Tag: mapping

RPG-ology #31: Screen Wrap

This is RPG-ology #31:  Screen Wrap, for June 2020.


This was originally published on June 29, 2001, at Gaming Outpost, as Game Ideas Unlimited:  Screen Wrap.

I usually call it “recursive occlusion”; but that’s because that’s what Peter Davison’s Doctor called it in Castrovalva, and now that I get around to thinking about what that means he must have been referring to the method of construction—that the Master had built a trap for him by creating a world based on a formula in which each element was dependent on all previous elements, resulting in a blockage of all exits.  But that’s not important.  The idea is a lot simpler than that.

Years ago there was a video game called Tank.  Tanks would wander around the screen trying to shoot each other.  Thing was, in the early versions you could shoot off the top of the screen and the bullet would come in at the bottom; or you could shoot off one end and have it come in the other.  In some versions you could actually drive the tank that way, off one side and on the other.  It wasn’t the only game that did that, and it was a simple solution to a basic problem:  what do you do about the boundaries?

But it’s an idea I’ve used many times to mystify and confuse my players—and in more variations than you might have imagined.  But if you’ll come with me for a moment, I’ll try to help you imagine a few.

The first one’s easy.  The characters enter some sort of complex—a section of tunnels in a dungeon, an area of rooms and hallways in a space station.  As they pass a certain point, they are inside the boxThe box is clearly marked on your map—it shows that any exits to the east connect to those to the west, and those in the north run to those in the south.  If a character walks into that last ten-foot section on the edge of the box, he’s immediately teleported to the first ten foot section on the other side, so going out one side means coming in the other.  Only one of the entrances is also an exit.  You will be surprised at how many times the players will redraw the same configuration of tunnels before they realize that something is amiss.

The second variation takes the idea to another level.  I did this to one player once, and I’m not sure he figured it out even after someone explained it to him.  I put the same room in two different places on the map.  I denoted them with subscripts so I could keep them straight.  Because they were the same room, if you entered the room, you were in both places at once; but when you exited the room, you always left from the other one.  They weren’t far apart in this experiment—which actually added to the confusion, as he entered the first, left the second and walked back to the first, and drew it twice, but in the wrong position.  At one point part of the party left the room and came back, and then when they all left together they got split up, because some had entered the first room and some the second, but they all were together whenever they were in the room.

You could use this idea to move characters very long distances—another dungeon, another space station, another planet.  You don’t even really need the rooms—you can just use some innocuous looking door.  Looking through the door, you see another room; step through the door, you’re in a room that looks just like the one you saw, but isn’t it.

These ideas have basically focused on keeping the player character inside the box.  You can as easily turn it on its head, and use the same principles to keep him out of the box.  For example, If you’re walking down corridor A and reach room 210, you next pass through a transfer point that takes you to corridor A outside room 280; if you reverse, the transfer will take you from 280 back to 210.  If the player doesn’t know the room numbers or layout, he won’t realize that he’s been moved—until he completes other sections of the map which go around this blocked area, and discovers that the distance between two points in the A corridor is an awful lot shorter than it should be.  You can make it so that access to that central area is only from a specific entry direction, such as above or below or a particular lesser-used corridor (but it can be exited at any point at which it connects).  Or you can determine a sequence of events or “switches” that must be activated to open the area to the characters, such as finding the key, or deactivating the grid, or realigning the circuits at every entrance.

I used an idea like this for a Minotaur’s labyrinth once.  My players were good; they could map a maze in a minute, comprehend any convoluted corridors I created.  The worst thing about facing a Minotaur isn’t the beast itself; it’s the fact that you’re on it’s turf, and it knows how to get everywhere while you’re wandering lost.  But once you’ve mapped a bit of it, it’s pretty easy to keep from getting lost, and the beast’s advantage is gone.  So what I did was create a layout of halls that frequently ran the same distance in the same direction, but parallel to each other a dozen feet apart. Then I put “transfer points” in the halls such that if you were going one direction you would get bounced to another hall, but if you were coming back nothing happened.  The creature knew its way around, and could use the magic to its own advantage; the players always knew which direction they were headed, but once they got involved in the tunnels they never knew quite where they were or how to get back.

