Games::ScottAdams::Manual - The Scott Adams Adventure Compiler Reference Manual
# foo.sa - definition file for Scott Adams adventure "foo"
%exit n meadow
%exit e edge
%exit w grove
Evil smelling mud
%action take mud
msg BOY that really hit the spot!
The Scott Adams compiler, sac, allows you create adventure games in a straightforward syntax, and compiles them into the format that was used in the classic Scott Adams adventures - and which is therefore now understood by scottfree and various other interpreters for those old games.
If you're running a Linux system, there's a fair chance that you already have such an interpreter on your system - it's probably called scottfree, ScottCurses, GnomeScott or something similar. Certainly Red Hat Linux distributions from 4.0 onwards (and maybe much earlier) have come with Scott Adams interpreters.
This manual describes the syntax of the sac file which sac compiles into Scott Adams format.
All of the examples are taken from Scott Adams' first game, the classic Adventureland - a game dripping with atmosphere and nostalgia which I can't recommend highly enough.
Comments may appear anywhere in a sac file, and have no effect on the compiled adventure. They are introduced by a hash character (#) and extend to the end of the line.
Completely blank lines (and those which are completely blank after comments have been removed) may appear anywhere in the file, and have no effect on the compiled adventure.
All data is introduced by a directive - that is, a line which begins with a percent sign (%) immediately followed by a word specifying which directive is being used. Common examples include %room, %exit, %item and %action. Directive names are case-insensitive, so that %room, %ROOM, %Room and indeed %rOoM all mean the same thing.
We describe the directives in four categories, corresponding to the four fundamental concepts in Scott Adams adventures: the rooms through which the player moves, the items found in those rooms, the actions which the player can perform, and global parameters.
With one exception, the order in which directives and their associated data appear is not significant. This yields important flexibility in how the adventure definition file is laid out: for example, all the rooms may appear together followed by the items, or each room may be followed by the items which appear in it; items not initially in play may be listed first or all, or at the end, or after the rooms in which they will be brought into being during the game.
The one exception to this order-independence is that the order in which actions appear is significant, because on each turn, each possible action is considered in the order that appear. Ordering issues are discussed in more detail in the section about the %action directive, but in summary: while the order of actions relative to other actions is in some cases significant, the position of actions relative to rooms, items and global parameters is not. Actions may be moved ahead of and behind rooms, items and global parameters with impunity.
The first fundamental concept of Scott Adams adventures is the rooms: a connnected network of nodes between which the player can move using the four primary compass directions plus Up and Down. With typical topography, after moving north from one room to another, it's possible to move south back to the first room - but the system does not enforce this, making it possible to create complex mazes.
Each room in a sac file is identified by a unique name - typically short, and made up of alphanumerics, possibly with underscores, although the only restriction enforced is that it may not contain any whitespace characters (space, tab, etc.)
Apart from its name, a room is defined by a description and a set of available exits, each exit specifying its destination room.
root chamber under the stump
Creates a new room whose name is the word immediately after the %room directive, on the same line. The following lines, up to but not including the next line that contains a directive, make up the description of this room, which is what the player sees. (The name, by contrast, is used only by sac itself, as an identifying tag when the room must be referred to when defining an exit, item or action.)
For historical reasons, Scott Adams interpreters such as scottfree emit the string ``I'm in a '' (or ``You're in a '', if the appropriate option is specified) before room descriptions, so that the room defined above would be described as
I'm in a root chamber under the stump
When this behaviour is not desired, it can be overridden by beginning the room description with an asterisk (*), which is not printed but inhibits the automatic initial string. For example, the room definition
*I'm on a narrow ledge by a chasm. Across the chasm is
is described to the player simply as
I'm on a narrow ledge by a chasm. Across the chasm is
%exit u stump
Specifies that it's possible to move from the most recently defined room in the direction indicated by the first argument, and that doing so takes the player to the destination indicated by the second argument. Rooms may have any number of exits from zero to all six.
The first argument to the %room directive must be one of the single letters n, s, e, w, u or d (or their upper-case equivalents), indicating exits in the directions north, south, east, west, up and down respectively.
The second argument must be the name of a room defined somewhere in the sac file. The destination room's definition may be either previous or subsequent - forward references are just fine.
