The Narrative and Crossword Get Friendly
 -- on The Use and Deployment of Puzzles
<pre>
Contents
Introduction
 A Thought
 The Role of Puzzles
Thinking Like A Player
 Hunter-Gathering
 Research
 Simulation
 Intuition
Thinking Like an Author
 Plot
 Geography
 Hooks
 Sheer Amusement
 Rewards
Conclusion
 Finally
</pre>
-----------------------------------------
<P>
<P>
I - Introduction<br>
=================
<P>
Since I started writing Interactive Fiction four years ago I've spent a fair
amount of time not just creating but trying to introduce and explain it to other
people. The synopsis given always begins the same way: "You remember those
gamebooks where you choose which paragraph to read?"
<P>
 To most IF devotees (including myself) such a description is toe-curling, and
massively inaccurate. "IF," we exclaim, "is nothing like a gamebook. They were
toys - and this," (here our eyes flash with artistic madness), "THIS is real."
That said, a mathematician (such as myself) might say IF is just a gamebook with
a wider parameter space - instead of five options per paragraph there might be
three hundred. Oh, and with the options not on display. So where does the border
line between the toy and the experience occur?
<P>
A Thought<br>
----------
<P>
 I would argue that IF is made what it is by the prompt - the blank chevron
that waits, blinking and mocking, for the player to have an idea. You can
interact with it without thinking, of course: you can type "LOOK" or "INVENTORY",
and indeed do so repeatedly. But to make any progress in the game-world, and in
its story, the player is required at some point to think of something to do;
something which is then further constrained by the set-up of the game-world and
the vocabulary of the parser. It is in this process - in which a player is forced
to think in the context of the world and translate his ideas into a form that can
be understood - that the sense of immersion, "mimesis", the plain old suspension
of disbelief that IF junkies live for, is generated. The important element of
Interactive Fiction is not the ability to decide, it's the requirement to
consider that decision first. She must therefore read the text, closely; picture
the world it describes, perhaps imagine the character she is playing and so move
herself into the story, losing a little of the chair beneath her  and the screen
in front. What this idea boils down to is simple - if a game's parser could
execute "WIN GAME" then something of the magic would be lost.
<P>
The Role of Puzzles<br>
--------------------
<P>
 So how do we, the writers and designers of an IF game, encourage the players
to make this effort? (And it is an effort - so many people introduced to IF get
bored after the first few moves; indeed, so many regular players still do. IF is
perhaps one of the hardest mediums with which to get involved emotionally, simply
because it requires more than just an exercise of the eyes or ears). 
<P>
 The
answer is two-fold: carrot and stick. Graham Nelson wrote in his seminal essay
"The Craft of Adventure" (1995): "The author of a text adventure has to be
schizophrenic in a way that the author of a novel does not." That is, when
designing an text game it pays both to think both as a writer and a player. In
thinking as a writer, you need to ensure they cannot help but engage - that they
need to think at the prompt, that they need to be aware and awake when they are
asked ">"? by the game. If a lazy player can complete your game simply typing
"WAIT" (or more probably, just "Z") at every prompt, then what's to ensure they
read any of the text at all?
<P>
 In thinking as a player, you need to make the game accessible, and rewarding.
You have to ensure that the thought the player is putting in is worthwhile.
Perhaps more importantly, you have to ensure they believe the thought to be
worthwhile. If you are a writer with a famous name, then this should be easy. If
not - you may need to bring every skill to bear to prevent players quitting in
the first three turns of the game.  In this approach - that of enticing
players with the promise of reward for the payment of thought - the puzzle is
perhaps the strongest tool you can apply. This two-edged beast glares stoically
at the player through the glass, telling her that if she is capable, and if her
thought is up to its, then she will proceed and be rewarded. A pause for
consideration, maybe, or a series of frustrated attacks before a problem is
defeated is then rewarded both in the game - as progress, or perhaps sheer mental
satisfaction - but also more subtly, by having had the player think herself into
the world.
<P>
 Here we ought to define puzzle. A Tower of Hanoi is a puzzle, so is a maze.
So is a code, or a complicated system of pulleys. However, puzzles are not
restricted to little trinket-boxes that one might get in a Christmas cracker
bought from the Science Museum catalogue - they extend to anything for which the
correct method of procedure is not immediately visible. Interaction with another
game character might classify, from the standard (feeding the animal with food,
so that it doesn't notice you leaving) to the more cunning (upsetting the
grandmother with a photograph of her late husband, so that she doesn't notice you
leaving). A closed, unlocked, well-hinged door, in a game which understands the
verb OPEN, is not a puzzle. The same door, if found in Carl Muckenhoupt's "The
Gostak" (2001), is a puzzle - because that game is entirely in an invented
language, and finding what the word for OPEN (and indeed, deducing the presence
of a door) is extremely difficult indeed.
<P>
 This leaves "puzzle" as an unhelpfully wide category. We now proceed to look
more closely.