Doctor Who faced a Minotaur-like beast called the Nimon once (I won’t swear to the spelling).  This time it was Tom Baker finding his way through the maze.  The thing that made that maze so difficult was that it constantly changed—he worked out that it was a huge set of switches in a communications and transmat system.  That’s a very difficult thing to do—but I can think of two good ways to make it work.  One would be to draw up maybe four or five distinct maps that were the same size and shape and had a few good fixed internal landmarks; that way at random intervals you could randomly change which map was in effect.  Of course, jumping from map to map could be tricky.  You might try making one map on paper that had the landmarks and a few fixed walls as reference points, and then getting four or five sheets of clear plastic overlay to put on top of the map, on which you would draw (or maybe if you’re really ambitious line with thin strips of black tape) the details of each position.  When the layout changed you would pop the new overlay on top, see where the characters are, and slide the old one out.

Of course, this idea doesn’t actually fit the pattern of the others, the pattern of moving the players from where they think they are to somewhere else.  But it probably makes them feel like it does, and sometimes that’s even better—especially if you’ve used tricks to move them around before.  They’ll leap to the conclusion that you’ve moved them, and begin trying to work out where they are.  You can get this effect with even simpler tricks.  Try making a matched pair of seemingly unique landmarks a short distance from each other in a confusing section of paths.  Players unaware that there are two (and especially those uncertain about their mapping skills) will come to the second and think they’re back at the first.

Something like that happened in one of my games, when the player was exploring the world we call Tristan’s Labyrinth.  (It was not called so when Tristan was exploring it.)  The labyrinth is endless; it is made of an L-shaped section designed to fit together such that all exposed sides are the same length (well, a single and double length) with doors that match up, so that you can build outward from one to as many as you need.  This means the same patterns of rooms appear, but not always in the same directions.  You can get the same effect with any of a number of random-connect dungeon floor plans; somewhere I’ve got a set of squares and rectangles published by TSR a generation ago, although I was never terribly happy with the way they fit together.  Just use the same piece against itself, turned around.  In the one game, the player found himself in a room with an interesting shape and several exits.  Deciding to use this as the base for his explorations, he traced out one of the exits some distance and back again, and then another.  The third tunnel took him off the map piece onto the adjacent piece, and connected to another tunnel which led to that same room on the next piece of map.  Carefully he followed it, reaching that identical room.  He looked at it.  He studied it carefully.  He compared it to what he had already drawn.

And then he changed his map.

If you use these tricks, there will be many times when your players will start erasing what they’ve charted, changing and fixing and trying to figure out where they are and how they got there.  But there is nothing like realizing you have gotten them so confused they are erasing the map when it was right.


Previous article:  Story-based Mapping.
Next article:  Doing Something.

Faith in Play #31: Magic Roads

This is Faith in Play #31:  Magic Roads, for June 2020.


Some years back I was playing in a game in which the city was ruled by chaotic gods who objected to anything being orderly or sensible.  This was particularly noticeable in connection with the roads:  it was impossible to make a map.  I secretly believed that this was because the referee didn’t want to make one himself and so thought it was easier just to pretend that he knew where everything was and how to get there, and make it up as needed.  In play, though, if you wanted to get somewhere in the city, you asked for directions from a non-player character who knew, and you followed them precisely.  These directions were as much ritual as geography–you might have to go around a block and find yourself on a different road when you returned to your starting point, or go halfway down a road or into a cul-de-sac and then return before continuing, or walk under an arch or between the columns on the front of a temple.  If you missed your turn, you hoped you could get back to wherever you began and try again.

I was reminded of this last night as I was driving home and came to the intersection pictured in that satelite view (courtesy Google Maps) pictured to the right.  Coming down route 109 from the west northwest (top left corner) you bear left when 109 curves right into Cape May (The Lobster House, one of the best seafood restaurants in the state, is right below the map) and come to a traffic light.  This is the onramp for exit zero on the Garden State Parkway, which runs off to the north northeast.  There is a conspicuous sign there that says No Turns, so you continue straight across the intersection onto that loop that goes around and returns you to the same traffic signal, where again you go straight to merge with traffic coming over the bridge on 109 from Cape May to get on the Parkway northbound, which begins here and goes off the top right corner of the map.

I’m sure that the intersection is designed that way because during the day, and particularly during the summer, traffic is crazy and someone trying to make a left turn would just hold everything up.  As I sat there around midnight on a late February night with no other cars in sight waiting for the light to change, an odd thought struck me.  It wasn’t that there would be no harm in simply making the left turn and cutting out the loop.  It was wondering about a road where if you made that left turn instead of taking the loop it would take you somewhere else.

