1
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
4
<title>DM4 §50: The design of puzzles</title>
5
<meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1">
6
<link rel="stylesheet" type="text/css" href="dm4.css">
10
<a href="index.html">home</a> /
11
<a href="contents.html">contents</a> /
12
<a href="ch8.html" title="Chapter VIII: The Craft of Adventure">chapter VIII</a> /
13
<a href="s49.html" title="§49: Structure">prev</a> /
14
<a href="s51.html" title="§51: The room description">next</a> /
15
<a href="dm4index.html">index</a>
18
<a id="p392" name="p392"></a>
19
<h2>§50 The design of puzzles</h2>
21
<blockquote>The odyssey of ‘Zork: Mimesis’ begins in a
22
field behind a white house. You climb in through an open window, take
23
the water and sack lunch from the table, go in the living room and move
24
the rug aside to reveal – a blank floor! … Soon the owner
25
of the house – an underemployed, alcoholic bricklayer –
26
is covering you with a shotgun as his unfaithful, neurotic wife dials
27
911. The puzzle-free, super-literary action continues as you are funneled
28
through the criminal justice system…<br>
29
— Roger Giner-Sorolla, conceding that mimesis is not everything</blockquote>
31
<p class="normal"><span class="atleft"><img src="dm4-392_1.jpg" alt=""></span>
32
Without puzzles, or problems, or mechanisms to allow the player to receive
33
the text a little at a time – whichever phrase you prefer –
34
there is no interaction. Inevitably, puzzles are obstacles. Here, Arthur
35
Dent will not be able to meet aliens and have a generally wild time
36
until he has got hold of a babel fish:</p>
38
<p class="output">><tt>examine machine</tt><br>
39
The dispenser is tall, has a button at around eye-level, and says
40
“Babel Fish” in large letters. Anything dispensed would
41
probably come out the slot at around knee-level. It bears a small label
42
which reads “Another fine product of the Sirius Cybernetics
43
Corporation.”<br>
44
><tt>press dispenser button</tt><br>
45
A single babel fish shoots out of the slot. It sails across the room
46
and through a small hole in the wall, just under a metal hook.<br>
47
><tt>remove dressing gown</tt><br>
48
Okay, you're no longer wearing your gown.<br>
49
><tt>hang gown on hook</tt><br>
50
The gown is now hanging from the hook, covering a tiny hole.<br>
51
><tt>push dispenser button</tt><br>
52
A single babel fish shoots out of the slot. It sails across the room
53
and hits the dressing gown. The fish slides down the sleeve of the gown
54
and falls to the floor, vanishing through the grating of a hitherto
56
><tt>put towel over drain</tt><br>
57
The towel completely covers the drain.</p>
59
<p class="normal">(For the final solution, still some way off, see
60
‘The Hitchhiker's Guide To The Galaxy’.) A good game mixes
61
easy puzzles with hard, but no puzzle should be so simple that one obvious
62
command solves it. On the other hand nor should its solution, once
63
guessed, take ridiculously long to achieve, or require endless repetition:
64
such as to fetch something pointlessly distant, or to solve
65
<a id="p393" name="p393"></a>
66
an eight-discs Tower of Hanoi, or to keep juggling objects so that only
67
three are carried at any one time. Here are two basic pitfalls:</p>
69
<div class="clump"><p class="normal"><i>The “Get-X-Use-X” syndrome.</i>
70
By convention, every word or phrase in a cryptic crossword clue is
71
used exactly once to account for some part of the answer. The equivalent
72
in adventure games is the equation “one object = one puzzle solved”,
73
where the player picks up a bicycle pump and looks for a bicycle, picks
74
up a pin and looks for a balloon, and so on. Once used, an object can
75
be dropped, for it surely will not be needed again. But this convention
76
rapidly drains away realism, and most designers try to break the equation
77
in every way possible: with red herrings (one object = no solutions),
78
collection puzzles (many objects = one solution), multiple solutions
79
(any of several objects = one solution) and multiple usages (one object
80
= many solutions).</p></div>
82
<div class="clump"><p class="normal"><i>The “What's-the-Verb”
83
syndrome.</i> In ‘Ballyhoo’, “whip lion”
84
and “hit lion with whip” are inequivalent and only one of
85
them does any taming. The following, from ‘Sorcerer’, can
86
only be called a bug:</p>
88
<p class="output">><tt>unlock journal</tt><br>
89
(with the small key)<br>
90
No spell would help with that!<br>
91
><tt>open journal</tt><br>
92
(with the small key)<br>
93
The journal springs open.</p>
95
<p class="normal">(For a third example, the wording needed to use the
96
brick in ‘Zork II’ is most unfair.) In many games the
97
“examine”, “search” and “look inside”
98
verbs all perform different actions, and it is easy to accidentally design
99
a hidden treasure in such a way that only one of these will find it.