<P>
<P>
II - Thinking Like A Player<br>
============================
<P>
 Magicians have long known that the way to cover a trick is with a careful
patter, distracting and involving the audience on the one hand whilst the other
is frantically rooting around in a pocket for the right playing card. Similarly,
they've known that the easiest way to invent a new trick isn't to invent a new
mathematical device, or a new black-velvet-box-with-string, but simply to dress
up the same trick in different patter. An audience with no knowledge of magic may
well never realise that five cards tricks are all the same, and indeed, that they
are the same as the appearance of a lit cigarette behind the magician's ear or of
a new Fiat Punto in his garage.
<P>
 And conversely: someone who does know how the trick works (say, the magician
himself) will categorise all these seemingly-different variants by the underlying
mechanism behind them, rather than as "card tricks" or "cigarette tricks". In
viewing the player's approach to the puzzles, we need the same idea: rather than
thinking of "puzzles involving mazes", "puzzles involving keys" and "puzzles
involving the Archbishop of Canterbury"; the important issue is the mechanism by
which the puzzle works. Here the metaphor with magic breaks - whereas the
mechanism of a card-trick might be a sleight of hand or mathematical device, in a
text game the mechanism by which the puzzle works is the mechanism by which the
player works the puzzle. That is, the way the player (ideally, not counting for
luck) is supposed to solve the problem. So; the problem of finding a gold key for
a gold door is the same puzzle as finding cheese for a hungry mouse - both rely
on an obvious connection, and the finding of an object the player will guess is
present even before he sees it. On the other hand, finding a full-length mirror
behind which to hide when slipping past a vampire, is a very different puzzle
indeed.
<P>
Hunter-Gathering<br>
-----------------
<P>
 Every puzzle game for time in memorial has had a fork under a table, a diary
under a bed or a handkerchief in a handbag. Generally speaking, authors of games
don't like to leave every important object in plain view, just lying around; they
prefer instead to stack them tidily away. Before this was easily possible (in the
early Cambridge games published by Acornsoft and Topologika, for instance) they
would still trouble to hide things in convoluted maps (the woods at the start of
"Colossal Cave") or full-blown mazes ("Crobe", "Fyleet", "Zork", etc). Is this
squirrel-like instinct of designers a true puzzle?
<P>
 The answer is sometimes, and usually only then in retrospect. When a player
ransacks a house top to bottom it's usually done with the aim of ruthless
efficiency rather than cunning. Many old-school players (my brother is one of
these) will enter rooms, examine all available nouns, then look under, open,
break and kiss everything; only then leaning back to steeple their fingers and
think. [FOOTNOTE: Players such as these are completely lost when dropped into a
deeply implemented game. I have yet to convince my brother to play J. D. Berry's
excellent Art Show winner "Ribbons"; but I imagine he'll be there for a full hour
before moving onto the second room. I hate to think how long it would be before
he realises there is only one after all].
<P>
 This is a perfectly valid method of solution for what is a perfectly valid
design choice. Some exponents claim that "LOOK UNDER" is now outdated, but in
fact it serves a clear function. A player, if trapped into a small enough set of
locations, will read every description twice and take his inventory every turn.
By hiding things (say, the key to leave the first room of the game), you force
the player to familiarise himself with what is available (say, his identity and
his initial inventory items). You can be reasonably sure that a player who has
hunted every nook and cranny for his sister's diary will have found the hairpin
with which to pick the lock, and indeed, may even have put on the reading glasses
he's carrying before the tome is open. Further, if later on he finds an ice-cube
containing something he needs (a particle of guilty conscience, perhaps, in the
style of Meretzky and Adam's "Hitch-hiker's Guide to the Galaxy"), then you can
reliably expect him to think very quickly of the blow-drier on the dresser, just
by the bottles of spot-
cream.
<P>
 And just as one room, or one collection of objects can be made familiar, so
can the game map itself; if you force the poor player to traipse backwards and
forwards for a while, so that in later scenes of the game it will be quite
alright to require him to trace a route with step-perfect accuracy. If your game
is going to have a car chase later on, it seems only fair to allow him to learn
the street map. Since your player may not realise this will be important, it
seems only fair to force him to do so, too. On an immersion level, a good use of
searching rewards the player with a wider vista, a deeper visual model and the
certainty of where to find a telephone.  A really good use will do so without
the player noticing.
 <p>
 The problem is, players are wise to this sort of thing, and quickly resent
any attempt to make them type repetitive things. Hiding an important object
amongst several identical containers (say, a tree in a forest) is unlikely to win
respect, just as hiding an important room in a tangled maze with no map or clue
as to the goal is widely considered a fatal mistake. Indeed, if you start a game
with a large map or inventory, many players will turn off on seeing the first
choice of direction. Nelson's seminal 1994 game "Curses" audaciously opens with
around twelve rooms and expects us to draw a map; by contrast all of Plotkin's
games, with the possible exception of "A Change in the Weather" (1995), begin
with the player chained to the spot, or at least moving in a straight line (not
that "Weather" is a loose and unshackled game).
<P>
 To get around this, you either want the player not to notice what you're
doing, or to be convinced that it will be worth it. The first can be achieved by
including one large, complex, possible insoluble-at-the-
time puzzle in plain view, in the middle of a room which needs to be ransacked.