I sometimes use my Global Positioning System to direct me to places I already know how to find.  I do it partly because I am interested in whether Google thinks there’s a better way to go than the way I know, but also partly because I know that the system is updated in real time for things like traffic jams and accidents, and have more than once had it send me by a different route than it usually does because the usually longer route will be quicker.

All of this comes to me now as illustrative of divine guidance and intervention.

Like most people, I am often annoyed when a traffic signal turns red as I am approaching.  I am annoyed enough that I often watch the pedestrian signals–at least here in New Jersey they’ve begun installing “Walk/Don’t Walk” signs with countdowns which turn to “Don’t Walk” when they reach zero and usually also change the green light to yellow at the same time, so I can estimate whether I’m going to make the light.  When I don’t, though, I sometimes remind myself that God might be stalling me to avoid a potential accident or incident ahead.  My father often said “Don’t be there when the accident happens,” and it may be that our Father takes these little steps to prevent such events–obviously not always, but sometimes.  There is somewhere a book of stories about people who called out of work or were delayed on the way to their offices in the World Trade Center on that fateful day in which so many died.

And so I wonder about our path through life, and whether God sometimes takes us to the place we always expected to go by the route that we never could have foreseen, because it was the best way to get us there.  It might even be that “straight down Main Street and make a right on Broad Street” won’t actually get you to number seven South Broad Street, because that address won’t be there unless you go a block down thirteenth and come back up fourteenth before continuing.  Like the home of Sirius Black, if you don’t take the right steps to get there the destination can’t be found.


Previous article:  Conflict.
Next article:  Zealots.

RPG-ology #30: Story-based Mapping

This is RPG-ology #30:  Story-based Mapping, for May 2020.


I have mentioned before that I belong to a role playing game mapping group on Facebook.  Every day people post beautiful world maps similar to the ones pictured here and ask for feedback.

I am not a cartographer; I am not an artist.  When aspiring young artists send their work to me for my opinion I send it to my art director, because my opinion isn’t worth the price of a cup of coffee on free coffee day.  If they want to know whether it’s beautiful, well, as I often say, a thing of beauty was made by someone else, and they look nice enough to me.  If they want to know if the maps make sense geologically and geographically, I can point out problems (such as those we’ve covered in previous RPG-ology articles including #5:  Country Roads, #10:  Labyrinths, #13:  Cities, and #18:  Waterways).

But if they want to know if the maps are useful, it always makes me feel like that’s not really a good question.  I can’t imagine ever having a use for them—but it took me a while to understand why.

Map by Steve Gaudreau

When I start a map, I begin with the question, Where are my characters right now?  Unless I have a good reason to think otherwise, that is the middle of the piece of paper that’s going to be my map.  (Even when I make maps on a computer I generally have a “virtual piece of paper”, boundaries of the image file and a graph paper grid covering most of it.)  This probably includes a vague notion of Where is the rest of the world?, but as Max Smart once said, “I’m not saying that the rest of the world isn’t lost, 99.”  I need a vague notion of how the characters got here which contains some information about the rest of the world, but since they’re not going to live that part in the story I don’t really need details.

What I do need is the answer to two essential questions.  The first is What is around them that they are going to want to examine?  If they are in a village, I need an inn, stables, tradesmen and craftsmen, probably a constabulary, homes of those who live in town, and probably at least one place of worship.  If it’s a city, I’ve given myself a lot more work, because there are a lot of places someone can go in a city.  In most cases I don’t really have to know how far it is from London to Paris, but I do need to know how far it is from the rooming house to the grocery store.

Map of Kaiden by Michael Tumey

The second question is Where are they likely to go from here?  Not Paris, we hope, or at least not yet.  The first place they’re likely to go is whatever place I have planned for them to have their first adventure.  That might be a dungeon, or a ruin, or an office building, or a spaceship, but whatever it is, I now have to expand my maps to show how to get from here to there, and what they will find when they get there.

There will be other places where they will go.  If they acquire valuable objects, whether jewelry or magic items or tapestries or computers, they probably need to take them somewhere to sell.  That means I need a place where people buy such things, and I need to map the road between here and there and treat that place much as the starting point, creating what they are likely to see when they arrive.  But I didn’t need any of that when the story started; I only needed to have a vague notion of where it was and what was there, so I could put the time into creating the map later.