100
(Though at the other extreme, excessive tolerance for verbs leads to
101
everything being “moved”, not “pushed”,
102
“pulled” or “rotated”.) Similarly, in the
103
“What's-the-Noun” syndrome, an object stubbornly fails to
104
respond to reasonable synonyms, such as “sword” for
105
“gladius” or “football” for a soccer ball. But
106
perhaps a remark on a sad subject might be intruded here. The Japanese
107
woman near the start of ‘Trinity’ can be called “yellow”
108
and “Jap”, terms with a grisly resonance. The game shows
109
nothing but respect for her: should it allow the player to do otherwise?</p>
111
<p class="indent">Variety is valuable, but logic
112
and fairness are paramount. “Is the writer pulling a rabbit out
113
of a hat or do you see the fuzzy ears first?” (Dave Lebling).
114
Gareth Rees suggests that one way to ensure that puzzles are consistent
115
with the game containing them is to write a sample transcript of play
118
<a id="p394" name="p394"></a>
119
<blockquote>It stops me coding anything until I have a puzzle fairly
120
well fleshed out in my mind. Too often it's tempting to start coding
121
something one way and then discover that later developments need a
122
different approach.<br>It makes me think like a player (I try to …
123
include a selection of the silly things that I would be liable to type
124
if I were playing the game …). Often when coding it becomes habit
125
just to fail to deal with situations and responses that are tricky to
126
write. Having them appear on the script forces me to say to myself,
127
‘It may be tough to code but it'll appear natural in the game
128
and that's worth it’. I also find it hard to get into the habit
129
of providing interesting responses to failed actions, and the script
130
helps with this.</blockquote>
132
<p class="normal">Another approach is to chain backwards from a goal,
133
repeatedly asking “how can I obstruct this further?”, so
134
that the plot line becomes, like a computer drawing of a fractal curve,
135
more crinkly with each iteration. Peter Killworth, in his book <i>How
136
to Write Adventure Games for the BBC Microcomputer Model B and Acorn
137
Electron</i> (whose opening words are “Adventure games are like
138
avocado pears”) describes an entire game this way
139
(‘Roman’, 1984). Thus you need to pay a debt to a Senator,
140
so you need to steal a bust from a temple, but that means impersonating
141
a priest, by sacrificing a chicken with a gladius, which means catching
142
a chicken (you scare it with a cat, but the cat must be attracted by
143
a mouse, which you need to catch with a mousetrap): and the gladius
144
isn't just lying around, either. You also need a torch, which</p>
146
<blockquote>… needs soaking in oil first, just as candles need
147
wax to burn. So we'd better organise a pool of oil through which the
148
player can walk … When the player gets to a source of flame –
149
how about a brazier of coals, which will have to be untakeable? –
150
he can attempt to light his torch. It isn't oily, it burns to a stump
151
well-nigh instantly … If it is oily, it'll catch fire …
152
No, that's too simple. If a player is soaked in oil too, he'll probably
153
catch fire too! … We'll create a damp, misty area, where the player
154
is assassinated by a runaway slave, unless he enters while on fire.
155
Then he will be safe, because the mist will condense on his body …
156
So the poor player, staggering around and on fire, will try the mist,
157
but to his disappointment the torch will go out permanently too! The
158
solution is trivial – he must drop the torch before entering
159
the mist.</blockquote>
161
<p class="normal">(Killworth's games are not known for their qualms and
162
the player, it will be noted, forfeits the game without any warning
163
by lighting the unoily torch or exploring the misty area.) This kind
164
of plotting, with puzzles strung together like beads onto a necklace,
165
offers the considerable advantage of lending coherency. But it is also
166
liable to make long, linear sequences of puzzles which must be completed
167
in an exact order. “I've found it incredibly hard to keep the
168
puzzles from leading the whole story” (David M. Baggett, 1994).</p></div>
170
<p class="dotbreak">� � � � �</p>
172
<a id="p395" name="p395"></a>
173
<div class="clump"><p class="normal"><i>Mazes.</i> In
174
the <i>Traité des systèmes</i> of 1749, Condillac wrote: “What could be
175
more ridiculous than that men awakening from a profound sleep, and
176
finding themselves in the middle of a labyrinth, should lay down general
177
principles for discovering the way out?” Ridiculous, but very
178
human, because the dogged exploration of a maze is dull indeed, repetitious
179
and irritatingly drawn-out: far more enjoyment is to be found in the
180
working-out of its general principles.</p>
182
<p class="indent">Be it clearly said: it is designers who like mazes
183
(“Concocting such mazes is one of my delights” –
184
Peter Killworth); players do not like mazes. In the original puzzle,
185
a tangled set of rooms have indistinguishable descriptions so that
186
mapping becomes impossible: the original solution is to make the rooms
187
distinguishable again by littering them with objects as markers. This
188
solution is easily obstructed (the ‘Advent’ pirate and
189
the ‘Zork I’ thief wander around picking the objects up
190
again), but this only makes the experience more tiresome. When David
191
Baggett was asked “How do I make my maze so that it doesn't
192
have the standard solution?”, his entire reply was: “Omit
195
<p class="indent">Nevertheless, like the writing of locked-room mysteries,
196
the devising of new solutions for mazes – usually involving guides,
197
or hidden signs, or ways to see – is a modest art form in its
198
own right: novelty being the essential point, though it is equally
199
important to signal to the player that a novel solution exists. The
200
unique <i>The Adventure Gamer's Manual</i> (1992), by the Cornish vicar
201
and eccentric writer Bob Redrup, devotes all of Chapters 7 and 8 to
202
solving maze variants: a faintly weary tone is maintained throughout.