The player, in between staring and restaring at the chess problem before him,
will hopefully find the pawn under the rug. In "Curses", the author can be sure
that, eventually, a frustrated and bumbling player will find the four-leaf-
clover which is waiting for him, almost from the very beginning of the game.
<P>
 The other method is aided by a strict (and possibly "metaphysical") control
of how much ransacking the player must do. Plotkin's "Shade" (2000) opens with a
search for plane tickets, which will always be in the last place of three you
look - enough to achieve its effect (a bit of irritation, a bit of
familiarisation, and a lot of contextualisation ready to be attacked in the
game's later phases) - but not enough to outstay its welcome. Similarly, an
old-school player of "My Angel" (Ingold, 2000) will find the knife in the
hay-barn long before more careless players tread on it underwater, several
locations further on.
<P>
 A nice touch to reward the player and elicit some forgiveness for having them
running around like children, is to give your treasure hunt an elegant solution.
The jigsaw-piece in the pyramid in "Jigsaw" (Nelson, 1995) will be found by most,
but found quickly by those who have ever done a real jigsaw. A player - or one
who notices, anyway - will be pleased to find the diary under the pillow, the
watch in the magpie's nest, or the new car in the avaricious magician's garage.
Even if she only found an object by typing every permutation of verb and noun she
could summon up, it will at least feel more worthwhile if there was a good reason
for it to be there.
<P>
Research<br>
---------
<P>
 Just as most puzzle games have a hidden key, most will also have a
combination lock. Here the "object to be found" is non-physical and stored in the
player's head rather than his hands. The canonical example of a research puzzle
is a magic potion; where the right books and cross-references yield a list of
random objects which can be boiled up to create infinite youth ("Christminster",
Rees, 1995), deep sleep ("The Mulldoon Legacy", Ingold, 1999) or violent
explosions ("Trinity", Moriarty, 1986). This is a much cleaner and more efficient
(and perhaps, more prone to bit-error) type of hunting puzzle; but works in
essentially the same way.
<P>
 However, there is room for much more, as research offers a perfect
opportunity for the author to sit the player on his knee and tell him a story,
and furthermore, to force him to listen - or more importantly, force him to ask.
A locked door will act as an infallible ice-breaker with the Palace Guard (who
may prove to be a fascinating, deep and humorous fellow). The need for a password
to begin that conversation will have the player happily reading every volume in
the British Library (so long as you've convince him the puzzle is still fair).
Along the way he may need to understand the crazy indexing system - but no doubt
there's a book that will tell him how. And if that book drops information on the
weird old man who built the library, his alchemical secrets and the tragic fate
of his sister, then so much the better. Indeed, it could be argued that this kind
of retrospective, detective-like story-telling is what Interactive Fiction does
best. "Curses" constructs its story entirely by in footnotes, in the form of
biographies and diary entries. A measure of the skill here is that, of course,
the "Vol. II" label on the book "History of the Meldrews" cannot help but raise a
smile in anyone who has played the game. Similarly, games often have players
exploring places long abandoned or emptied; partly because it means less
characters to code, partly because the player can then fill in the plot from
researched snippets.
<P>
 Actual research-based puzzles tend to fall into three sub-categories:
Bookword, Librarian and Genus. A Bookworm problem is the direct equivalent of a
smash-every-cabinet hunt: the player is given eight books and not allowed out
until he knows Chinese. This can obviously be pretty unfair - and pretty tedious
- and is probably best avoided unless the contents of the eight books are very
interesting, or very funny, as of themselves. A much better way of posing the
same problem is the Librarian approach, which is the same, except that the game
doesn't put the books on the table but has them neatly on the shelf, with the
player left to find them. The crux of the difference is the additional thought
involved - it's no longer just enough to read a book, you have to think of which
book to read first. The player must choose a title, or a chapter number, or a
topic on which to interrogate a character; and in finding the right topics to
approach she will immerse herself just that little bit more, paying more
attention to what is said. Essentially, you may have a better chance of making
the player care about the rambling old man's comments on the safe if she has
realised, of her own accord, that they may contain a clue as to the combination.
It's about striking a balance between the game telling the player what is
available for her to find, and the player feeling as though they have discovered
something on their own.
<P>
 Finally, Genius (or more properly, Genius!), is reserved for those research
puzzles which take the Librarian model to its intuitive climax, by requiring the
player to work out, through a leap of logic, what topic to research in the first
place. All the best examples of this are in "Curses": the romance novel problem
or the prayer book, for example (though finding the English Bible in
"Christminster" also qualifies). These are puzzles where that elusive starting
point of information is clued subtly and cunningly, and in solving it the player
will feel a great rush of satisfaction. A good research puzzle can be hugely
rewarding, both in terms of plot-progression and immersion, and sheer
crossword-puzzle entertainment; with the bonus of allowing you to wheedle your
fiction even further into a player's mind. Although the "CONSULT" verb appears to
be going out of fashion somewhat, in favour of the more direct but more difficult
to code "ASK ABOUT"; the effect is still much the same.
