity, not because Inform doesn't support accented characters. The *Inform Designer's Manual* explains in detail how to display these characters in "§1.11 *How text is printed*" and provides the whole Z-machine character set in Table 2. In our case, we could have displayed this:: The town's favourite for a quick snack, Benny's café has a 50's ROCKETSHIP look. by defining the ``description`` property as any of these: .. code-block:: inform6 description "The town's favourite for a quick snack, Benny's caf@'e has a 50's ROCKETSHIP look.", description "The town's favourite for a quick snack, Benny's caf@@170 has a 50's ROCKETSHIP look.", description "The town's favourite for a quick snack, Benny's caf@{E9} has a 50's ROCKETSHIP look.", However, all three forms are harder to read than the vanilla "cafe", so we've opted for the simple life. .. todo:: Indented block ends here Unlike the sidewalk object, we offer more than a mere description. Since the player may try ENTER CAFE as a reasonable way of access -- which would have confused the interpreter immensely -- we take the opportunity of making this object also ``enterable``, and we cheat a little. The attribute ``enterable`` has permitted the verb ENTER to be applied to this object, but this is not a ``container``; we want the player to be sent into the *real* café room instead. The ``before`` property handles this, intercepting the action, displaying a message and teleporting the player into the café. We ``return true`` to inform the interpreter that we have taken care of the ``Enter`` action ourselves, so it can stop right there. As a final detail, note that we now have two ways of going into the café: the ``n_to`` property of the ``street`` room and the ``Enter`` action of the ``outside_of_cafe`` object. A perfectionist might point out that it would be neater to handle the actual movement of the player in just one place of our code, because this helps clarity. To achieve this, we redirect the street's ``n_to`` property thus: .. code-block:: inform6 n_to [; <>; ], You may think that this is unnecessary madness, but a word to the wise: in a large game, you want action handling going on just in one place when possible, because it will help you to keep track of where things are a-happening if something goes *ploof* (as, believe us, it will; see "Debugging your game" on page 197). You don't need to be a perfectionist, just cautious. A booth in this kind of situation is an open invitation for the player to step inside and try to change into Captain Fate's costume. We won't let this happen -- the player isn't Clark Kent, after all; later we'll explain how we forbid this action -- and that will force the player to go inside the café, looking for a discreet place to disrobe; but first, let''s freeze John Covarth outside Benny''s and reflect about a fundamental truth. A hero is not an ordinary person ================================ Which is to say, normal actions won't be the same for him. As you have probably inferred from the previous chapters, some of the library’s standard defined actions are less important than others in making the game advance towards one of its conclusions. The library defines PRAY and SING, for instance, which are of little consequence in a normal gaming situation; each displays an all-purpose message, sufficiently non-committal, and that's it. Of course, if your game includes a magic portal that will reveal itself only if the player lets rip with a snatch of Wagner, you may intercept the ``Sing`` action in a ``before`` property and alter its default, pretty useless behaviour. If not, it's "Your singing is abominable" for you. All actions, useful or not, have a stock of messages associated with them (the messages are held in the ``english.h`` library file and listed in Appendix 4 of the *Inform Designer's Manual*). We have already seen one way of altering the player character's description -- "As good looking as ever" -- in "William Tell", but the other defaults may also be redefined to suit your tastes and circumstantial needs. John Covarth, aka Captain Fate, could happily settle for most of these default messages, but we deem it worthwhile to give him some customised responses. If nothing else, this adds to the general atmosphere, a nicety that many players regard as important. For this mission, we make use of the ``LibraryMessages`` object. .. code-block:: inform6 Include "Parser"; Object LibraryMessages ! must be defined between Parser and VerbLib with before [; Buy: "Petty commerce interests you only on COUNTED occasions."; Dig: "Your keen senses detect NOTHING underground worth your immediate attention."; Pray: "You won't need to bother almighty DIVINITIES to save the day."; Sing: "Alas! That is not one of your many superpowers."; Sleep: "A hero is ALWAYS on the watch."; Strong: "An unlikely vocabulary for a HERO like you."; Swim: "You quickly turn all your ATTENTION towards locating a suitable place to EXERCISE your superior strokes, but