203
Redrup was an aficionado of the Topologika, and thus of the formerly
204
Cambridge University games, which are simply riddled with mazes. Here,
205
in ‘Crobe’ (1986) by the indefatigable maze-maker Jonathan
206
Partington, the player is evidently not expected to explore haphazardly:</p>
208
<p class="output">You are in an underground marsh, a treacherous place
209
where everything looks alike and water and slime lap around your feet.
210
One false move would mean death, but you do at least have the choice
211
of 8 horizontal directions to wander in.</p>
213
<p class="normal">Because lethal unless solved utterly, this is a
214
benign sort of maze. Likewise, in ‘Kingdom of Hamil’ (1982):</p>
216
<p class="output">You are in the Maze of Hamil. Light streams in through
217
many gaps in the rocks. There is the constant sound of rockfalls, distant
218
and not-so-distant.<br>There is a small nickel hexagon here, with
219
the inscription “1 PFENTIME”.</p>
221
<p class="normal">Whatever is going on here, it doesn't look like a
222
simple matter of dropping marker-objects. Partington also has a (thoroughly
223
unfashionable) penchant for elements of randomness which a player can
224
overcome with great difficulty by careful planning. The caryatid maze
225
from ‘Fyleet’ (1985) makes the novel twist of imposing random
226
obstacles on a determined layout, and in ‘The Quest
227
<a id="p396" name="p396"></a>
228
for the Sangraal’ (1987): “There are exits in various directions,
229
but, since the island is rotating, these directions change continually.”
230
Infocom's output has its share of mazes, too, one per game: those
231
in ‘Starcross’ and the ‘Enchanter’, ‘Sorcerer’,
232
‘Spellbreaker’ trilogy are the most satisfying.</p></div>
234
<div class="clump"><p class="normal"><i>Light source puzzles.</i>
235
Almost as disliked, but offering a little more scope to the designer,
236
is the “bringing light to darkness” puzzle. The two standards
237
reduce to refilling a lamp with limited oil and bringing light to a
238
dark room which can apparently only be reached by a player who hasn't
239
got a light source. (‘Advent’ includes both. The lake
240
and aqueduct areas of ‘Zork III’ have an elegant light
241
puzzle, probably the best thing in an otherwise so-so game.) Darkness
242
need not be a problem to be solved, though: it might be a fact of
243
life. Though few games have tried this (but visit the secret passage
244
in ‘Christminster’), a large permanently dark area might
245
still be explored with the other senses.</p></div>
247
<div class="clump"><p class="normal"><i>Capacity and exhaustion puzzles.</i>
248
Again, unpopular because their solution is normally tiresomely repetitive,
249
forcing the player to keep putting things down and picking them up
250
again. It can seem ridiculous that the protagonist can carry hundreds
251
of bulky and fiddly things around all the time, so many designers impose
252
a limit for realism's sake, typically of seven objects. It is bad form
253
to set puzzles making life difficult because the limit is four and not
254
five (after all, in emergency anyone can always carry one more item).
255
In some games the limit is instead on total weight. Taking realism further,
256
some games measure a state of health or even numerical levels of
257
“strength” and “constitution” during play.
258
The protagonist grows hungry and needs food, tired and needs sleep
259
(in ‘Enchanter’ he is positively narcoleptic), wounded
260
and needs recuperation. ‘Planetfall’ simulated a progressive
261
illness whose symptoms are increasing need for food and sleep, and
262
put many players off this kind of puzzle for life. Exhaustion rules
263
are difficult to make fair. A rule requiring a return to an orchard
264
for fruit should be watched carefully, as it will irritate a player
265
to have to do this for a second, a third or a tenth time.</p></div>
267
<div class="clump"><p class="normal"><i>Timed puzzles.</i>
268
Completing this round-up of unpopular but still sometimes justified
269
puzzles are those which involve timed events, running along a script
270
which requires the player to do something specific at one particular
271
moment. In the prologue to ‘The Hitchhiker's Guide To The Galaxy’,
272
why would any player buy the cheese sandwich in the pub and then feed
273
it to the dog in the lane, on the one and only turn in which this is
274
possible? Admittedly, an alternative exists later on, but this is not
275
evident at the time. Mike Roberts (Usenet posting, 1999):</p>
277
<a id="p397" name="p397"></a>
278
<blockquote>Aside from the annoyance, the reason I try to avoid timed
279
puzzles is that they make you acutely aware that you're playing a
280
game. As soon as I get into a save-try-restore loop, any sense of
281
immersion is destroyed for me; I instead feel like I'm debugging a
282
program, since I'm running through a series of inputs to figure out
283
how the game responds.</blockquote>
285
<a id="p397_2" name="p397_2"></a>
286
<p class="normal">This “sense of immersion” can partly be
287
restored by keying events not to game turns but to the time of day,
288
provided this fits the scenario, and making each stage last for a
289
great many more turns than are strictly needed to solve the puzzles.