<P>
Simulation<br>
-----------
<P>
 Simulation is an inherent feature of the IF medium; any game is a narrative
at war with a crossword inside a VR boxing ring. To some extent it could be
argued that any and all manipulations of objects are simulated (indeed, that this
is true by construction) - but by this argument, gamebooks are also simulated in
a specific case-by-case way: so this section will reserve the term for those
interactions which the game can process in a generic fashion. From the player's
point of view, this therefore covers those interactions where some general rule
that the player learns in one set of circumstances (say, a light source allows
you to see) is still applicable in a different but comparable set. To give a
concrete example, a microwave is not simulated if the only thing that can be
heated is a microwave meal (anything else meeting with a "Why would you do that?"
message, say); and is simulated if a player can heat more or less anything - cups
of water, maybe, or plastic rods. A decent simulation should also allow the
player to blow himself up (or at least, be warned specifically not to) by filling
it with metal trinkets.
<P>
 The standard IF simulations are quite familiar: takeable objects and the
player's inventory, systems of containers and supporting objects which can nest
(an arrow in an apple on a terrified boy's head), and also the opening, closing
and locking of doors. Geographical simulation loosely covers the compass
directions and vertical motion, though what goes up will not come down and north
need not be inverse to south. Within locations there is little geography - the
concept of "next to" is extremely rare (the boy is not by the tree, even if the
arrowhead is contained in the bark). Later versions of languages may well extend
these - Mike Robert's TADS will handle sound-passing in its third release - and
many code-
snippets of Inform exists handling moveable people, pourable liquids, even
writeable notepads.
<P>
 The current default behaviour (doors, for instance) has the advantage of
being common knowledge, taken for granted by experienced players and picked up
quickly by the novices. (Though perhaps a few are frustrated that "PUT KEY IN
KEYHOLE" is rarely a way to unlock doors). However, most games at some point
extend the simulation in some way - with magic spells or microwaves, robots or
wrist-watches. By doing so, a whole new avenue of puzzle development becomes
available.
<P>
 These usually take the form of strategy puzzles - in which the result and
process are clear, but the ordering of steps becomes important. The most simple
simulated problem is the Tower of Hanoi (the irritating children's toy involving
stacked discs on pegs) - where the goal is stated (move stack from peg A to peg
B), the governing mechanics are clear (one disc moved at a time, larger discs
always below smaller); but the problem is to apply the correct move at each
stage. Chess problems are a similar idea, though much more complex in nature. IF
takes this concept and codifies it into the manipulations of containment,
visibility, gravity and so forth. Most also make use of timers - the simulation
of events occurring outside of a players control. "A Change in the Weather"
simulates a thunder-storm into an extremely evil timing puzzle. "Metamorphoses"
(Short, 2000) simulates a variety of substances and the ability to morph objects
between them, and then has puzzles which require fragility, or density, or
flammability in the object produced. Although this game does not, it could be
easily extended to a full strategic challenge, in which a player must balance his
hoop-shaped resources against the need for glass objects, and so forth, and not
burn everything in one go, say. Cadre's "Varicella" (1999) takes this idea to an
extreme, in a game in which the simulated actions of several people in a palace
are tightly interwoven, with the player attempting to thread a manipulation of
his own through the mesh. This codifying process, however (unlike the abstracted
business of research problems) has a very real effect on a player's sense of
immersion into the game, arising from the fact that - unlike reading about topics
in textbooks - her very actions are now subject to new rules and forces which the
player may not be aware of.
<P>
 The player entering an IF game will start with some hazy expectations of what
is simulated and what is not. She will expect, for example, to be able to carry
small things around with her, though she may not be sure whether she can carry an
unlimited number, or an unlimited weight. She will most likely not expect to be
told which hand she's carrying things in, or which pocket, and will probably
become annoyed if told her hands are too full to push door handles if she's
carrying two items (even if this may be true in real life). To say the simulation
should be as accurate as possible is quite simply untrue; player's automatically
expect a level of simplification on entering the text game world. No novice will
expect to have to type "BLINK" every four moves. However, they may be (and, I
find, often are) surprised to find "WALK OVER TO DESK" is not understood. The
same trend persists in experienced players - the best example being in
conversation with game characters: players will not bat an eyelid (i.e. blink) if
asking the same question elicits a word-for-word repeat of the response, for the
simple reason that this is what games have done time immemorial. Further, most
players will not complain when a poison gas puzzle cannot be solved by typing
"HOLD MY BREATH" (there being no "breath" object in the game-world), but
conversely if this is the only solution players are likely to be irate and demand
to know how they were supposed to think of something so outlandish. 
<P>
 What we
have here is the Interactive Fiction version of Chekov's gun; the old principle
that if a gun is to be fired in Act III, make sure it is visible on the
mantle-piece in Act I. If a puzzle relies on the player knowing that waving a gun
around will make characters react, then you'd better show him early on that
characters can see what he's waving. Further, they'd better react to everything
else as well - no good them seeing a bloodied murder weapon if they don't see
their wife who's been killed by it.
<P>
 The two important things then are consistency, and re-education. Consistency
consolidates the player's world-model; if it breaks in a few places most players
will believe they've encountered a bug, if it breaks in almost every place then
most player's won't believe it's simulated at all, and will not expect it work
elsewhere. If you want the player to know how your game-world operates (what
liquids can do, what fire can do, so forth) then you must be prepared to make
sure it does everything one would expect. This doesn't mean every fire has to
potentially devour the entire game-map; but it does mean every sheet of paper
stuck into it won't be described as "Unlikely to do anything". "Everything one
would expect" means "Everything one would expect on the basis of what has already
occurred," not "on the basis of the real world." The real world is neither here
nor there.