alas! you find none."; Miscellany: if (lm_n == 19) if (clothes has worn) "In your secret identity's outfit, you manage most efficaciously to look like a two-cent loser, a good-for-nothing wimp."; else "Now that you are wearing your costume, you project the image of power UNBOUND, of ballooned, multicoloured MUSCLE, of DASHING yet MODEST chic."; if (lm_n == 38) "That's not a verb you need to SUCCESSFULLY save the day."; if (lm_n == 39) "That's not something you need to refer to in order to SAVE the day."; ]; Include "VerbLib"; If you provide it, the ``LibraryMessages`` object must be defined *between* the inclusion of ``Parser`` and ``VerbLib`` (it won't work otherwise and you’ll get a compiler error). The object contains a single property -- ``before`` -- which intercepts display of the default messages that you want to change. An attempt to SING, for example, will now result in "Alas! That is not one of your many superpowers" being displayed. In addition to such verb-specific responses, the library defines other messages not directly associated with an action, like the default response when a verb is unrecognised, or if you refer to an object which is not in scope, or indeed many other things. Most of these messages can be accessed through the ``Miscellany entry``, which has a numbered list of responses. The variable ``lm_n`` holds the current value of the number of the message to be displayed, so you can change the default with a test like this: .. code-block:: inform6 if (lm_n == 39) "That's not something you need to refer to in order to SAVE the day."; .. todo:: That block of code above should be colored. Is there a defect in the syntax coloring code? where 39 is the number for the standard message "That's not something you need to refer to in the course of this game" -- displayed when the player mentions a noun which is listed in a room's name property, as we did for the ``street``. .. todo:: Begin big chunk of indented text. Also, NOTE should be in bigcaps. NOTE : remember that when we are testing for different values of the same variable, we can also use the switch statement. For the Miscellany entry, the following code would work just as nicely: .. code-block:: inform6 ... Miscellany: switch (lm_n) { 19: if (clothes has worn) "In your secret identity's outfit, you manage most efficaciously to look like a two-cent loser, a good-for-nothing wimp."; else "Now that you are wearing your costume, you project the image of power UNBOUND, of ballooned, multicoloured MUSCLE, of DASHING yet MODEST chic."; 38: "That's not a verb you need to SUCCESSFULLY save the day."; 39: "That's not something you need to refer to in order to SAVE the day."; } .. todo:: End big indented chunk Not surprisingly, the default message for self-examination: "As good looking as ever" is a ``Miscellany`` entry -- it's number 19 -- so we can change it through the ``LibraryMessages`` object instead of, as before, assigning a new string to the ``player.description property``. In our game, the description of the player character has two states: with street clothes as John Covarth and with the super-hero outfit as Captain Fate; hence the ``if (clothes has worn)`` clause. This discussion of changing our hero's appearance shows that there are different ways of achieving the same result, which is a common situation while designing a game. Problems may be approached from different angles; why use one technique and not another? Usually, the context tips the balance in favour of one solution, though it might happen that you opt for the not-so-hot approach for some overriding reason. Don't feel discouraged; choices like this become more common (and easier) as your experience grows. .. todo:: Begin big indented chunk. That "whatever new look" needs to be italicized. NOTE: going back to our example, an alternative approach would be to set the variable ``player.description`` in the ``Initialise`` routine (as we did with "William Tell") to the "ordinary clothes" string, and then later change it as the need arises. It is a variable, after all, and you can alter its value with another statement like ``player.description = *whatever new look*`` anywhere in your code. This alternative solution might be better if we intended changing the description of the player many times through the game. Since we plan to have only two states, the ``LibraryMessages`` approach will do just fine. .. todo:: End big indented chunk A final warning: as we explained when extending the standard verb grammars, you *could* edit the appropriate library file and change all the default messages, but that wouldn't be a sound practice, because your library file will probably not be right for the next game. Use of the ``LibraryMessages`` object is strongly advised. If you're typing in the game, you'll probably want to read the brief section on "Compile-as-you-go" on page 255 prior to performing a test compile. Once everything's correct, it’s time that our hero entered that enticing café.