290
Events which come only to he who waits are also problematic. In the
291
Land of Shadow of ‘Zork III’, only the player who decides
292
for some reason to wait on a fairly uninteresting Ledge will be
293
rewarded with a visitor. (This case is defensible on grounds of context,
294
but only just.)</p></div>
296
<a id="p397_3" name="p397_3"></a>
297
<div class="clump"><p class="normal"><i>Utility objects.</i>
298
A designer who wants players to think of some items as useful needs
299
to provide many situations – more than one, anyway – in
300
which they can be used. A hallmark of better-designed games is that
301
the player accumulates a few useful tools during play and wants to keep
302
them to hand thereafter. (Cf. the crowbar and gloves in ‘The
303
Lurking Horror’.)</p></div>
305
<a id="p397_4" name="p397_4"></a>
306
<div class="clump"><p class="normal"><i>Keys and doors.</i>
307
Almost all games close off segments of the map on a temporary basis
308
by putting them behind locked doors. Many variations on this theme
309
are extant in the literature: coded messages on the door, illusory
310
defences, gate-keepers, the key being in the lock on the wrong side
311
and so on. More usually a locked door signals to the player that a
312
different puzzle (i.e., finding the key) has to be solved before this
313
one can be, so that a designer uses it to impose a chronology on events.
314
Questions to ask here include: if there are people just inside, do
315
they react when the protagonist knocks on the door, or tries to break
316
it down or ram it? Can the door be opened, closed, locked or unlocked
317
from both sides? Are there skeleton or master-keys capable of opening
318
many different doors? Are the keys which do open different doors
319
sufficiently distinctive in appearance? Roger Giner-Sorolla commented
320
that keys are the most naked kind of Get-X-Use-X puzzle:</p>
322
<a id="p397_5" name="p397_5"></a>
323
<blockquote>One can only find so many keys inside fishes' bellies,
324
lost in the wainscotting, dropped at random in corridors, or hanging
325
around guard dogs' necks before the artifice of the puzzle structure
326
becomes painfully clear. By contrast, all six of the keys in
327
‘Christminster’ are hidden in places where one might actually
328
keep a key, and all their locks are guarding places that one would
329
expect to be locked; moreover, we end the game with a pretty clear
330
idea of who normally uses each key and why.</blockquote></div>
332
<a id="p397_6" name="p397_6"></a>
333
<div class="clump"><p class="normal"><i>Machinery and vehicles.</i>
334
Machines are among the easiest puzzles to design: they have levers or
335
ropes to pull, switches to press, cogs to turn. They need not
336
<a id="p398" name="p398"></a>
337
make conversation or respond to anything beyond their function. They often require specialised
338
tools, which brings in objects. They can transform the game in a semi-magical
339
way; time travel or transforming coal to diamond being the clichés.
340
They can also connect together different locations: chains, swinging
341
arms and chutes may run across the map, and help to glue it together.
342
Writing in the TADS manual, Mike Roberts makes the useful point
343
that machines assist interactivity:</p>
345
<blockquote>For example, you might design a machine, described as “a
346
small metal box with a button, a short plastic hose on one side, and
347
a large metal pipe on the other side.” When the button is pushed,
348
“a loud hissing comes from the plastic hose for a moment, then
349
a large drop of clear liquid drops out of the pipe, which hits the
350
floor and quickly evaporates into a white cloud of vapor.” If
351
the player puts the plastic hose in a glass of water and the button
352
is pushed, “the water is sucked into the plastic tube, and few
353
moments later a block of ice is dropped out of the pipe.”
354
This allows the player to learn by experimentation what the machine
355
does, which is more fun for the player than if you had labelled the
356
machine “a freezer” or some such.</blockquote>
358
<p class="normal">In machine puzzles, then, the player experiments with
359
the controls and forms a theory of what is happening. With larger machines
360
this involves visualising the physical construction of the components
361
and how they affect each other: ‘Hollywood Hijinx’ is
362
a tour de force of such puzzles, with a see-saw and a suspended safe.
363
But the literature also includes highly complex self-contained
364
machines presenting something of a black box whose internals must be
365
deduced, such as a B-52 bomber and an Enigma cipher machine
366
(‘Jigsaw’) and a computer which is programmable in the
367
language Scheme (‘Lists and Lists’, Andrew Plotkin, 1996).