<P>
 Re-education is the subtler point, and one not commonly implemented, except
in platform games. The popular "Tomb Raider" series of games, published by Eidos,
introduces the various jumps, rolls and runs the heroine can perform in a series
of simple, obvious challenges on a "exercise course" level. This serves to allow
the player to practise, not just the act of performing a manoeuvre (which is not
relevant in a text-game, unless it is a typing tutor), but also the process of
gauging distances and timings. Similarly, an IF game which extends the simulation
should give the player a series of simple manipulations to perform so that they
learn how the simulation works in various conditions; how liquids respond to
heat, whether some objects float, if flame spreads to nearby objects. If the
player must produce a noisy distraction in the endgame, then make sure, earlier
on, he inadvertently knocked over a vase and brought the housemaid running. If a
character will reveal more information on repeated interrogation (maybe if the
player now knows more about the topic himself and so "phrases the question
differently"), then make sure the player is forced to ask the same question
repeatedly at some point, even if you employ a simple, pointed "Perhaps he's not
letting on all that he knows." at the end of his first surly reply.
<P>
 A well-designed set of simulation puzzles start with those which shift the
player's expectations of what the game will understand, then consolidate it, and
then rely on it for more and more complex puzzles exploiting the ways the various
features interact. [FOONOTE: Which is to say, "Lemmings" is one of the
best-designed games of all time.] The characters in "Christminster" work on this
principle, with the player finding more and different ways throughout to cajole
Edward into helping her, and to use his various skills (or lack of) to further
the game.  Another branch of simulation arises in sufficiency puzzles, where
the player looks around the current map, or object list, with the knowledge that
he must be able to do something, and proceeds to deduce what it is he needs to
do. This is a solution-method which requires the player to look at the simulation
in its most abstract form: a set of objects available, a limited set of rules,
and the knowledge there is a correct route. Effectively, he is viewing the
situation as a brief puzzle-tree set within the narrative. An excellent example
of this is the award-winning puzzle from "Spider and Web" (Plotkin, 1998)
concerned with escaping from the chair. The player will not solve this by thought
through cause-and-effect, simply because he does not have enough information -
but rather by looking at the only options available to him, and the knowledge
that one must be right. It should be noted that requiring a solution by this
method has a negative impact on immersion - a player looking at the design of the
game, and at available information, is not a player emoting. In game such as
"Spider and Web", which places a distance between player and player character,
this isn't too much of a problem. Similarly, in wider puzzle-oriented games it
will not matter either. Games in-between should be careful, though, as otherwise
they give their protagonists something verging on precognition.
<P>
 If the simulated aspect of a game is well-executed it will both extend the
design possibilities in unique ways and allow for interesting new puzzles (the
Enchanter trilogy of Infocom introduced magic spells to great effect) but it will
also increase the player's confidence in the author, allowing for more and more
ambitious leaps of logic to be expected as the game continues. If the game
remains fair, then players will expect it to remain so and be willing to give you
the benefit of the doubt on later, harder, problems. This leads finally to a
branch of problems which can only be described as "beta-tester puzzles"; being
those which the player solves less from a desire to overcome an obstacle and more
from a desire to break the game and come out with a permutation which has not
been accounted for. A good example is the robot cleaning mouse in "Starcross"
(Lebling, published by Infocom 1982) which disappears into a service hatch at
various intervals, leaving the curious player to wonder if the room beyond is
actually implemented or not, and devise a nefarious method of entry. These
puzzles can be some of the most satisfying to solve, as the player will feel
quite certain before trying his solution that it should work, but they can also
be some of the hardest, because there is no direct indication in the game that
there is a challenge to be attempted at all.
 <p>
Intuition<br>
----------
<P>
 These are an examples of intuitive puzzles. The definition of an intuitive
puzzle is essentially "an unfair one"; as these are the problems in which the
player is expected to make a mental leap on the basis of little logic and very
few, usually obscure clues. They are the black magic of puzzle design;
game-quitting failures when they miss and immersion-creating moments of true
connection when they work. There are a hundred examples, and whether they work or
not often depends on the individual player, and how receptive she is to the
subtler hints of the authors general mode of thinking. A few have been touched
upon already - the Genius! category of research; the beta-tester mode of
solution; these both rely on leaps within the player's mind.
<P>
 A concrete example of a puzzle uniquely in this category: the chipped square
in Plotkin's "So Far" (1996). Here the player is given an alien object in its
natural setting with a few clues to its function which are only really
comprehensible in retrospect, and asked to deduce its operation. It's a pretty
simply object, and a one-word solution, but the important point is that, once
solved, it all seems clear and natural. The square's minimal decorations and its
notch are transmuted from opacity to transparency in a flash. These are the
puzzles the player can solve at the bus-stop; he can wake up and know that the
idea he has had is right. (It was while waiting for a 42W that I worked out what
the soft grey brick in "Zork II" (Lebling and Blank, 1982) was for, after a three
year break from the game).