I’ve called this Story-based Mapping because it is fundamentally about creating the world to meet the needs of the story.  I’ll give kudos to Seth Ben-Ezra’s Legends of Alyria for using this concept.  His world, Alyria, has a handful of significant landmarks—a major city, a huge library, that sort of thing.  When the game starts no one has given a thought to where they are, and there is no map.  When someone says they want to go to one of these places, the plot and the dice dictate how far it is, how difficult it will be to get there, and from that point forward we know where that particular landmark is relative to where we started.  In fact, we might have established where two such landmarks are relative to our starting point but not yet know where they are relative to each other—the plot may at some point dictate that they are adjacent to each other, or that they are miles apart in opposite directions, or that there is an impassible mountain range or waterway or chasm separating them.

This is why those huge world maps don’t interest me.  When I’m running a game or writing a story I need the map to form to what I’m writing.  If I already have a complete map of the world and suddenly I need a pirate base somewhere near my port city, I have to scour the map to find an appropriate location for such a base.  If I’m working with a story-based map, I simply have to expand the map to include the cove or island or port that provides my pirates with a safe haven, and it can be perfect for their needs and pretty much anywhere I want it to be that the characters have not already investigated.

I don’t think those huge maps are useless.  If you are creating a world for other people to use in their games, such as Krynn for the Dragonlance Adventures, having a map that shows where all the countries are located will help those other people run games in them.  But I think that something like the map of Middle Earth, while it might have been drawn from Tolkien’s mind before he started writing, arose organically from the story he wanted to tell:  I need hobbits to start in a quiet remote part of the world and travel a very long way through a lot of dangers but also a few safe spots and ultimately reach a distant dangerous place where they can destroy the Maguffin. Let’s outline what those dangerous and safe places are and where they are located, and then we can create the story to connect the dots.  So if I know what the entire story is before I start writing, I can create the entire map to fit it—but I never know the whole story, not when I’m writing it and certainly not when I’m “playing bass” for a bunch of players who are going to create the story.  I need to be able to create the world as the story needs it, not be locked into land masses and cities and waterways that were created in the hope that they would make a good place for a story.

I’ll probably be thrown out of the RPG Mapping group for this, but I hope it helps some of you understand how to approach making useful maps for your adventures.

Thanks to artist cartographers Steve Gaudreau of Map Alchemists and Michael Tumey for the use of their world maps.


Previous article:  Political Correction.
Next article:  Screen Wrap.

RPG-ology #18: Waterways

This is RPG-ology #18:  Waterways, for May 2019.


We mentioned rivers, lakes, and other bodies of water in connection with maps when we talked about Country Roads and again when we were talking about the placement of Cities, but we barely touched on them, more from the perspective of their influence on other aspects of our maps and our worlds.  Maps and worlds, though, are complicated things, in which everything influences everything, and understanding how waterways work will help us put together better maps.

This is difficult for me, because so much of it seems obvious to me so I expect it will be obvious to everyone else.  However, I have the advantage, as I think I mentioned in Shock, of over a thousand miles of long-haul canoeing, so I am perhaps intimately familiar with rivers and lakes and ponds and how they work.  I thus hope that I’m not telling you too many obvious points, and that some of this proves to be practical.  Let’s start with some terms.

A river is pretty much any waterway that flows downhill.  They can be big or small, swift or lazy, shallow or deep, straight or meandering, rocky or clear, in any combination.  Smaller rivers are often called brooks, streams, creeks, and similar diminutive titles, but the only significant difference is the attitude of the people toward the waterway and the probability of it going dry, which rivers rarely do.

Lakes and ponds are usually found as interruptions in rivers, and they are distinct from rivers in a significant way.  A lake or pond is formed in essence when water pours into a natural basin and has to rise to the level of an exit point.  Because of this, the surface of a lake or pond is level, while that of a river is always sloped–if you look at the accompanying photo, you can see that the downstream end is downhill.  In the vernacular, lakes and ponds are generally distinguished by their size, but technically they are distinguished by their depth:  a pond is shallow enough that water plants such as waterlilly pads can root on the bottom and grow on the surface, while a lake has at least some areas in which it is too deep for that.  Lakes and ponds are sometimes created intentionally by the use of dams, built by people or sometimes by animals, most typically beavers.