368
Vehicles in games to date have included cars, tractors, fork-lift trucks,
369
boats, hot-air balloons, log flumes, punts and elephant rides. Vehicles
370
increase the realism of a landscape, by making it more than a set of
371
rules about walking. They nevertheless need a little care to code:
372
for instance, to disallow driving up ladders or through a narrow crevice.</p></div>
374
<div class="clump"><p class="normal"><i>Fire.</i> The elements
375
all tangle up code but add to the illusion. Fire has many useful properties
376
– it makes light, it destroys things, it can cause explosions and
377
chemical reactions, it cooks food, it softens materials, it can be passed
378
from one object to another – but in the end it spreads, whereas
379
the game's understanding doesn't. If the player is allowed to carry
380
a naked flame, then the game is likely to need a rule to tell it whether
381
or not every other item is flammable, and so on.</p></div>
383
<div class="clump"><p class="normal"><i>Water.</i> In any location
384
where water is available, players will try drinking, swimming, washing,
385
diving. They will try to walk away with, indeed on,
386
<a id="p399" name="p399"></a>
388
make poor objects, because they need to be carried in some container
389
yet can be poured from one to another, and because they are endlessly
390
divisible. “Some water” can easily be made into “some
391
water” and “some water”. If there's more than one
392
liquid in the game, can they be mixed? Pouring liquid over something is
393
likely to make a mess of it: yet why should it be impossible? And so
394
on. The compromise solution is usually to have a bottle with a capacity
395
of, say, 5 units of water, which can be refilled in any room where
396
there is water and so that 1 unit is drunk at a time. The player who
397
tries to pour water over most things is simply admonished and told
398
not to. Implementing swimming, or being underwater, is a different order
399
of difficulty again, and many games agree with ‘Parc’ (John
400
Rennie, 1983) that “since you cannot free yourself, and since
401
you are by nature an air-breathing mammal I'm afraid you drown!”.
402
(Level 9's game ‘Adventure Quest’ is rare in containing
403
a coherently worked out underwater section, though many games have the
404
odd turn's-worth of diving. ‘Jinxter’ (Georgina Sinclair
405
and Michael Bywater, 1987), also has an elaborate underwater section,
406
with a seldom-discovered shipwreck to boot.) What happens to objects
407
being held? Can the protagonist swim while wearing heavy clothes, or
408
carrying many things? Is it possible to dive?</p></div>
410
<div class="clump"><p class="normal"><i>Air.</i> Smoke and
411
fog can obscure the scene, but puzzles involving air are mainly about
412
its absence. The lack of oxygen to breathe has featured in many games,
413
not always through being underwater: ‘Zork I’ and
414
‘Sorcerer’ share a mine with poor air, ‘Starcross’
415
and ‘Trinity’ include locations in the vacuum of space. A
416
scuba mask, space helmet or some other kind of breathing apparatus is
417
called for. (Other gases simulated include helium, explosive hydrogen
418
and laughing gas.) Can the protagonist speak, or eat, or listen, or
419
taste while wearing this apparatus?</p></div>
421
<div class="clump"><p class="normal"><i>Earth.</i> Digging for
422
buried treasure… the shovel can be found in just about every
423
traditional-style game and a good many others which ought to know better
424
besides. The problem is that the player may want to dig anywhere and
425
everywhere, which the game will probably not want to implement: to
426
dig may artificially create a new location, or a new map connection,
427
or a new container – the hole left in the ground, that is. (The
428
prologue to ‘Infidel’, though the least interesting part
429
of the game from the point of view of playing, has a good implementation
430
of digging through sand.)</p></div>
432
<a id="p400" name="p400"></a>
433
<div class="clump"><p class="normal"><i>Plants.</i> Vegetation
434
fits into almost any landscape, and on the grounds of interactivity
435
generally plays some part in the game, which is good for variety, because
436
people deal differently with plants from machines and people.
437
Undergrowth can be pulled away from something obscured, or useful plants
438
picked. Trees and creeping plants ought to be climbable: players nearly
439
always try.</p></div>
441
<div class="clump"><p class="normal"><i>Animals.</i> In many ways
442
preferable to people, animals add a splash of colour, and what would
443
the Garden of Eden have been without elephants, rabbits, leopards and
444
guinea pigs? They move and behave in curious and obsessive ways, displaying
445
what human characteristics they like but not needing to react to conversation
446
or to show human curiosity or surprise at what happens. This makes
447
them much easier to design, but it doesn't exempt them from characterisation.
448
It's a little predictable to make the player feed an animal into obedience
449
and then get it do something. (The bird in ‘Advent’ is nicely
450
characterised, in that it is frightened by the rusty iron rod with a
451
star on one end. ‘Trinity’ is positively overrun with animal
452
life, with some critics having called its roadrunner the most important
453
character.)</p></div>
455
<div class="clump"><p class="normal"><i>Monsters.</i> Many of
456
the early adventure games included trolls, orcs and dragons, or else
457
Frankenstein's Monster, Dracula and vampire bats: some, like ‘Zork
458
I’, allow hack-and-slay combat in the style of a role-playing
459
game like <i>Dungeons and Dragons</i>. Others, like the heavily infested
460
and therefore somewhat repetitive ‘Murdac’ (Jonathan Partington,
461
1982), base all their puzzles on getting past or getting rid of things.