It's OK for an exit to lead back to the room it came from, and for more than one exit to lead in the same direction, as in the following example:
%exit n forest
%exit s forest
%exit e meadow
%exit w forest
The second fundamental concept of Scott Adams adventures is the items: things that reside in a room, and in some cases can be picked up, carried around and left in other rooms. Typically, some of the items are ``objects'' like axes and keys, while others are ``scenery'' like trees, signs, etc.
As with rooms, each item in a sac file is identified by a unique name - typically a short, alphanumeric-plus-underscores name. Because the concepts of room and item are so distinct in the Scott Adams model, it's OK for a room and an item to share the same name. In fact this is often the obvious thing to do - for example, consider a situtation where the player can see a tunnel, then type ENTER TUNNEL to move inside the tunnel. In this case, it's natural for both the tunnel item and the tunnel room to have the name tunnel.
Apart from its name, an item is defined by its location and possibly by a ``getdrop'' name - see below.
*Pot of RUBIES*
Creates a new item whose name is the word immediately after the %item directive, on the same line. The following line is the description of this item, which is what the player sees. (The name is used only as an identifying tag.)
Should we allow multi-line object descriptions by reading up to but not including the next directive line as with room descriptions?
If the item name begins with an asterisk (*) then it is considered to be a treasure: it, along with any other treasures, must be deposited in the treasury (see below) in order to win the game. The asterisk is displayed to the user; traditionally, another asterisk appears at the end of treasure descriptions, but this is not enforced.
By default, each item starts the game in the last room defined before its %item directive; this means that sequences like the following do The Right Thing:
*I'm on the shore of a lake
However, in some cases, it may be convenient to define items at some other point in a sac file - for example, some authors may prefer to list all rooms together, then all items together. In such cases, an item may be relocated to its correct starting room by providing a %at directive followed by the name of that room:
*I'm on the shore of a lake
Items defined earlier in the sac file than the first %room directive are by default not in the game when it starts (though they may subsequently be brought into the game by DROP actions or similar - see below.) This can of course be changed with %at directives, since here as everywhere else, forward references to rooms that have not yet been defined are OK.
Conversely, when defining an item that should not initially be in play, it may be convenient to place the definition at a point in the sac file that places it in a room. In this case, the %nowhere directive can be used to start it off out of play. This is particularly useful if, for example, an item initially in play is later to be replaced by one that is initially absent:
damp hollow stump in the swamp
Water in bottle
# will come into play when water is drunk
(Actually, %at and %nowhere are synonyms, so it's possible to include commands like ``%at'' alone to start an item out of play, and ``%nowhere stump'' to start it in the room called stump, but this would be a bit perverse, now, wouldn't it?)
Some of the items in a game - those described above as ``objects'' rather than ``scenery'' - can be picked up and dropped. Rather than laboriously coding these actions by hand, it's possible to have the game automatically handle the GET and DROP actions. In order to do this, it needs to know the word the user will use to specify the item, and this is what the %getdrop directive provides:
Old fashioned brass lamp
If no %getdrop name is provided, then it will not be possible for the player to pick up or drop the item unless explicit actions are coded to make this possible.
The third fundamental concept of Scott Adams adventures is the actions: things which the player can do, or which can happen to him, which result in changes to the state of the world.
State consists primarily of the items' locations, but there are also some boolean flags, integer counters and saved room-numbers. The flags are all set to be false at the start of the game; flag number 15 is special, and indicates whether or not it's dark. If it is, then the player can't see without a light source.
No-one seems to know for sure how many flags were supported by the original Scott interpreters, but by inspection, Adventureland uses flags 1 to 17, missing out flag 6 for some reason, and making only a single reference to flag 4 (so that it's not really ``used'' in any meaningful sense.)
The only reference to flag 4 is that it's cleared when the axe is thrown at the bear, misses and breaks the mirror (and it's never tested anywhere). Inspection of the other axe-throwing actions suggests that this is a mistake, and that Scott intended to clear flag 3. And sure enough, the behaviour if you say at bear twice after throw axe is wrong: it understands the context-less second at bear command instead of refusing is and saying ``What?'':
Tell me what to do ? throw axe
In 2 words tell me at what...like: AT TREE
Tell me what to do ? at bear
OH NO... Bear dodges... CRASH!
