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<title>DM4 §49: Structure</title>
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<h2>§49 Structure</h2>
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<p class="normal"><span class="atleft"><img src="dm4-378_1.jpg" alt=""></span>
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Games from all of the major design houses of the 1980s share a common
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structure, partly because they were planned as if they were Hollywood
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films, which even today retain the shape of a three-act play from
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nineteenth-century theatre. Designers would begin by making a formal
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pitch, writing two or three-page synopses of the action, and serious
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coding did not begin until such a synopsis had been talked through.
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Structural breakdowns of what they produced are often revealing.</p>
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<p class="dotbreak">� � � � �</p>
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<p class="normal"><i>Size and density.</i>
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There was a time when the sole measure of quality in advertisements
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for cheaper adventure games was the number of rooms. Level 9's most
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original work, ‘Snowball’, claimed to have over 7,000
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locations, of which 6,800 made up an unusually wearisome maze. Even
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a 200-room game meant only minimal room descriptions and simple puzzles,
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scattered thinly over the map. Whereas ten of the Infocom games have
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fewer than sixty rooms, with ‘Seastalker’ (30 rooms),
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‘The Witness’ (30) and ‘The Hitchhiker's Guide
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To The Galaxy’ (31) the most geographically concise. Today's
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custom is that, barring a few junctions and corridors, there should
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be something interactive in every room.</p>
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<p class="indent">Today's design systems impose few restrictions on
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game size or construction, but designers still have an unconscious idea
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of a “budget” for a game design, if only to keep its
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proportions in balance. A typical medium-to-large game contains
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250 objects, counting items, rooms and other sundries (the player,
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the compass directions) as objects. Many items are not portable but
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are instead walls, tapestries, thrones, control panels, coal-grinding
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machines and, as a rule of thumb, three items to one room is about right.
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We might therefore expect 60 rooms, and the next step in budgeting would
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be to share these out among game regions. The 180 or so items might divide
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as 50 portable items and 130 furnishings. (‘Wishbringer’:
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250 objects, 52 rooms, 34 takeable items.) As for the text, ‘Enchanter’
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contains 20,100 words, ‘Trinity’ 32,200 and ‘Curses’
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44,000, but the latter are large games and 25,000 words is more typical:
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around a quarter of the length of a typical novel, for an average of
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only 400 words per location. The size of the source code varies dramatically
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with the design system, but for instance: ‘Spellbreaker’
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17,800 lines, ‘Christminster’ 13,000, ‘Once and
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Future’ (Gerry Kevin Wilson, 1998) 35,000.</p>
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<a id="p386" name="p386"></a>
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<p class="indent">Limitations can be a blessing in disguise, because
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they force a designer to keep asking if this part or that part is
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altogether necessary. Here is Brian Moriarty, whose research went
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as far as looking up geological surveys:</p>
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<blockquote>The first thing I did was sit down and make a map of the
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Trinity site. It was changed about 50 times trying to simplify it
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and get it down from over 100 rooms to the 40 or so rooms that now
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comprise it. It was a lot more accurate and very detailed, but a
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lot of that detail was totally useless.</blockquote>
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<p class="normal">This reduction to 40 rooms would have been worthwhile
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even if memory and disc space had been unlimited. Redundant locations
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can be an indication of too much prose and too little interaction.
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‘The Light: Shelby's Addendum’ (C. A. McCarthy, 1995)
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contains much that is praiseworthy but its reviewers took a dim view
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of its having over twenty locations in which nothing happens.</p>
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<p class="aside"><span class="warning">▲</span>
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It is not always realised how technical constraints have influenced the
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literary style of the classic games, and so of what we consider to
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be good today. Infocom's writers were mostly working under an absolute
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ceiling of 255 objects (including rooms) and memory was more pressing
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still. Lebling summarised the implementor's frustration <i>en passant</i>
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in a 1987 memo: “I made a pitch for a more-unlimited game system…
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Brian [Moriarty] is already running out of table space in his game, Amy
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[Briggs]'s game is too big and not even in Beta yet, all our EZIP games
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have had to be cut, and ‘Bureaucracy’ [Douglas Adams, 1987]
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had to become EZIP instead of LZIP.” (We would now call both
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EZIP and LZIP version 4 of the Z-machine, but LZIP games were small
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enough to run on a Commodore 64 – the biggest source of sales
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– and EZIPs weren't.) Lebling lamented in 1998 that “a lot
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of lovely shivers” had to be cut out of his almost-finished
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‘The Lurking Horror’ as a result: whereas in spite of
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the amount of her game (‘Plundered Hearts’) that ended
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on the cutting-room floor, Amy Briggs felt that “The constraints
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of running on the Commodore 64 helped the games be richer, I believe,
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than if we had been writing then for the Pentium Pro”
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(<i>XYZZYnews</i> 12). Similarly, Scott Adams's games, running on
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smaller computers with tape decks instead of disc drives, were obliged
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to show extreme economy with objects and textual messages, but
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coded rules and what we would now call daemons so efficiently that these
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few objects ended up tightly interlinked, with side effects and multiple
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<p class="dotbreak">� � � � �</p>
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<p class="normal"><i>The prologue.</i> Most games divide into
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three phases: prologue, middle game and end game. These phases are
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often closed off from each other, so that once a phase has ended it
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cannot be returned to, though the prologue sometimes offers premonitions
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of the end, or conversely the end game echoes back to the prologue.