<P>
 Hints are crucial to intuitive puzzles; the best are those a player only
realises are hints once the puzzle is solved and yet somehow plant the seed of
solution in the player's mind. They can be placed in a thousand ways - and
perhaps should be in as many as possible - though elegance is an obvious plus.
"So Far" is excellent in its hinting, simply by constructing a logic behind every
puzzle but refusing to present anything but the elements at face-value, leaving
the player to construct every implication.  This is the same mechanism by
which cryptic crosswords work; that the player knows, for certain, when she's hit
on the solution - though there are several 8 letter words for "most likely to
lose", there is only one which is an anagram of "grounded". Now, cryptic
crosswords are solved mainly by working out the way the setter writes clues, and
learning all his idiosyncrasies. A simpler approach works in text games - the
puzzles in "So Far" share a thematic feel (beyond simply being really rather
hard) - so do the puzzles in the author's earlier "A Change in the Weather". Fans
of Infocom's David Lebling admire his tight logic and scientific use of
cause-and-effect in games like "Starcross", "Spellbreaker" (1985) and "Zork III"
(1982); and there is a clear contrast with Brian Moriarty's more sprawling works
"Trinity" and "Wishbringer" (1985). (If nothing else, Lebling would never have
written a game designed to be easy).
<P>
 The leaps of intuition made by a successful player have a heavy payoff, as
suddenly instead of the player having to read the mind of the author it seems the
author has read the mind of the player. (This is of course not the case, in fact
the former has occurred, but it's a lovely effect to generate). By tuning oneself
into the author's mindset the player becomes more deeply immersed in the patterns
of game-world and story, and by allowing himself to believe in [the existence of]
an underlying logic, the world develops a continuity outside of the players
interactions and feels all the more real. These are the puzzles which remove the
game as far from a game-book as is possible - when the action to be taken must be
constructed almost in its entirety in the player's mind before it can be applied
to the game itself.  Often, the best intuitive puzzles are easy ones - where a
player walks into an area an immediately types the correct input, without really
knowing how. Many players found the puzzle with the hatchway in "Spider and Web"
to work this way; myself I spent about half an hour with permutations of boxes
and wrenches, far overcomplicating the problem. Similarly, I think the best
intuitive puzzle I have ever written myself is at the start of "All Roads"
(2001), in which the player's hands are tied with rope and the only available
object is a bottle of wine. Yes, the solution is quite clear - but to produce it
the player must take the phrase "bottle of wine" and apply his knowledge of what
bottles of wine are really like. To do this she must fully visualise the object,
and this situation is elevated from being an inventory listing:
<P>
 You are carrying:<br>
  a bottle of wine
<P>
...to a character, holding a bottle between loose and shaking fingers.
<P>
 Many good intuitive puzzles work by this method - expecting the player to
take his knowledge of the real world and assume that the game follows the same
rules.  However, it should be stressed - use intuition with caution. If used
too much players may feel utterly adrift, without any help at all. There is a
fine line, and an art, to producing puzzles which can be fairly solved by no
systematic means at all.
<P>
<P>
III - Thinking Like an Author<br>
==============================
<P>
 Just as there is an art to designing puzzles which will linger in a player's
mind, there is also an art to codifying them into ropes and rabbits and
rodeo-machines and placing them in the right order to achieve your effect. This
is where the authorial mindset comes in - in planning the structure and plotting
the order by which you unfold your story and your world. Here the games status as
narrative and crossword becomes quite pointed, as puzzles can be deployed to aid
either or both. The following sections detail the most important areas of
influence.
<P>
Plot<br>
-----
<P>
 The most obvious use of puzzles is to slow down plot development, and allow
interaction to break up the text from a single chunk into a series of responses.
In an old AGT game, "Murder at the Folkestone Inn" (Anne Laughlin, 1993), the
plot occurs entirely in room descriptions, and the player simply moves from one
to the next to experience the story. Most games are more sophisticated than this,
but the basic idea is perhaps the same. Puzzles can be used as a device to
bullet-point the plot and also have the story react to the player's presence in
some way (fixed or flexible, it doesn't matter).
<P>
 Gareth Rees remarked in an article on the design of "Christminster" that the
motive for one puzzle - in which the player is trapped in a small room with
Professor Wilderspin - is to force the player to talk to him, even though this is
not important to the solution of the problem. This is an example of another trick
- using a puzzle to constrain the player's ability to wander away from something
they should be paying attention to. This can be just an extension of the Research
puzzle idea; just as you can bury a password in a family history book, you can
bury a key in a family graveyard, and either way the player must scavenge through
the past if he wants to continue, collecting information along the way. It can
also be more active, having the player confined to an area in which events are
occurring; or indeed, having the player's solution to a problem affect the plot
in some way. (Taking care to ensure the outcome does not feel too arbitrary,
otherwise the player may start taking his decisions without any thought, just as
he does in a gamebook.) There will come a point in the game, of course, when the
plot is interesting enough for it's own sake that players will be happily rooted
to the spot - however, if they are not, providing them with a point of interest,
a point on interaction on which to centre, is a clear way of drawing attention to
anything important around. In a way, this is the Hunting idea again, only now the
search the player does not realise he is on is for the story-line itself.
