Battle for Wesnoth Campaign Design How-To

If you've never written a Wesnoth campaign, designing a good one is likely to seem like an intractable problem — too many different input variables feeding back into each other with no way to know that something you tweak at a late stage in the process won't invalidate assumptions you made earlier, and an ill-defined payoff function.

In fact, there is a way to structure the process into serial stages such that you will seldom have to go backwards after you've finished a stage, and will usually only have to handle one optimization problems at a time. Here they are:

Do your storyline for the entire campaign first. The later stages can be done in series for the entire campaign, or by looping through them for each scenario in succession. Occasionally balance tuning will require you to tweak a map; otherwise they separate pretty cleanly.

By applying the advice in this how-to, I was able to design and code 12 of the 13 scenarios in The Hammer Of Thursagan in about fourteen man-days spread over five weeks, including balance tuning. (The last scenario was farmed out to a guest designer who is famously good at the particular style of scenario I was after.) A more experienced designer could probably apply them more quickly.

First, write your storyline. Battles may be the center of Battle For Wesnoth, but writing an interesting storyline and designing battles to fit works better than designing battles and then wrapping a story around them.

So, start by writing a storyboard for your entire campaign. You should do this all at once rather than putting off the late bits until you've written WML for the earlier ones. Otherwise your storyline is likely to develop awkward joints rather than flowing smoothly.

The storyboard should contain a section for each scenario, beginning with its title and continuing with the story text and dialogue. The storyboard should also include a description of the map and the kind of battle you want to have. It should describe any special events in the scenario, how they may fire, and what the effects are.

Here is an example of a storyboard section from The Hammer Of Thursagan. Most storyboard sections are shorter than this; I chose a complex one to give an idea of the range of things you may want to do in a storyboard.

The WML for THoT::High Pass doesn't exactly match this; I added ogres and wolves as possible enemies, and some of the dialogue has changed a little. Your storyboard should be a support, not a straightjacket; its function is to help you focus on storyline composition without being distracted by WML and implementation details.

You don't even necessarily have to write out every single line of dialog in your storyboard drafts. I like to do that, but a placeholder like “The captain and the mage discuss how difficult the upcoming battle will be” is probably good enough for a first pass.

One last note about storyboarding: pick a reasonable campaign length (count of non-talk-only scenarios) and stick with it. We've found by experience that 10-12 is a good medium length, 16-18 is long, and over that is epic and nearly unmanageable. It's difficult to sustain interest over 16 scenarios. If you find yourself plotting a 25-scenario storyboard, beware lest your stamina fail to match your ambition.

Thursagan's Hammer is 13 scenarios; of those, scenarios 2 and 13 are talk only, I chose that length carefully after having studied the mainline WML and noticing that 11 “real” battle scenarios seems to be a sweet spot (a point, by the way, on which the original designer of Wesnoth says he strongly agrees). You should choose yours just as carefully.

A good storyline is not just a series of incidents hanging in the void. A good storyline has continuity within itself and connections to the rest of the world of Battle For Wesnoth.

Use place names. “Behold, the High Pass…we are halfway to Kal Kartha.” You create a sense with these that the story is situated; the landscape means something to the characters, and the reader is invited into their world of meanings. It's even better when you can use a place name on the main Wesnoth map; this ties the campaign to the known world.

Use calendar references that situate the campaign in the Wesnoth timeline. The intro for the first scenario of THoT ends like this:

This is a story hook. We know where it happens, we know when, and we've introduced our first character: the (not yet named) captain of the East Gate of Knalga. The first speaking lines in the scenario will be his.

Use foreshadowing and back references to create continuity. In our storyboard for High Pass: “There is a school of mages near the east end of the pass.” This is a really simple form of foreshadowing; the player is quite likely to think “School of mages? Cool! I hope I get to see it in next scenario.” We give the player something to anticipate — and when he does actually see that school in Mages And Drakes (#7), we've created a continuity, a bit of thread that ties High Pass together with Mages And Drakes.