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Like the children in C. S. Lewis's tales of Narnia, the player is
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always going “further up, and further in”. Stu Galley, in
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debugging the mystery ‘The Witness’, found himself obliged
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to enforce the plotting of the passage between prologue and middle
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<a id="p387" name="p387"></a>
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<blockquote>[The play-testers] discovered significant “branches”
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in the story that I had overlooked. For example, what if the player sneaks
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into the house or doesn't go in at all until too late? The first possibility
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raised too many complications, so we decided to lock all the outside doors.</blockquote>
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<p class="normal">The duties of the prologue are to establish an atmosphere,
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to foreshadow what is to come and give out a little background information,
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while giving the player enough entertainment to want to continue. The
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interactive aspect of this is that the player has to pick up the game's
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special skills, using commands, tools or actions special to the setting.
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(The prologue to ‘The Meteor, The Stone and a Long Glass of Sherbet’
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(Angela M. Horns, 1997) uses an easy puzzle involving a telescope and
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a guide book to provide practice with them.)</p>
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<p class="indent">The task of passing into the middle game should be
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reasonably straightforward, but at the same time involved enough that
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the player has a feeling that time spent on the game is time rewarded.
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The designer would be wise to imagine that the player of the prologue
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is really only toying with the game at this stage, and isn't drawing
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a map or being at all careful. If the prologue is too big, the player
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will quickly get lost and give up. If it is too hard, then many players
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simply won't reach the middle game.</p>
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<p class="aside"><span class="warning">▲</span>
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The passage from the prologue to the middle game is often also the passage
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from the mundane to the fantastical, so that the prologue answers the
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question “How did I get into all this?” The prologue of
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‘Advent’ is an above-ground landscape, whose presence
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lends a much greater sense of claustrophobia and depth to the underground
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bulk of the game. On the other hand, a few games drop the player right
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in at the deep end, as in ‘Plundered Hearts’, which opens
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to a sea battle in full swing.</p>
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<p class="aside"><span class="warning">▲</span>
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Notable prologues include the streets and meadows outside the apparently
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impenetrable ‘Christminster’ college (4 locations), the
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undemolished planet Earth of ‘The Hitchhiker's Guide To The
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Galaxy’ (6) or 221B Baker Street in ‘Sherlock’ (again,
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6), but some have been as large as the guild house of ‘Sorcerer’
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(Steve Meretzky, 1984), at 13 locations, or the seaport of ‘Crobe’
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(Jonathan Partington, 1986), at 18. ‘Advent’ in its classical
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form had an 8-location prologue, but some extensions (such as Level
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9's) fleshed out the above-ground substantially, making the volcano
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visible as a precursor to its underground discovery late in the
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<p class="dotbreak">� � � � �</p>
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<p class="normal"><i>The middle game.</i> The middle game is
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the one which least needs detailed planning in advance, because it
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is the one which comes nearest to being a miscellaneous collection
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of puzzles. On the other hand, since it is also the largest part
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it is the most in need of some rough subdivision into segments.
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Working through these segments, one by one, provides a sequence of
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problems and rewards for the player. A first-draft design of the middle game may just
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<a id="p388" name="p388"></a>
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consist of a rough sketch of these segments,
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with some general ideas for objects, places and characters. Slotting
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actual puzzles in can come later in a more improvisatory, freewheeling
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<p class="indent">The obvious way to subdivide is to carve up the
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map, perhaps with a pattern to the regions, perhaps even sharing regions
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out to different authors (as in the AGT game, ‘Shades of Gray’,
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1993). Regions correspond perhaps to time zones, to the four winds
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or the twelve signs of the Zodiac, or else are delineated from each
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other through simple geography: cave games are especially prone to
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this, often having a node-like room with exits in all eight cardinal
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directions. Thus ‘Zork II’ (Marc Blank and Dave Lebling,
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1981) has seven areas arranged at compass points around the Carousel
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Room, with the area northeast serving as prologue. Sometimes the
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same locale occurs more than once, revisited with a different perspective.