<P>
 Interactive Fiction needs this sort of device to pace it, due to the inherent
lack of structure arising from the flexible pace of the player's progress. More
cunning ways are available, not using puzzles - a game could keep track of how
well a player was doing and advance the plot if he is failing to do so, for
instance. However; puzzles are probably the easiest - and most widely understood
- mechanism to date.
<P>
Finally, puzzles can form the very stuff of your story - making them attractive
to the plot-hungry player and decisive in your game design. The chair problem of
"Spider and Web" is a classic example of this, being a moment where the plot
moves round and become something quite unexpected. Placing this on the end of a
puzzle allows the player to feel that it's her achievement, that it's her work
which has produced the outcome - and allows make the player properly receptive
for the moment, when it comes. She will be reading more closely after solving a
problem than whilst simply exploring around.
<P>
Geography<br>
----------
<P>
 A player mapping a game uses the same convention that authors do; no open
hallways or expanses of grass and trees sketched in delicate pastel shades, but
rather boxes on a grid with lines for doors, and the occasional frown of
irritation when presented with an up/down connection. Each location is marked out
as a separate object are linked by teleportation walls which could be vertical,
horizontal, widdershins or inside-out for all a player may care. There are ways
to try to alleviate this - designing maps that fit neatly together, or
implementing larger rooms in two or more sections to give the sensation of space.
But the real problem is the lack of connectivity between discrete locations, and
is this best overcome by implementing something which causes the rooms to bond. A
game may include, for instance, a roaming character who goes from room to room,
(such as the thief from "Zork") but this sort of approach is not tailored towards
the player's own actions and so feels less relevant. (Indeed, the thief never
made "Zork" feel like a real world - being more just a source of irritation for
mappers, treasurer-seekers and anyone trying to avoid the grue).
<P>
 The solution once again comes down to thought - to placing the idea of
connectivity into your player's mind. If he is told - by the entrance of a thief,
or the presence of a river - that rooms are connected, he will draw a line on his
box-grid map as required. If, however, he is required to realise that the
solution of some puzzle relies on a continuity between locations (floating
something down the river, or setting a trail of gold coins for the thief), then
the act of thinking of this connection will implant it firmly into the player's
mind. It's the same idea again - that forcing a player to visualise rather than
catalogue the text game world will increase his immersion within it. So - by the
construction of puzzles which exploit geographical links - chutes from floor to
ceiling, windows looking out over other rooms, pulleys down well-shafts or
attached to mine-buckets - we glue the map together. Indeed, Nelson wrote in "The
Craft of Adventure" that a good game map has a river running through it, and this
is true - but note your river could equally well be a conveyor belt, a
dumb-waiter, or anything else which allows remote manipulation of one location
from another.
<P>
 This also allows for pleasingly devious puzzles. One could have a search for
a secret door motivated by a 'hole' in the game map, which then requires the
player to deduce which room is above the missing space and work his way down. A
time-travel game could allow the players knowledge of the future map to influence
his explorations in the past. A game based on C. S. Lewis' "The Silver Chair"
could have players exploring a region which, when viewed from above, spells out a
message. And so forth.
<P>
Hooks<br>
------
<P>
 "Lemmings" is one of the best designed games ever, and is also one of the
most addictive. Why? Because the basic problem is so easily remembered, and so
frustrating tricky, that it sticks in the head and refuses to leave. So too the
best IF puzzles, which keep players wanting to play. The "Lemmings" addiction
stems from the desire to make "just one more attempt" - in the text-game set-up
this corresponds to problems involving complex machinery and with rich feedback
and a lot to fiddle with (such as the machines in "Metamorphoses").
<P>
 You can hook the player whilst no longer at the keyboard, too, with a
different kind of problem. If the goal is clear and the set-up quickly committed
to memory, players can be inadvertently solving - and failing to solve - your
problem as they catch the bus or as they sleep. To construct a good hook, you
need to ensure your puzzle doesn't require too much fiddling about, or
experimentation; and the solution should be intuitive. Mazes do not fit this
category. Perhaps the classic fox-goose-grain-and-boat problem does - but
everyone learns how to solve that at primary school.
<P>
 A good type of puzzle for the player to carry around is the "unfamiliar
object" problem - such as the chipped square in "So Far" or the grey brick in
"Zork II"; which require the player to make a deduction from a small amount of
very relevant information, and possibly through connections with other things
seen before. However, for a puzzle of this type to truly hook the player your
object needs to be intriguing, or the world it is in must be. The mundane is no
good for a hook.
<P>
Sheer Amusement<br>
----------------
<P>
 "The Hitch-Hiker's Guide to the Galaxy", written by Steve Meretzky and
Douglas Adams in 1984, contains numerous puzzles whose sole purpose in the game
is that they're fun. Not fun-to-solve in the brain-bashing sense, but silly,
wacky and downright weird. The experience of solving the best is akin to
producing the punchline of a joke, and I have memories of putting up with all the
difficulties, restarts and dead-ends as a child simply because, when it came down
to it, "WRAP TOWEL ROUND HEAD" was a funny way to avoid a carnivore. The puzzle
of Marvin's door, involving as it does no tea and tea, is a classic.