“Something frightened those orcs enough to make them push west into Alliance territory” — that's a back reference to the action of Invaders (#5). By writing this, we give that scenario a meaning it didn't have before; we tie it to the present of the characters in High Pass. This is another kind of continuity, making the story stronger.

Develop characters. Look at this again:

We get a good sense of what Ratheln is like from this — gruff, sarcastic, and the kind of tough that will tear into a gryphon carcass with his teeth if he has to. Not a guy to be idly messed with. Players will remember this bit; the whole campaign just got a little more interesting.

Don't go overboard with character development. A lot of writers have been taught to believe that stories stand or fall on the quality of their characterization. This ain't necessarily so even in general, and in the very tight constraints of Battle For Wesnoth storylines believing it can all too easily lead you into overwriting.

Even a hundred words of dialogue is pretty talky in a Battle For Wesnoth scenario, and you have to budget a lot of that for plot. You can't afford to spend lots of verbiage on characterization, which means every bit you do has to count.

The basic trajectory of a Wesnoth campaign should work like the basic trajectory of any story — a building-up of tension, followed by a climax, followed by a wrap-up or resolution (writers call this the “story arc”). So simply for narrative reasons, early scenarios should be easy and later ones progressively more difficult. In Wesnoth, of course, this is also necessary because each scenario has to be matched to the rough number of veterans you expect your player to have when it starts.

In Wesnoth, an explicit resolution often takes the form of a single talk-only Epilogue scenario. From a strictly gaming point of view there's no point to an Epilogue because there's no battle; it's very much there to finish the story.

Long campaigns may actually have two or even three story arcs in sequence, all fitting into a single over-arc in which earlier sub-stories build up tension for the final resolution. Each such arc should finish we the achievement of some kind of marked goal, and give the player a sense of relaxation and accomplishment.

For example, in The Rise of Wesnoth (a very well-written campaign that repays careful study) there are three story arcs. One finishes with Haldric's departure from the Green Isle, the second finishes when Haldric sits down to negotiate with the elves of the Great Continent, and the third one climaxes with the final battle against the lich-lord Jevyan.

Another important rhythm is this: as you build up tension, alternate easy with hard scenarios. This makes good story — Tolkien relied on it heavily in plotting Lord of the Rings — but there is a specific technical reason to do it in Wesnoth: gold control. We'll talk about this more when we describe balancing techniques.

When you write your storyboard, it's a good idea to note which scenarios open, climax, and (if applicable) resolve each story arc, Also, note which scenarios are intended to be easy and which hard. That way you'll notice when you have two hard or two easy scenarios adjacent and get a good clue about something that might need fixing.

Now I'm going to talk about prose and style. I'm aware that unless you're already a fairly good writer, the advice I'm about to give will be about the most difficult part of this how-to to apply. But even if you don't consider yourself a good writer, read it and let it sink in; you may well surprise yourself later.

Battle For Wesnoth is a fantasy game. Your storyline will work best (be most accessible to the player, have the most interesting atmosphere) if your player finds your prose similar to the experience of reading a well-written modern fantasy novel of the epic or high-fantasy type — that is, not urban fantasy or horror, but part of the tradition largely derived from J.R.R. Tolkien and a few other lesser-known writers (James Branch Cabell, Lord Dunsany, E.R. Eddison, etc.).

Therefore, you need to know about the conventions for how high-fantasy prose should sound. If you are an extremely good writer (like, say, the author of The Rise of Wesnoth), you can play directly against these conventions. Very few people are that good; the rest of us (including me) are better off following them as carefully as we can.

First rule: Crib shamelessly. Remember that when writing for Wesnoth, you are not trying for a literature prize. Lifting ideas and imagery from Tolkien and other great fantasy authors is just fine, usually much more appropriate than trying to pull the player into a private artistic world of your own.

Here's an example. I wrote the description of Mal-Ravanal's death at the beginning of the Epilogue to Eastern Invasion. Here it is:

I lifted the central image quite consciously from J.R.R. Tolkien's description of the passing of Sauron in The Return of the King:

Remember, some cliches are cliches because they work. Go and do likewise whenever appropriate. Don't lift word-for-word, though; that can lead to copyright problems.