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The innovative ‘Spider and Web’ (Andrew Plotkin, 1998),
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in which a player is being interrogated about what really happened
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when a secret installation was broken into, features repeated but
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varying hypothetical versions set in the same locations.</p>
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<p class="indent">Other designers structure the game around performances:
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in ‘Ballyhoo’ the player enacts the full repertoire of
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circus skills, and in a region of ‘The Quest for the Sangraal’
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all seven deadly sins must be committed. More often, though, dramatic
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actions are intended to become the turning points in a story. Gareth
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Rees (in <i>XYZZYnews</i> 6):</p>
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<blockquote>In ‘Christminster’, I identified a set of key
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scenes each of which was an event or experience that affected the
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player character, and moved the story forwards towards the conclusion,
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and yet could plausibly be implemented as a section of an adventure
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<p class="normal">In chronological terms, the plot literally moved
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forwards: the clock, in ‘Christminster’, chimes the half-hour
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when a key event takes place, advancing towards dinner in hall, but
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time hangs heavy in an endless Cambridge afternoon while the player
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is stuck. Puzzles were slotted in later, often around the needs of
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the plot. One of the game's most enjoyable sequences, with the player
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exploring a pitch-dark secret tunnel in the company of Professor Wilderspin,
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in fact exists only to oblige the player to spend time in the Professor's
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company so that he can do a good deal of talking. Like most traditional
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interactive fiction, ‘Christminster’ has a plot with little
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overall variation except for the order in which the player does things.
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But some radical designers see events not as milestones but forks in
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the plot. Thomas M. Disch:</p>
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<blockquote>… any computer-interactive text deconstructs itself
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as you write because it's always stopping and starting and branching off
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this way and that … With ‘Amnesia’, I found myself
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working with a form that allowed me to display these erasures,
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these unfollowed paths.</blockquote>
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<a id="p389" name="p389"></a>
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<p class="normal">There are games, though, in which an entirely improvised
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middle game is compensated for by a tautly controlled prologue and
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end game. Andrew Plotkin (in <i>XYZZYnews</i> 14):</p>
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<blockquote>Since ‘So Far’ [1996] is pretty much pure
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surrealism, I didn't have a plot in mind originally. I had a theme,
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and was co-inventing puzzles and scenes and events all at the same
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<p class="normal">This sounds potentially shambolic, but in an interview
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(<i>XYZZYnews</i> 13) in the immediate aftermath of testing ‘So Far’,
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Michael Kinyon found it enormously affecting. Steve Meretzky:</p>
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<blockquote>Sometimes you have only a sketchy outline and are just beginning
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to coalesce the geography. Sometimes the geography coalesces around the
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puzzles. Sometimes it's both together.</blockquote>
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<p class="normal">Geography coalescing around puzzles is evident in
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Meretzky's work, in which events often spread across multiple locations,
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as in the case of the ‘Sorcerer’ flume ride.</p>
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<p class="aside"><span class="warning">▲</span>
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The middle game is likely to have the largest area of playable map that
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the player will face. In laying this out, it adds to the interest to
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make connections in the half-cardinal compass directions – northeast,
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northwest, southeast, southwest – and to steer away from a feeling
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that the game has a square grid. (One of the few defects of the
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‘Trinity’ middle game, though possibly that was the price
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to be paid for one of its better puzzles.) Equally, a few, possibly long,
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loops which can be walked around reduce retracing of steps and avoid
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the appearance of a bus service map in which half a dozen lines have
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only one exchange.</p>
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<p class="aside"><span class="warning">▲</span>
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The passage from middle game to end game often takes the form of a scavenger
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hunt: throughout the middle game a number of well-hidden objects are
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collected and only when they are combined can the end game be entered. See
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‘Lords of Time’ (Sue Gazzard, 1983) or indeed almost any game
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produced in the wake of ‘Advent’, as it was almost taken
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for granted that any game must have “treasures”. Soon
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enough it became a cliché, and one which games like ‘Leather
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Goddesses of Phobos’ or ‘Hollywood Hijinx’
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(“Hollywood” Dave Anderson and Liz Cyr-Jones, 1986) send
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up, but it's still not a bad idea, because it enables many different
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problems to be open at once. You can be stuck finding sprocket 2 and
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go and work on finding sprocket 5 for a while instead.</p>
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<p class="dotbreak">� � � � �</p>
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<p class="normal"><i>End game.</i> End games serve two purposes.