<P>
 Infocom's games were good for this sort of pay-off. Meretzky's masterpiece,
"Leather Goddesses of Phobos" (1986) contains the infamous T-remover, capable of
producing rabbis and unangling cream; as well as the black paint with which to
turn a white spot into a fully function teleportational black spot. More
recently, Neil DeMause's "The Frenetic Five vs. Mr. Redundancy Man" (1999) had a
side-splitting climactic puzzle.
<P>
 Writers have long known that punctuating a piece with humour is an excellent
way to avoid the tedium of a single atmosphere or situation, and to lessen the
sensation of pretentiousness that monotonic works can quickly attain. Comedy
generally makes the reader more amenable to the writer, and the occasional
well-placed witty puzzle will refresh your player a little and prevent them
becoming too bored or restless. Which bring us to the subject of.
<P>
Rewards<br>
--------
<P>
 We note, to begin with, that puzzles are often hard to solve.
<P>
 Playing "Curses", I found one of its weaker moments to be just after solving
the problem of the garden's hedge maze. This is one of the cleverest puzzles the
game offers; requiring a moment of inspiration followed by a long sequence of
moves in which to implement it. Upon returning to the site of the maze, once
successful, a new location has opened up - but this is not enough reward in
itself, because the location is not very interesting and there is very little in
it, just one object, of no use until very near the end of the game (the stone
rose), and another locked door.  This anticlimax was partly down to the game's
width - the author had no way of knowing at what point in solving all the other,
unrelated, puzzles I would be - but also partly to the assumption that the player
is grateful for any new object. This is not true. Rather, the player - like the
reader of a novel - is rewarded by those things that spark his imagination. It
could be a beautifully rendered location (though this may be unlikely in IF as
players are not often in it for the prose), an empathetic moment, a twist of plot
- but equally it could be a fresh idea on a thorny problem, a ray of hope, a new
object with which to toy in interesting ways and experiment. A player of a game
with puzzles follows both the narrative and the progress of the puzzle-structure
- progress in either is rewarding, but progress in neither is not. A new location
in itself progresses neither, an object with no properties of intrinsic interest
(such as the stone rose) similarly, and the promise of a new puzzle which the
player has no idea how to solve or even start is perhaps actively demoralising.
<P>
 The problem could be alleviated perhaps by a more vigilant game which cheats
to overcome the width problem, providing different objects upon the solution of
problems depending on where in the game the player is. In "The Mulldoon Legacy"
there are four "key" objects  to collected and then used in sequence; but since
the methods of acquiring each are somewhat unrelated the game is careful to
provide the next useful key on solution of any of the four problems: thereby each
time direct progress is made. A similar device could be employed more subtly -
consider a magic-based game in which the spell received on a spell scroll is
tailored to where you are stuck, or a game with money in which the level of pay
received is measured by what you next need to buy. Rewarding the player is one
aspect of design which it is vital to get right, and there is absolutely no
reason not to cheat, if it furthers your goal as an entertainer.
<P>
<P>
IV - Conclusion<br>
================
<P>
 The principles and mechanisms outlined above do not apply solely to
puzzle-oriented games, such as the much-quoted "Curses" and "Christminster".
Rather they are general principles relating to the way players experience the
interaction element of a game. As soon as a player is expected to think about the
effect of their actions and manipulations of the game-world, then the game is
asking for input beyond a simple level, and there needs to be a reward
accordingly. Interactive Fiction works are not game-books, they cannot be plotted
out as simple finite trees, which a computer could step through in optimum time.
But neither are they unaware of their status as simulations and approximations of
both worlds and stories. The balance between the two states is managed by the
players thought process within the world, and so it is the cultivation of that
thought-process which is the mainstay of good design. By asking the player to
think on what he has learnt, you cause the player to paint between fragments of
information and create a continuity and a picture of his own.
<P>
 By being aware of the design decisions taken, the path a player will (most
probably) take, and the way their expectations of the world change as they take
it, an author can make the game far more accessible, far more rewarding and far
more complete than by simply placing ideas into an arena and letting the player
walk around them, poking. 
<p>
Finally<br>
-------
<P>
 To follow T. H. White:
<P>
"What makes a good puzzle?" asked the King.
 
Merlyn chewed his bear a moment and frowned, before finally announcing:
<P>
"To make a good puzzle you need some sort of simulation.
<P>
Around the simulation you need to build feedback-rich experimentation.
<P>
Alongside this experimentation, you need complementary information buried in the
game world.
<P>
Riddled throughout the information should be gaps, patterns and inferences for
the player to speculate upon.
<P>
Amidst the speculation you should give a suggestion of the author's mindset.
<P>
Whilst communicating that mindset, you must be mindful of the rewards of the
eventual solution.
<P>
For the solution you should have a cunning idea."
<P>
Arthur waited a moment to be sure the wizard had finished, then asked:
<P>
"Do any but the last have any relevance at all?"
<P>
Merlyn shook his head.
<P>
"None whatsoever."
<P>
<P>
-- Jon Ingold
<P>