Second rule: Fantasy characters don't use modern slang or speech rhythm. You should write in careful, formal English. If it's possible for you, imitate the longer sentences and more rounded, relaxed rhythms of late 19th- and early 20th-century English as written by an Oxford don (this was Tolkien's dialect).

Third rule: Use archaic and poetic forms — carefully. For example, “I fear that…” is better than “I'm afraid that…” I have Ratheln saying “Hail” rather than “Hello” for a reason; it creates a sense of some strangeness appropriate for a fantasy milieu.

Sparing use of poetic and dialect words is good. For example, in one of the THoT scenarios there's a line like this:

Many of your readers won't know that “muckle” is a Scots-dialect (and archaic English) word meaning “a large amount” or “great”. But a few will, and a few more will guess the meaning correctly. For those who don't, the presence of a word they don't know will be a bracing little hint of the strange — as long as (and this is important!) the sentence remains comprehensible without it.

Don't go overboard, though. Going all Shakespearian with prithees and sirrahs and thou arts isn't necessary and would just distract your players. Use your archaisms like spices in cooking; to add flavor, not to overwhelm.

That last example sentence illustrates a related tool: Yon dwarf has an accent. In this case, specifically, a Scots one. I've made a point of giving some of the dwarves in the campaigns I write or adapt that accent. The degree varies: Lord Hamel (in Northern Rebirth and The Hammer of Thursagan) has a heavy accent, Aiglondur a light-to-nonexistent one. But it differentiates them from humans in a useful and interesting way.

(For non-English speakers: In English-language folklore, the Scottish share many characteristics with fantasy dwarves. Both are tough, dour, canny mountain folk who are good at engineering and hold grudges forever; the similarity even makes sense to a Scot. This is why a Scots accent “feels right” for a dwarf. In the Lord of the Rings movies Peter Jackson gave Gimli a Scottish accent, with reason.)

If you have the skill for it, give your characters accents — or, at least, distinguishable speech patterns. Elves should sound flowery and hyper-correct, dwarves should sound dour and tough, orcs should sound brutal and angry, trolls and ogres should sound stupid.

Fourth rule: Change register appropriately. All the tricks I've been talking about (cribbing from authors, formal English, poetic and dialect words, accents) become more appropriate and more important in climax scenes than they are in ordinary narration. At times of great intensity, shift your prose a bit away from colloquial modern English — make it more formal, more archaic, more fantasy-tinged, more powerful.

The most useful thing you can know about designing maps is that it seems to be actively difficult to design a map that both has visually interesting terrain and produces a boring battle. The AIs are quite senstive to movement costs; thus, they tend to seize on even small irregularities in your map and amplify them into relatively dramatic effects on how AI-controlled units move and attack.

Therefore, when you're designing a first-draft map you can generally relax and make interesting-looking doodles that fit your storyline, without worrying too much about shaping the battle. After you've played your scenario through a few times and seen what the AIs do with the terrain, you may find you want to tweak a few things, but I find this is often unnecessary. When I do tweak, more often than not it's just to adjust the density and placement of villages.

There is one specific gotcha about dungeon maps: it is not generally a good idea to draw corridors or openings only a single hex wide. These too easily become bottlenecks where cooperating weak units can hold up strong ones indefinitely, especially if there's a village nearby for wounded defenders to rotate through. It's frustrating to be on the wrong end of this, so don't draw such narrow apertures unless you have a specific reason for wanting a bottleneck.

We've mostly reduced the problem of designing interesting map to making visually interesting terrain. So, what makes visually interesting terrain?

The answer is this: real landscapes look like like fractal noise — 2-dimensional waveforms that are self-similar at all scales (treelike, cloudlike, wavelike). Human brains respond to this; in fact, we've evolved to like it so much that we generate artificial 1-dimensional fractal noise for pleasure, and call it “music”.