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First, they give the player a sense of being near to success (they used
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to be called the “Master Game”), and can be used to culminate
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the plot, to reveal the game's secrets. They also serve to stop the
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final stage of the game from being too hard to play, narrowing it to
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only a few accessible rooms or objects. In cave games like ‘Zork’,
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the final puzzle would be made exceptionally difficult but today's designers
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<a id="p390" name="p390"></a>
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usually prefer to give the player the satisfaction of finishing,
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and themselves the satisfaction of knowing that their story has been
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<p class="indent">A mark of the last pieces of the puzzle falling into
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place is that loose ends are tied neatly up and the characters sent
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away with their fates worked out and futures settled. Looking back,
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from the point of view of a winning player, can you understand what
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has happened and why? Can you also see what is to happen to the protagonist
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<p class="indent">The final message is another important one and, as
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with the overture, the coda is all the better for being brief. To quote
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examples would only spoil their games. A popular device is to make
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the two scenes which open and close the story “book-ends”
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for each other, symmetrical and matching.</p>
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<p class="aside"><span class="warning">▲</span>
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To speak of “the” final message or “the” last
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step is a little presumptive. Multiple outcomes are not to every designer's
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taste, but Daniel Ravipinto's ‘Tapestry’ (1996), with
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its sense of tragedy, and its misleading portents and advice, drew
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much of its strength from an open end. (Its plot owes much to the 1993
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<i>Star Trek: The Next Generation</i> episode of the same name.)</p>
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<p class="aside"><span class="warning">▲</span>
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Gerry Kevin Wilson suggests that the end game should feature “your
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Big Nasty™. The Big Nasty™ is the final challenge, be it monster,
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man, maze, or whatever. This is where you want to ham up your writing
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and get a sense of urgency going. There needs to be a time limit…”
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In this view, which is not universally shared, the end game is like
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a video game's “Boss Level”.</p>
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<p class="aside"><span class="warning">▲</span>
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Like prologues, end games vary in size: from a one or two location single
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closing scene (‘The Lurking Horror’, ‘Sorcerer’)
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to a new game region (the Dungeon Master's lair in ‘Zork III’
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(Marc Blank and Dave Lebling, 1982), 7 locations, or Roman Britain in
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‘Curses’, 16).</p>
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<p class="dotbreak">� � � � �</p>
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<p class="normal">Games in the style of ‘Advent’ are very
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wide, with around thirty or so puzzles, all easily available and soluble
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in any order. Others, such as the Melbourne House adaptation of Tolkien
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(‘Lord of the Rings Game One’ (later a.k.a. ‘The
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Fellowship of the Ring’), ‘Shadows of Mordor’, ‘The
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Crack of Doom’, Philip Mitchell, 1985, 1987, 1989), are very
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narrow: a long sequence of puzzles, each of which leads only to a
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chance to solve the next. Wide games are dull, since no problem solved
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will lead to any radical change. Narrow games are difficult to pitch:
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if the one puzzle open at a time is easy then play is too rapid, but
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if it is hard then the player will be abruptly slammed into a wall
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<p class="indent">Towards the end of design it can be helpful to draw
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out a lattice diagram of the puzzles. At the top is a node representing
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the start of the game, and then lower nodes represent solved puzzles.
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An arrow is drawn between two puzzles if one has to be solved before
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the other can be. Here is the lattice diagram for
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<a id="p391" name="p391"></a>
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‘Ruins’, with subscripted numbers showing the points scored on reaching each
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given position: each of the artifacts is worth 5 except the jade mask,
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worth 10. [<a href="colophon.html#ld_lattice">description</a>]</p>
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<p><img src="dm4-391_1.jpg" longdesc="colophon.html#ld_lattice"
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title="Lattice diagram for ‘Ruins’"
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alt="The diagram is simple, but balanced, showing which puzzles are
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prerequisites for solving other puzzles, from the start to the end of
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the game. It also shows that for most of the game, the player has at most
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two puzzles to work on, and at three points in the game, only one."></p>
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<p class="normal">This diagram is useful for three reasons. Firstly,
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it checks that the game is soluble at all: for example, if the jade
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mask had been kept in Xibalbá, there would be no solution.
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Secondly, it shows how much of the game happens in different areas.
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Most usefully of all, the diagram shows whether the game is wide or
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narrow and which puzzles are likely to be bottlenecks, with large
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parts of the game depending on their solution. This tall, spindly
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diagram is indicative of a fairly linear plot, not surprisingly as
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the game is so small. The problem of entering the Shrine is evidently
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<p class="aside"><span class="warning">▲</span>
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A long arrow on a lattice diagram is a caution that some action very
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early in play is essential even though it has no effect until some
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other action much later on. If the early action becomes impossible
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later, for instance because it is in a prologue which cannot be returned
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to, the player will legitimately feel aggrieved. In ‘Christminster’,
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“getting invited to dinner” is theoretically an early puzzle
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because access to the Master's lodgings occurs at the outset of the
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middle game, but the puzzle never goes away and remains accessible
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right up to dinner time.</p>
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<p class="aside"><span class="warning"><b>•</b>
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<b>REFERENCES</b></span><br>
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C. E. Forman exhibits the lattice diagram for ‘Enchanter’,
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which clearly shows its prologue, middle game, end game structure, in
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<i>XYZZYnews</i> 4. Replying in issue 6, Gareth Rees argues that game
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analysis is an aid to, rather than an integral part of, game design.</p>
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