462
“Getting past” occurs often because most monster puzzles are
463
no more than doors with the decoration of slavering fangs. Even when
464
monsters wander, they are generally dull because – being monsters
465
– they have no unpredictable behaviour. Whereas the capacious
466
underworld of the same author's ‘Kingdom of Hamil’ houses
467
a baby hexapod (a what?) and a Conan Doyle-like Lost World of dinosaurs,
468
which is much more the thing.</p></div>
470
<div class="clump"><p class="normal"><i>People.</i> So dawns
471
the sixth day of creation: we have the mountains, rivers, plants and
472
animals, but as yet no people. The nightmare of coding real characters
473
is illustrated well by one of Dave Lebling's example bugs from
474
‘Suspect’ (1984):</p>
476
<p class="output">><tt>show corpse to michael</tt><br>
477
Michael doesn't appear interested.</p>
479
<p class="normal">The body is that of Veronica, Michael's wife. Objects
480
representing people often take extensive code, perhaps five times that
481
needed for even a complicated room, because they may need to react to
482
events, follow instructions (“robot, go
483
<a id="p401" name="p401"></a>
484
south”), wander around the map and make conversation of sorts
485
(the woman selling bread-crumbs in ‘Trinity’, who plays only
486
a minor role, can say over 50 different things). Games with
487
strongly-defined protagonists tend to have a stronger supporting cast, too:</p>
489
<blockquote>‘Christminster’ does an exceptionally good
490
job of outlining Christabel's role as a woman by limiting her actions
491
(she can't enter chapel bareheaded) and through … dialogue (the
492
villains and the Master are condescending, while young Edward sees
493
her as a confidante).</blockquote>
495
<p class="normal">(Roger Giner-Sorolla.) What distinguishes a character
496
from, say, a spanner is that it has an attitude to the protagonist. One
497
model of this has the current attitude as a position in a “mood
498
maze”, with different moods being like locations and stimuli
499
applied by the protagonist being like directions:</p>
501
<p class="lynxonly"></p>
502
<table align="center" class="objtree">
503
<tr><td>Suspicious</td><td colspan="2" rowspan="2"></td></tr>
504
<tr><td><small style="color:white"><i>reassure</i></small>↓<small><i>reassure</i></small></td></tr>
505
<tr><td rowspan="2">Hungry</td>
506
<td><small><i>feed</i></small></td>
507
<td rowspan="2">Grateful</td></tr>
508
<tr><td>→</td></table>
510
<p class="normal">(Setting out in the “feed” direction from
511
Suspicious leads nowhere, as the food is not accepted.) Such a person
512
is no more than a plaything, entirely reactive and without memory, so
513
most designers would want to conceal this fact by adding spontaneous or
514
even random behaviour, startling the player from time to time. Or,
515
of course, by simulating some memory of events. Adam Cadre's ‘Varicella’
516
(1999) handles conversation using around 450 flag variables to remember
517
which questions have been asked and answered before. It also reformulates
518
conversation. Here, the protagonist Varicella – as bad as the
519
rest of them, Cadre having a rare gift for the amoral – encounters
520
Miss Sierra, the King's mistress:</p>
522
<p class="output">><tt>ask sierra about king</tt><br>
523
“What can you tell me about the King?” you ask. ”You
524
seem to have known him better than anyone else…”<br>
525
Miss Sierra scowls at you. “That had better not be an attempt at a
526
personal question,” she says. “If you're expecting a rhapsody
527
about how he won my girlish heart, think again.…”<br>
528
><tt>ask sierra about king</tt><br>
529
“Is there anything else you care to say about the King?”
532
<p class="normal">Elsewhere, “ask guard about rico” can
533
come out as “Is Rico in?”, “ask queen about prince”
534
as “How is Prince Charles?” and so on according to what
535
would make sense in context. Such programming is exhausting but fruitful
536
in a game placing great reliance on conversation.</p></div>
538
<a id="p402" name="p402"></a>
539
<div class="clump"><p class="normal"><i>Ropes and chains.</i>
540
Are notoriously troublesome to implement consistently:</p>
542
<blockquote>[Someone will] say “Well, I've got this rope…
543
how do I do a rope? It can be in two rooms at once if you tie it to
544
something and take the end with you, and can you tie things up with
545
it and drag them around with you?”<br>
546
Then we'll stop and think and say, “You don't want to have a
547
rope in your game,” and that makes it much easier for the new
548
writers, you see.<br>
549
My new game [‘The Lurking Horror’] has a chain in it, and
550
it's even worse than a rope in almost every respect you can imagine
551
and it's caused me no end of horror… the number of bugs that
552
have come in on this chain alone would stack from here to there and
553
back again.</blockquote>
555
<p class="normal">(Dave Lebling again. But the chain puzzle in
556
‘Lurking’ is a masterstroke.) ‘The Meteor, The Stone
557
and a Long Glass of Sherbet’ has a rope solving several puzzles
558
whose source code runs to 300 lines of Inform, which is more than
559
the whole “lily pond” region took: put another way, 5%
560
of the entire code is occupied describing the rope. There is also a
561
long ladder which is nearly as bad, and which the player is not allowed
562
to tie the rope to.</p></div>
564
<div class="clump"><p class="normal"><i>Riddles.</i> Numerous
565
games (‘Beyond Zork’, ‘The Path to Fortune’ (Jeff
566
Cassidy and C. E. Forman, 1995)) include sphinxes or talking doors
567
which pose riddles to passing strangers, and the writing of good riddles
568
is an art form in itself. But who put these puzzle-obsessed doorkeepers
569
there, and why? The knock-knock joke door in Irene Callaci's ‘Mother
570
Loose’ (1998) sits much more happily, as the game is a wry mingling
571
of nursery-rhyme stories for her six-year-old granddaughter (and indeed
572
for the rest of us).</p></div>
574
<div class="clump"><p class="normal"><i>Decipherment.</i>
575
Perhaps the most abstract and, if done well, the most satisfying of
576
puzzles are those which present a system of coded messages, clues to
577
the meaning of which are scattered across the game. ‘Infidel’
578
has hieroglyphics. ‘Edifice’ (Lucian Smith, 1997) requires
579
the player to learn the language of Nalian, a puzzle which won considerable
580
plaudits from players. But there are non-linguistic decipherments,
581
too: in a sense the map of ‘Spellbreaker’ is itself a
582
cipher. On a smaller scale, several Cambridge University games contain
583
tricky cipher puzzles not unrelated to recreational mathematics.