So, learn how to doodle fractal noise in the map editor and you'll have the trick of making maps that are interesting. That will translate fairly directly into interesting battles. I find that it helps to scribble quickly and roughly and turn your mouse errors into seeds for more fractal irregularities.

Calibrate the size of your map according to the speed of player units; a small map is one that takes 6 or fewer turns to move across in either the horizontal or vertical direction, medium-size tops out at 10, and anything bigger should be considered large. It's a common error to make too many maps too large.

Slogging troops across a large map is exhausting, especially if you have to do it a couple of scenarios in succession; thus, save the big maps for the handful of set-piece battles that wind up the campaign or a major story arc within it.

Map size controls the overall feel of a scenario; medium and large maps make for army battles, small ones produce an experience more like a role-playing game.

Heir To The Throne, the prototypical Wesnoth campaign, has exactly two large maps in 25 scenarios; of the remainder 18 are medium and 8 small. The Hammer of Thursagan has no large maps in it all; about two thirds of its maps are medium and a third are small. These proportions are typical for mainline content.

When you do need a large map for storyline reasons, give extra consideration to the possibility of using fog or shroud. With these features, the player's view is restricted. The element of discovery and surprise will make play more interesting.

Another technique that is especially important on large maps is special events and objectives. Give the player something besides a slog over lots of terrain to look forward to.

A larger map increases the expected number of units that will advance. If the scenario only provides a few unit types, and those have only single paths of advancement, the player will end up with a lot of almost identical units; this won't help with keeping things interesting. To counter this, invent storyline reasons to enrich the player's recruit list.

Use the storyline to help you design the map, then let the map shape the battle. This may sound too simple, but it really works.

The techniques I previously described for making large maps more interesting can make any scenario more interesting.

Variety of units and advancements is an especially good thing to maximize everywhere, not just on large maps. The more different unit types a side has, the more tactical options they will imply, and lots of tactical options make for interesting play. Large recruit lists make for interesting enemies, too.

Also, unusual combinations of units — and unusual oppositions of units — make for interesting scenarios. One of the most useful things to think about in roughing out your storyline is this kind of variety.

For example, in The Hammer Of Thursagan, there is one scenario that I designed specifically so the player would have the unusual experience of playing orcs and dwarves on the same side. Another was designed specifically as a mages-vs.-dragons matchup because that was a combination I thought players would never have seen before.

Scenario objectives other than the basic “kill all enemy leaders” are another good way to add variety. As a rule of thumb, try to come up with a special objective for at least one in approximately every three or four scenarios.

Here are some possible special objectives that have been used in various Wesnoth campaigns. Re-use these or invent your own.

Bear in mind that you can combine objectives, too, requiring a player to (say) both kill all enemies and meet a special condition.

Human beings like stories with vivid characters in them. One way to make a scenario or an entire campaign more interesting is to have the player encounter non-player characters (NPCs) that will travel with them.

I've already mentioned Ratheln from The Hammer of Thursagan; a more interesting example is from Northern Rebirth, in which a rescued prisoner may become either friendly or hostile depending on whether a previously-encountered NPC is still alive and with you when you rescue her. On the friendly branch, she later co-leads in a romance subplot. Northern Rebirth is at an extreme in having fully 11 potential NPCs in it, but every good campaign can have one or two of these and probably should.

NPCs have some unobvious benefits aside from enriching the storyline. One is allowing you to give the player special abilities in increase tactical options in a controlled way. The commonest version of this move involves introducing a friendly NPC mage or healer to a player side which cannot normally recruit such units.

In The Hammer of Thursagan, I invented the Loremaster unit line partly so that Angarthing's unusual combination of abilities (mobility, superior leadership, slow) would make the battles a bit more fluid and interesting; I felt this was especially important because dwarves have low mobility and relatively few unit types. Angarthing's abilities (especially superior leadership) would destroy campaign balance if the player could recruit lots of units with them. But having them manifest in just one NPC makes them manageable.

Another useful function of NPCs is to lead allied factions. Once again Northern Rebirth sets an example; in the final huge showdown battle no fewer than three of the NPCs walk onstage leading armies of their own.