Tell me what to do ? at bear
OK, I threw it.
A voice BOOOOMS out:
please leave it alone
Tell me what to do ? at bear
This is not really relevant to sac, but interesting trivia nevertheless. It's funny to find someone's bug twenty-two years after it was created!
Anyway, scottfree implements 32 flags, and a comment in the source code says that the author's never seen a game that uses a flag numbered higher than that.
There are sixteen counters available, and sixteen slots in which room numbers can be stored. The latter can be used to implement sophisticated vehicles and spells which return the player to a room that was specified earlier - for example, the YOHO spell in Sorceror of Claymorgue Castle, which moves you first to a destination, then back to where you first cast it (I think.)
Truth is, I'm not at all sure how the room-number slots are used; this facility is not used at all in Adventureland, which is the game I'm most familiar with; and looking at the reverse-engineered Claymorgue actions doesn't help much.
There are four other elements of game state: the player's current room, indications of which of the sixteen counters and room-number slots are current (since some operations act on the ``current counter'' and the ``current location slot'') and the number of turns for which the light source will continue to function. You don't need to worry about this stuff much: it's mostly taken care of behind the scenes.
%action open door
Introduces a new action which occurs when the player types a command equivalent to the one specified. Equivalent here means using the specified verb or a synonym together with the specified noun or a synonym - so depending on how the game is set up, UNLOCK PORTAL might be equivalent to OPEN DOOR.
The %action directive may optionally be followed on the same line by a verb alone instead of a verb-noun pair as above; in this case, the action occurs whenever the user provides any input beginning with that word - he may provide the verb alone or with any noun.
The lines following the %action directive, up to but not including the next directive, are conditions, all of which must be satisfied in order for the results (see below) to happen. There is no facility for specifying that conditions should be OR'red together.
Each condition consists of a single-word opcode, followed by zero or more parameters as required by the opcode. The following condition opcodes are supported:
True if the player's current room is ROOM, which must be the name of a room defined somewhere in the sac file.
True if the player is carrying ITEM, which must be the name of an item defined somewhere in the sac file.
True if ITEM is in the player's current room.
True if ITEM is either being carried by the player or in the player's current room (i.e. if either carried ITEM or here ITEM is true.)
True if ITEM is in the game (i.e. is not ``nowhere'').
True if ITEM has been moved from its original location. This includes the cases where an item initially not in play has been brought into play or vice versa, and where an item initially carried has been dropped or vice versa. This only tests the current situation, not ITEM's history - so if ITEM is moved from its original room, then put back there, this test will return false.
True if the player is carrying at least one item.
True if flag number NUM is set.
True if the current counter's value is NUM. (A different counter may be nominated as ``current'' by the select_counter action.)
True if the current counter's value is NUM or less.
True if the current counter's value is NUM or more.
The sense of the at, carried, here, accessible, exists, moved, loaded, and flag opcodes may be negated by prefixed them with an exclamation mark (!). There is no direct way to test for the negation of the three counter-related conditions.
msg It creaks open.
Introduces a sequence of results which occur if the previous %action or %occur (see below) directive is satisfied. The lines following the %result directive, up to, but not including, the next directive, are the resulting actions, which are executed in sequence.
Each result action consists of a single-word opcode, followed by zero or more parameters as required by the opcode. The following condition opcodes are supported:
Moves to the specified room and displays its description.
Redisplays the description of the current room, the obvious exits and any visible items. This is done automatically whenever the player moves (with the moveto action), gets an item from the current room, or drops an item. So far as I can tell, it need only be done explicitly when changing the value of the darkness flag.
Exactly the same as look, but implemented using a different op-code in the compiled game file.
The specified item is put in the player's inventory, unless too many items are already being carried (Cf. the superget action). This works even with items that can't be picked up and dropped otherwise.
The specified item is put in the player's inventory, even if too many items are already being carried. This can be used to give the player things he doesn't want, such as the chigger bites in Adventureland.
The specified item is put in the player's current location, irrespective of whether it was previous carried, there, elsewhere or nowhere (out of the game). This is the standard way to bring into the game items which begin nowhere.
Puts the specified item in the specified room.
Puts the first-specified item into the same location as the second.