584
‘Avon’, for instance, has a substitution code which is
585
insoluble, but which it is possible to make partial deductions about:
586
just enough to solve the problem at hand.</p></div>
588
<p class="dotbreak">� � � � �</p>
590
<div class="clump"><p class="normal"><i>Clues.</i> At least in
591
one view of interactive fiction, clues are essential and the principle
592
should be that an ideally perceptive player could win on his or her
593
first attempt, without recourse to saved games: in particular, without
594
knowledge of past lives or of future events. (The exact opposite, in
595
fact, of what ‘Brand
596
<a id="p403" name="p403"></a>
597
X’ does. The player begins in a shop
598
containing an aqualung, a cushion, a bunch of keys, a piece of sausage,
599
a teabag and a sign declaring that “only two implements may
600
be removed from this shop under penalty of death, so choose carefully”.)
601
Here are three clues which did not carry:</p>
603
<ol style="list-style-type:decimal">
604
<li>In ‘Dungeon Adventure’, a pride of lions is carved
605
over a doorway. Any player walking through falls into a lethal pit.
606
Did you miss the clue?<a id="s50_fnref1"
607
name="s50_fnref1"></a><a href="#s50_fn1">†</a></li>
608
<li>The diamond maze in ‘Zork II’ is almost impossible to
609
fathom unless (or even if) you are familiar with a certain multiple-innings
610
team sport played only in America. In the words of even its designer:
611
“always annoyed me… pretty lame.”</li>
612
<li>Almost every player of ‘Advent’ has considered the
613
rock marked Y2 to be a decoy, emblematic of the mysterious cave. But
614
it was meant as a clue: on the cave maps used by Will Crowther's group,
615
“Y2” denoted a secondary cave entrance, which in a certain
616
sense is what this location is.<a id="s50_fnref2"
617
name="s50_fnref2"></a><a href="#s50_fn2">‡</a></li>
620
<p class="normal">(1) is a bad pun, (2) an unconscious assumption and
621
(3) an in-joke. Games that are entirely in-jokes, like the subgenre
622
of college campus simulations (‘The Lurking Horror’ features
623
MIT, Infocom's alma mater) are at least deliberately so, but it is
624
all too easy for designers to include familiar objects from their own
625
lives into any game, and unconsciously assume that the player shares
626
this familiarity. When that familiarity is needed to solve a puzzle,
627
the game may become unplayable.</p></div>
629
<div class="clump"><p class="normal"><i>Luck and accidental solutions.</i>
630
Small chance variations add to the fun, but only small ones.
631
The thief in ‘Zork I’ seems to me to be just about right
632
in this respect, and similarly the spinning room in ‘Zork II’,
633
but a ten-ton weight which falls down and kills the player at a certain
634
point in half of all games would simply irritate. A particular danger
635
occurs with low-probability events, one or a combination of which might
636
destroy the player's chances. For instance, in the earliest edition
637
of ‘Adventureland’, the bees have an 8% chance of suffocation
638
each turn carried in the bottle: one needs to carry them for 10 or 11
639
turns, giving the bees only a 40% chance of surviving to their
642
<p class="indent">Even in a puzzle with no element of luck, many problems
643
are solved by accident or trial and error. (The notorious Bank of Zork
644
puzzle in ‘Zork II’ has been understood by almost nobody
645
who solved it.) This is unsatisfying for
646
<a id="p404" name="p404"></a>
647
both player and designer, and
648
some games take steps to try to avoid it. The gold-assaying puzzle
649
in ‘Spellbreaker’ is such that a shrewd strategy will always
650
succeed, but in principle even a random strategy <i>might</i> succeed.