It is difficult to distinguish a sea from a lake in many cases.  Seas tend to be the terminus of rivers, at least one and often several, but most of them either drain into or are contiguous with the oceans, which are also sometimes called seas but which as a word tends to refer to the vast expanses of water separating the continents.  The two exceptions to the drainage rule are the Dead Sea, which is constantly evaporating and so is too salty to support marine life, and the Mediterranean, which also loses its water to evaporation but is large enough that its salinity, although elevated, is not inimical to such life, and fishing and the like are active there.  (It is easy looking at a map to suppose that the Mediterranean drains into the Atlantic Ocean through the Strait of Gibralter, but the water there is mostly flowing very rapidly in the opposite direction, salt water from the Atlantic constantly replenishing the losses in the Mediterranean through what some have called the world’s largest waterfall. There is an undercurrent flowing westward as a small amount of dense saltier water goes from the Mediterranean to the Atlantic, but the bulk of the volume is inflow from the Atlantic.)  It is also the case that seas tend to be salty while lakes tend to be fresh, but this is not a hard and fast rule, there being a number of salt lakes in the world.  Part of this is because the distinctions between lakes and seas are not made in all Indo-European languages, and English has often translated words strictly that were used loosely.

A passageway that connects two bodies of water of the same or similar level is usually called a strait (or sometimes straits), usually unlike a river because water flows in and out both ends generally with the shifting tides.  If it is wider or longer, it is often called a channel, but this word also refers to the best path through a river—rivers tend to carve a deeper groove through which most of the water travels, and boats and ships navigate through these deeper sections either with or against the current. In modern times, these channels are marked by buoys, red buoys to the right when traveling upstream (“Red Right Returning”), black buoys marking the other edge.

A bay frequently appears as a brackish (that is, salty but less salty than the ocean) body of water connecting a river to a sea or ocean.  As the tide rises, water from the ocean pours into the bay, often forcing its way upstream reversing the “normal” flow of the river; the Delaware River is brackish as far upstream as Trenton, New Jersey, about eighty miles upstream, about fifty feet above sea level, and this reverse flow is often used by ships to navigate to inland ports upriver.  As the tide ebbs the bay drains into the ocean, and the river into the bay, and fresh water makes its way downstream to wash away the salt.  Because of the backwash, those upstream ports have rising and ebbing tides, but these are out of phase with the coastal tides that drive them, often by as much as six or eight hours, depending on how far upriver you go.  A very small bay-like inlet is usually called a cove; a lagoon generally is a type of coastal pool that fills from ocean spill when the tide rises over its banks, and then slowly evaporates, frequently not completely before being refilled.

A wadi is something like a river, but significantly different.  Common to inland tropics such as Africa, the wadi is a watercourse that floods and dries in a seasonal cycle.  During the “rainy season” water falls in the highlands and flows down very like rivers, working downstream and gradually covering thousands of acres of ground, pooling but flowing, spreading over wide expanses of open space.  Animals are aware of the seasonal cues, and migrate toward the anticipated flood; plants desiccated from drought spring to life and blossom.  For a few months it is a lush wet marshy world, water plentiful, wildlife active.  Then gradually it all evaporates, leaving the dry grassland to wither in the heat, as the animals scatter to places better able to support them during the drought.  The water from a wadi never reaches the seas, soaking into the earth and evaporating into the air long before joining any other watercourse.  Wadis do not support ship traffic or permanent settlements, because the water level is non-existent for a significant part of the year and rarely deep enough for more than the smallest craft.

Swamps, marshes, bayous, and deltas all tend to be areas where a river spreads out to a shallow wide area, usually with a channel passing through it somewhere but often a confusing labyrinth of waterways leading to dead ends and shallow muck.  Wadis do support marshes and swamps during their wet periods; bayous and deltas tend to be at points where the river meets the sea, and are brackish like bays.

Now, this might sound obvious, but water falls from the sky.  Really all of it does.  Water in wells and water coming from springs is water that fell from the sky and soaked into the ground, then collected atop or between layers of rock and either sat waiting to be collected or built up pressure from gravity until it spurted through an exit.  It gets into the sky by evaporation, the vast majority of this from the vast expanses of tropical oceans—if your world does not have vast tropical oceans, you will have a lot less rain, and a lot less fresh water.  Evaporated water, water vapor, is held in greater quantity in denser warmer air; if the air cools or becomes depressurized, it cannot hold as much water and so releases it.  This is why so much precipitation (rain and snow) falls on mountains:  warm moist dense air currents are shifted upward into cooler low pressure altitudes, and can no longer hold as much water.  From there it collects in streams or soaks into the ground.