Exchanges the two specified items, so that each occupies the location previously occupied by the other. This can be used to switch one object out of the game while bringing another in, as well as for swapping objects that are already in the game.
Removes the specified item from the game, irrespective of whether it was previously carried, in the current location, elsewhere or already out of the game (in which case it's a no-op).
Exactly the same as destroy, but implemented using a different op-code in the compiled game file.
Lists the items that the player carrying.
Prints the current score, expressed as a mark out of 100, based on how many treasures have been stored in the treasury location. This causes a division-by-zero error if there are no treasures in the game - i.e. items whose descriptions begin with an asterisk (*). So games without treasures, such as Scott Adams's Impossible Mission, should not provide an action with this result.
Implements death by printing an ``I am dead'' message, clearing the darkness flag and moving to the last defined room, which is conventionally a ``limbo'' room, as in Adventureland's ``Find right exit and live again!'' This is not a proper, permanent death: for that, you need the game_over action.
Prints ``The game is now over'', waits five seconds and exits.
Prints the noun that the user just typed.
Prints the noun that the user just typed, followed by a newline.
Emits a newline (i.e. moves to the beginning of the next line).
Clears the screen. Who could have guessed?
Waits for two seconds. Useful before clearing the screen.
Refills the lightsource object so that it is reset to give light for the initial number of turns, as specified by %lighttime.
Initiates the save-game diaglogue, allowing the player to save the state of the game to a file. Unfortunately, there is no corresponding load_game action, so the only way to use a saved game is to restart the interpreter, providing the name of the saved-game file on the command-line.
Sets flag number. In general, this is useful only so that subsequent actions and occurrences can check the value of the flag, so there are no pre-defined meanings to the flags. The only flag with a ``built-in'' meaning is number 15 (darkness).
Clears flag number.
Sets flag 15, which indicates darkness. Exactly equivalent to set_flag 15.
Clears flag 15, which indicates darkness. Exactly equivalent to clear_flag 15.
Sets flag 0. Exactly equivalent to set_flag 0.
Clears flag 0. Exactly equivalent to clear_flag 0.
Sets the value of the currently selected counter to the specified value. Negative values will not be honoured. Do not confuse this with the similarly named select_counter action!
Prints the value of the currently selected counter. Apparently some drivers can't print values greater than 99, so if you're designing your games for maximum portability, you should avoid using numbers higher than this.
Decreases the value of the currently selected counter by one. The value cannot be decreased below zero. Surprisingly, there is no corresponding increase_counter action.
Increases the value of the currently selected counter by the specified number.
Decreases the value of the currently selected counter by the specified number.
Chooses which of the sixteen counters is the current one. Subsequent decrease_counter, print_counter, etc., actions will operate on the nominated counter.
(Actually, it's not quite that simple, but it's very hard to figure out, either from the scottfree source or from the reverse-compiled Sorcerer of Claymorgue Castle, precisely what this does.)
Swaps the player between the current location and a backup location. The backup location is initially undefined, so the first use of this should be immediately followed by a moveto to a known room; the next use will bring the player back where it was first used.
Like swap_loc_default but works with one of a sixteen numbered backup locations, nominated by number. Swaps the current location with backup location number, so that subsequently doing swap_loc again with the same argument will result in returning to the original place. This can be used to implement vehicles.
Performs a "special action" that is dependent on the driver. For scottfree, this does nothing.
Never use this action. It is used internally to allow a sequence of actions that is too long to fit into a single action slot, but there is no reason at all why you would ever explicitly use it: in fact, this kind of low-level detail is precisely what the Scott Adams compiler is supposed to protect you from. I don't know why I'm even mentioning it.
%comment need key in order to open door
This directive allows a comment to be associated with an action in the Scott Adams format data file written by sac. The comment is attached to the most recently declared action. Note that this is very different from the usual kind of comment introduced by the hash character (#) which is simply discarded by the compiler.
Why would you ever want to use %comment? Beats me.
Like %action, the %occur directive introduces a sequence of zero or more conditions which, if fulfilled, will allow some consequences to result. The difference is that %occur actions occur irrespective of what command the player supplies - indeed, they happen before anything is typed. They can be used to implement circumstances such as falling off a ledge if in an appropriately dangerous room while carrying a particularly heavy item.