It needs to be said up front: don't let your campaign degenerate into an exercise in piling up artifacts! Chase-the-shiny-thing sounds like fun but done too often it makes for boring gameplay.

Used sparingly, though, artifacts can add interest to a campaign. As with NPCs, they give you a way to introduce special abilities and tactical options in a controlled way. Probably the commonest variety is the ankh or holy water that makes a unit more effective against undead. The second most common is a weapon with a special attack, such as a flaming sword.

You can make an artifact more interesting in one or both of two ways. The first is to tie it into your storyline in some strong way. For example, in Heir To The Throne, possession of the Sceptre of Fire is an essential element of Konrad's claim to the throne. The second way is to give it some ability that the player is not likely to have seen before.

I took the second approach in The Hammer of Thursagan. The Staff of Righteous Flame confers a final-strike ability that is not hugely useful in a strict tactical sense and not tied to storyline, but remains interesting precisely because it's unusual.

But the real reason the Staff exists is that when I drew the map for Forbidden Forest (#10) I noticed that the village on the island in the lake at the middle of the map looked like it ought to be special in some way. Don't ignore impulses like this; they are your creativity trying to tell you something! So I turned the village into a temple and dreamed up the Staff to make it worthwhile to go there.

This solved two problems at once; it gave my campaign one unique artifact, and it made the most visually prominent feature of that map correspond to something real. These are both good heuristics to follow in your own designs.

The key fact that makes army balancing possible is this: no matter what faction you're playing, one gold piece is going to get you about the same sum of combat power and endurance. Units that have advantages in one direction (such as, say, the saurian combination of mobility and skirmisher ability) will have disadvantages in another direction (Saurians have relativity low hit points, so they die quickly in a standup fight at 1-1 odds).

Therefore, the Equal-Cost-Equal-Power Rule (ECEPR): you can balance armies fairly effectively by giving them the same amount of gold to recruit with. The Wesnoth maintainers tune units and factions with the main goal of ensuring that ECEPR stays true.

There are some important caveats to this. First caveat: some combinations of factions are more “unstable” than others — that is, while the expected outcome of 1000 fights between equal-cost armies from factions A and B is about a 50% split no matter which factions A and B are, some combinations are more prone to swing large around the mean. Thus they will seem very sensitive to tactics and dumb luck.

Dwarves or outlaws vs. orcs, for example, is pretty stable — unless the orcs have assassins, in which case the variance goes up (poison is destabilizing in general). Mages vs. undead is unstable; in general, pure archers vs. pure infantry is unstable.

Second caveat: to get that 50/50 split it has to be the case that each side is using the right countertactics against the other. Your chances running (say) an equal-cost army of dwarves againt saurians may be 50/50 in the large, but if you don't pull your dwarves into tight-packed groups to shield the wounded you're not going to get your standup fight at 1-1 odds; you'll find that saurian skirmisher ability will shift the odds dramatically against you. High mobility is destabilizing in general.

Third caveat: Fortifications. Units in castles or on terrain that favors their defense collect an advantage. An assault on a fortified position will require more gold to the attacking side to make it even. There's no real rule of thumb here: you have to balance-test and watch what happens.

Fourth caveat: ECEPR doesn't count player veterans in campaigns. Player veterans have a fixed cost of 20 each, which is less — often a lot less — than the unit cost if you had to buy it direct (assuming you were able to). An Archmage, for example, costs 59 gold and has about three times the combat power of a typical L1 unit; getting it for 20 gold is a steal.

Here there is a rule of thumb. L2 units tend to be just about twice as powerful as L1s, and L3 units roughly three times as powerful. Thus, you can multiply a player side's starting gold by the average level of its recruiting list to get a number roughly comparable to an AI side's starting gold.

To tilt a fight against one side, change the armies' starting gold. The unit to think about when you do this is a recruit-equivalent. A recruit-equivalent (RE) is the amount of gold required for each army to recruit an average L1 unit of its faction. So, for example, dwarves usually have a L1 Fighter costing 16 gold, a L1 Thunderer costing 17 gold, and a L1 Guardsman costing 19 gold; a dwarven RE is thus 17.33. Think in multiples of a side's RE when changing its gold level.