There is an interesting atmospheric phenomenon at this point.  As water falls, it washes carbons out of the air, turning into mild carbolic acid.  It has always done this; this is not a modern result of air pollution, although air pollution does contribute to it.  Carbolic acid which lands on dirt and soaks into it decays and releases its carbons back into the atmosphere.  That which lands on rock and flows into streams dissolves the rock, creating calcium carbonate which washes downstream into the oceans, burying the carbon for millenia.  That’s not really useful to this discussion, though, so ignore it.

Technically, a well is a hole dug deep enough to hit what is called the water table, the level under the ground where bedrock prevents water from seeping deeper, and so has water refilling it constantly from the surrounding lands.  It is sometimes confused with a cistern, which is a dry hole usually lined with stone designed to catch rain when there is rainfall and keep it deep and cool in the ground during the dry seasons.  The famed Jacob’s Well is actually a cistern.

This is also obvious:  water flows downhill.  Because of this it is constantly “seeking” the lowest point, and that means it collects into fewer larger rivers.  If it pours into a low point—call it a basin—it collects there, rising as a pond or lake until it rises over the lowest edge.  A lake can have several rivers feeding it, or no rivers feeding it if it is fed by a spring or springs below its water line, but rarely does it have more than one draining it—odds are good that there will be one lowest point, and once the water starts pouring through it erosion will make that point lower.  If the lake is filling faster than it is emptying, it might rise high enough to begin spilling from another point.  However, most typically these are near enough each other that the streams soon join creating an island at the head of the river.  If the two streams are headed in different directions, it is most commonly the case that one of the outlets will erode until all the water passes through it, the other becoming dry unless it is fed by other water sources below.

Where the ground is steeper, the water moves faster and generally straighter.  It follows the lowest ground, but in doing so carves the path deeper, sometimes wider, removing the dirt and softest stone.  If it comes into a pocket of harder stone, it will be turned, but the turning will create swirls and eddies which often drill deep spots in the riverbed.  The northern reaches of the Delaware River are frequently shallow enough to wade through, but where it turns sharply at Narrowsburg, New York, there are whirlpools during flooding and the depth at the curve is over a hundred feet deep.  Rocky rapids form where the ground is too hard to erode easily and the slope is steeper, as the river becomes forced into a narrow space often between high banks and spreads over the area to become swift and shallow, the irregular bottom redirecting the current in directions difficult to predict without surveying in advance.

Where the ground is less sloped, the water spreads to cover a wide path and flows more slowly, but still tends to follow the lowest ground and carve a channel.  In older sections of the river these channels are often meandering, and as the water ultimately settles into them they form snake-like slow rivers with very little noticeable current, frequently surrounded by marshy ground, meadows, and flood plains.

As rivers join, they become wider and deeper, and usually become straighter as the land is less able to resist the flow of the water.  These wider deeper rivers which ultimately reach the sea are frequently navigable by ocean-going vessels, and as we noted are also subject to reverse flow when the tides rise, thus brackish but also easier to navigate upstream.  They will carve deep sections particularly at curves and bends in the river, as in Narrowsburg, creating good ports at such curves, considerably more so than along straight paths.  Upstream of a certain point ocean vessels, which have deep drafts to provide stability in rough seas, give way to shallow-draft river boats, able to navigate farther upstream.

The same currents that form harbors on rivers do so where rivers hit the seas, which makes such points doubly convenient for trade, as a port there accesses both the oceans and the river.  Such harbors are also created where the coastline recedes sharply, as ocean currents form eddies which create depths near the shoreline, although if the surrounding ground is low there will probably be a river outlet there, and if not the deep water is likely to be surrounded by cliffs, making for good anchorage but a bad place for a port.

So to summarize, most rivers begin from streams in mountains, flowing downhill and collecting into larger rivers, forming lakes in low spots, rapids over steep rocky ground, meandering courses over flatter softer ground, ultimately becoming large enough to support riverboat trade and then ocean vessels, subject at the downstream end to tidal backflow, emptying into seas and oceans sometimes through intervening bays.  Harbors form where currents have carved significant depths, usually at the mouths of the rivers and at river bends.

Now you have some idea of how to put the waterways on your maps.