If an optional argument is supplied then that argument is the percentage chance of the occurrence happening when its conditions are all satisfied; otherwise the chance is 100%.
There is one more very important difference between actions and occurrences: before each turn, every occurrence whose conditions are all satisfied is executed. Then at most one action will happen: the first action matching the players command and whose conditions are all satisfied.
Finally, we come to the global parameters, a rag-bag of bits and pieces which affect the game as a whole. In general, each of the following directives should appear exactly once: it's an error for any one of them not to appear at all, and a warning is generated if any is used more than once.
This simply specifies a number which uniquely identifies the adventure. I have read in the Definition file that comes with the scottfree distribution that this number (and all others in the Scott Adams file format) is ``apparently 16 bit''. I don't know how this is apparent, but it's possible that some interpreters will choke on numbers larger than 65536 (2^16-1), or maybe even 32767 (2^15-1) if they interpret the value as signed. So you should probably pick a number smaller than this.
Somewhere out there, there should be a register of all Scott Adams format games, each with a unique identifier number. Unfortunately, I don't know if there is one or where it is - please contact me if you can point me at it (or if you want to start maintaining one!)
Also unfortunately, the uniqueness of the register is already well and truly broken (although that doesn't mean we should break it more, of course!)
Adams' original series of twelve adventures uses numbers 1-12 (Adventureland has the coveted number 1, of course!), and the later Sorceror of Claymorgue Castle is number thirteen. Unfortunately, Return to Pirate's Island and The Adventures of Buckaroo_Banzai are both given number fourteen; and the two Questprobe adventures, The Incredible Hulk and Spiderman are both number two again (the same as the original Pirate Adventure. What a crock. At least the Adventureland ``sampler'' that used to be given away for free has its own number, 65.
To make matters worse, Brian Haworth's series of eleven Mysterious Adventures re-use the numbers 1-11. So there are no fewer than four adventure number two's. Ho hum.
Specifies the version of this adventure. Looks like Adams went through 416 design iterations before he got Adventureland into a state he was happy to release.
Specifies the number of significant letters in each word known to the game. Because this is three for Adventureland, all longer words can be abbreviated to three letters - so the player can type CLI TRE (or indeed CLIMAX TREMENDOUSLY) instead of CLIMB TREE.
Specifies the maximum number of items that the player can carry at once - if he tries to pick up something else, the interpreter issues a suitable message.
Specifies how many turns the light source is good for. Light is only used up when the light source is in the game, so, for example if there's an unlit lamp in the game and a lit lamp initially not in the game, the light time doesn't start to tick down until the lamp is lit (i.e. the lit lamp object is brought into the game.)
Specifies which room the player starts in.
Specifies the room in which the player must store treasure for it to count towards his score. Remember that treasures are, by definition, objects whose name begins with an asterisk (*). The player's score at any time is defined as the number of treasures that have been stored in the treasury, divided by the total number of treasures, multiplied by 100, and rounded to the nearest integer (so that it's always in the range 0-100.)
The special room-name - may be used to indicate that treasures must be carried in order to contribute to the score, rather than deposited in a particular place.
Nominates a particular item as the light-source for the game. When flag 15 (darkness) is set, the player can only see if either carrying or in the presence of the lightsource object. There can be only one lightsource in the game - if a second is nominated, it replaces the first.
%nalias lamp lantern
%nalias lamp torch
Creates an alias for a noun. Multiple uses that share one of the same words (as in the example above) create an equivalence class of words that are all mutually synonymous.
%valias take get
%valias drop leave
Creates an alias for a verb.
Includes the contents of the specified file, exactly as though they were included inline in the SAC file being processed. Non-absolute paths are interpreted relative to the file being parsed at that time, not relative to the working directory. For, for example, if the file subdir/thrick.sac is being parsed, and has a line %include frog.sac, then the file of that name in the subdir directory is used.
The tutorial, Games::ScottAdams::Tutorial.
Mike Taylor <email@example.com>
First version Wednesday 11th April 2001.
To install Games::ScottAdams, copy and paste the appropriate command in to your terminal.
perl -MCPAN -e shell
For more information on module installation, please visit the detailed CPAN module installation guide.