651
The game rigs the odds to ensure that it never does.</p></div>
653
<div class="clump"><p class="normal"><i>Optional, partial and multiple
654
solutions.</i> Most designers like to give two or more different
655
solutions to a few puzzles in a game: it seems more real, it means that
656
even a winning player hasn't found all of the game's secrets and it
657
makes a difficult puzzle easier. (There are seven ways to open the
658
child-proof medicine bottle in ‘Curses’.) Multiple solutions
659
to the same puzzle need to be equally valid. The designer should not
660
think of one solution as the “real” one, or allow another
661
“short cut” one to skip critical plot events – this
662
would short-change the player. On the other hand the designer must
663
be relaxed about the inevitability that some part of his golden prose
664
will never be seen whichever path the player takes. Most additional
665
solutions are added in play-testing, but here is Brian Moriarty
666
on ‘Wishbringer’ (1985):</p>
668
<blockquote>Most of the problems in the story have two or more solutions.
669
The easy way out is to use Wishbringer. If a beginner gets frustrated,
670
he can whip out the magic stone, mumble a wish and keep on playing.
671
Experienced players can search for one of the logical solutions –
672
a bit harder, perhaps, but more satisfying. It's possible to complete
673
the story without using any of the stone's seven wishes. In fact, that's
674
the only way to earn the full 100 points.<br>The puzzles are highly
675
interconnected. Once you start wishing your problems away, it's
676
very hard to continue playing without relying more and more on the
677
magic stone. The impotence of idle wishing – that's the moral
678
of ‘Wishbringer’. All really good stories have a moral.</blockquote>
680
<p class="normal">Analogous perhaps to the Wishbringer stone, ‘Enchanter’
681
has a one-use-only anti-magic spell. Although this solves one in particular
682
of the more difficult puzzles, to use it up so early forfeits the game,
683
since it is needed later. If you do fall into this trap, one of the ingenious
684
dream sequences offers an oblique warning:</p>
686
<p class="output">You dream of climbing in an unfamiliar place. You
687
seem to climb forever, beyond reason. A fleeting hope arises in you,
688
and you search furiously in your spell book and possessions for something.
689
After a moment, you become frantic as you realize that you don't have
690
it! You bolt awake in a cold sweat.</p></div>
692
<div class="clump"><p class="normal"><i>Rewards.</i> What reward
693
for solving a puzzle? One is obvious: the game state advances a little
694
towards its completion. But the player at the keyboard needs a reward
695
as well: that the game should offer something new to look at. The
696
white cubes in ‘Spellbreaker’, with the power to teleport
697
the protagonist to new areas, are far more alluring than, say, the
698
“platinum pyramid” of ‘Advent’, which is only
699
a noun with a few points attached and opens up no further map.</p></div>
701
<a id="p405" name="p405"></a>
702
<p class="aside"><span class="warning"><b>•</b>
703
<b>REFERENCES</b></span><br>
704
“[A puzzle] should be logical, according to the logic of the
705
game's universe. In a fantasy game, a puzzle can rely on magic, but
706
the magic must be consistent throughout the game. A puzzle should be
707
original in some way, not just a rehash of an earlier puzzle with different
708
objects.” (Steve Meretzky). “My basic principle of designing
709
puzzles is that the player should always know what he's trying to accomplish.
710
Metaphorically, a player should always be able to find a locked door
711
before he finds the key” (Mike Roberts in the <i>TADS</i> manual).
712
“In all cases, after a particularly arduous puzzle, reward the
713
player with a few simpler ones” (C. E. Forman, <i>XYZZYnews</i>
714
1). “Err on the side of easy. (He said, waiting to be struck
715
dead for hypocrisy.)” (Andrew Plotkin). “There's definitely
716
a difference between ‘satisfying’ and ‘pertinent’.”
717
(Lucian Smith. These last quotations from the round-table discussion
718
on puzzles in <i>XYZZYnews</i> 14.)
719
<span class="warning"><b>•</b></span>For more on the invented language
720
in ‘Edifice’, see ‘Parlez-Vous Nalian’ in
721
<i>XYZZYnews</i> 16.</p>
723
<hr class="footnotebar">
724
<p class="aside" style="margin-top:0"><a id="s50_fn1"
725
name="s50_fn1"></a><a href="#s50_fnref1">†</a>
726
Pride comes before a fall.</p>
728
<p class="aside"><a id="s50_fn2"
729
name="s50_fn2"></a><a href="#s50_fnref2">‡</a>
730
Several Cambridge University games, written
731
by mathematicians, refer to “J4”: ‘Acheton’,
732
for instance, has a “J4 room” rather like the “Y2
733
rock room”. The then-recent construction of the previously only
734
hypothetical group <i>J</i><sub>4</sub> had completed the classification
735
theorem for finite simple groups, and was a departmental triumph.
736
The sign “∃<i>J</i><sub>4</sub>” remained above a doorframe
741
<a href="index.html">home</a> /
742
<a href="contents.html">contents</a> /
743
<a href="ch8.html" title="Chapter VIII: The Craft of Adventure">chapter VIII</a> /
744
<a href="s49.html" title="§49: Structure">prev</a> /
745
<a href="s51.html" title="§51: The room description">next</a> /
746
<a href="dm4index.html">index</a>
added
removed
inform-6.31.1/manual/s50.html