I have omitted canals from this discussion.  Men build canals usually where there are two disconnected waterway systems near enough to each other that it would be commercially profitable to be able to run boats or ships between them.  Usually these involve mechanical locks which enable the control of the flow of water between the two systems, particularly if they are not at the same level, and typically because such canals often have to cross ground that is higher than either of the waterways (the reason the waterways haven’t flowed into each other).  Sometimes canals are built to get around sections of a river that are not navigable, if there are navigable sections upstream of falls or rapids.  They are a lot of work to build, operate, and maintain, and if neglected gradually deteriorate.


Previous article:  With the Odds.
Next article:  Treasure Auction.

RPG-ology #10: Labyrinths

This is RPG-ology #10:  Labyrinths, for September 2018.


In game terms, a labyrinth is a geometric puzzle, a system of passable and impassible spaces solved by the discovery of a consecutive path of passable spaces connecting some number of points, commonly the entrance and the exit.  A maze, usually, refers to a type of labyrinth for which there is a unique solution, only one path that connects two points; a labyrinth might instead have many solutions, or no solution.  The distinction is significant in several ways; they are related puzzles, but both the ways in which they are created and the techniques for solving them are different.

Engraved and designed by Toni Pecoraro 2007. http://www.tonipecoraro.it/labyrinth28.html CC BY 3.0

Labyrinths can occur naturally, when geologic forces crack rocks in seemingly random patterns.  Even mazes can be naturally occurring—if a tunnel system was carved by water which has since mostly evaporated or drained away, it commonly carves one exit point, and then the current follows that path and ignores the others.  Mazes are more commonly created by intelligent action, although sometimes an intelligence will create a labyrinth for any of several reasons.

Labyrinthine road patterns sometimes develop from the process of acretion, as new residents add new housing and thus new streets attached to old ones.  Suburban developments are often labyrinthine by design so that residents familiar with the roads can exit in any of several directions but others will not consider the connected roads a viable short cut between two points outside the development.

The Minotaur was kept in a labyrinth because a maze would have been too easy to solve.

A maze in two dimensions is easier to solve from above than from within; the eye can trace patterns and look for the connecting path, spotting and avoiding dead ends early.  Still, from within a two-dimensional maze you are guaranteed to find the way through if you pick one wall and follow it.  This will take you into many dead ends, but it will take you out ultimately.  A labyrinth with more than one solution cannot necessarily be solved this way, as there is a high probability that you will be caught in a loop.

Three-dimensional mazes are considerably more difficult to solve, because we are not generally accustomed to considering them three-dimensionally.  These are most easily created as multi-level constructions with stairways, ramps, or chutes and ladders connecting them in specific points, often connecting some levels but not accessing intervening levels.

Five level three-dimensional maze, top level to the left, crossbars mark ladders, with markers for up and down. Entrances are on the middle level, center of left and right sides.

One mistake often made in maze design is designing inward only—that is, many mazes are easily solved by working backwards, the tricks and turns and deceptive paths all designed to mislead the one coming in from the front.  This is not as much of a problem in a role playing game maze, because these can often be placed in locations in which the characters will initially approach them from one side.  On the other hand, the designer can take advantage of this by creating the maze backwards, such that characters will easily find their way in but will be confronted by the confusion on the way out.  However, many tabletop gamers become very good at mapping, so the scenario designer might need some particularly complicated tricks to stymie his players.

Fortunately, fantasy and science fiction give us such tricks.  In Dr. Who:  The Horns of Nimon, the space in which the Nimon lived was a giant logic circuit, the walls switches which seemingly randomly switched from “A” to “B” positions making it impossible to have an accurate map created from passing through it.  I have recommended using teleport points, in either fantasy or science fiction settings, by which any character crossing a specific spot on the map in a specific direction is moved to a specific other spot on the map not necessarily facing the same direction, but is not moved back on the return journey, passing the arrival point unaware that it was there.  There are many ways to use this—creating recursive occlusion, as in Dr. Who:  Castrovalva, a section of the map in which there are many entries, but only one exit, all the other exits delivering you to the entry point on the opposite side of the isolated area; creating maze-like labyrinths in which the characters are moved to parallel paths but the occupants know how to use their teleport points to get where they want to be; creating duplicate rooms in which characters who enter one room always leave from the other.  I have used all of these techniques, and have had players trying to resolve their situation for several play sessions.

I have also confused players by using maps with repeating patterns, causing them to believe they had returned to a place they had already been when they were instead in a different place exactly like it.  Nothing is quite the same as watching a player attempt to erase and correct a map that was already right.


Previous article:  Three Doors.
Next article:  Scared.