Here is a table of REs for some common recruiting lists to help you get the idea. The “Steps” column gives the total gold required for 6 REs (one castlefull) to 12 REs (two castlesfull).

Overall, L1 unit costs average 16; you can use that (and the steps 104,122,139,156,174,197,208) as a rough-and-ready guide when computing an exact RE seems like too much work.

One final wrinkle about RE: as a campaign progresses, an increasing fraction of the player's unit buys will be recalled veterans at 20 each rather than L1 recruits. So while you want to keep using REs computed by averaging recruitment costs for the AI sides, figure the player's RE will start to nudge 20 after three or four scenarios.

How hard is too hard? Remember that as a campaign designer, your job is to produce fun, not frustration.

Hence, the First-Time-Possible Rule (FTPR): It should be possible for a skilled enough Wesnoth player to win each scenario without any restarts first time he/she plays it, provided he/she doesn't make any actual mistakes and is not seriously unlucky.

Because your player accumulates veterans, first-time-win without restarts can still be just possible in a campaign's late scenarios even though they involve much nastier opponents than earlier on.

We have a distinction between Novice, Intermediate, and Expert campaigns; this is what defines “skilled enough”. At Beginner level, “skilled enough” means little more than “able to able to move and fight units in rough groups and rotate your wounded out of the way”. At Expert level, “skilled enough” implies tactical expertise — the ability to organize a flanking assault, ZOC-pin enemy units with mobile troops, manage a fighting retreat, etc. Intermediate is in between.

This is at the campaign or scenario's Normal level of difficulty; it is OK, and expected, that Easy will be easier and Hard will be harder. How much is up to you. A good way to go is to balance-test extensively at Normal level, then adjust gold and/or turns and/or recruit lists to make Easy about 25% easier and Hard about 25% harder.

The balancing method that seems to work for me is simply to play through the campaign often enough to get a feel for the number of veterans the player will typically have going into each scenario, and then tune the enemy gold so the player can just about beat it reliably at Normal level with those veterans.

You can find other good advice on scenario balancing at the Wesnoth wiki page BuildingScenariosBalancing

There's a problem in the Wesnoth reward system. Making too little gold in a scenario increases the chance that you'll fare badly in the next one, because you can't afford to recall enough vets to beat the turn limit. Conversely, success is self-reinforcing; beating a scenario early may mean you can use the bonus gold to beat the next one even more aggressively.

Without careful management, this can lead to a kind of feast-or-famine instability in which players of a campaign are either perpetually starved for gold and struggling in an un-fun way, or rolling in gold and able to recruit with such abandon that even hard scenarios are too easy.

This feast-or-famine instability is the main reason very long campaigns tend not to work. The exceptions that do work tend to have periodic “gold-eater” scenarios that are basically designed to drain the player's reserves. They then get reset to some reasonable minimum by the starting gold of the next scenario.

Son of the Black-Eye is a long campaign at 19 scenarios. Scenario #10 (Saving Inarix) is a gold-eater. You must recruit heavily (and expensively) to survive, and most of those units are going to die. Without this bottleneck, there would be far too much gold sloshing around in scenarios #11-#19.

Sometimes the opposite tactic is useful. The first really large fight in THoT is #5, Invaders. After several playthroughs I noticed that playing from campaign start to the end of #4 (Troll Bridge) seemed to involve about the right level of challenge, but that retaining enough gold to make Invaders winnable seemed unreasonably difficult. Rather than retune the earlier scenarios, I put a pile of treasure under the boss troll.

But the most reliable way to manage gold is to alternate hard and easy scenarios. The easy ones generate gold, the hard ones eat it.

You have two options about the method of gold carryover; picking the right one can make a large difference.

The older way, used in Wesnoth 1.4 and earlier, is to start each scenario with 80% of the finishing gold from the previous scenario or the scenario's minimum starting gold, whichever is higher. The new way, used by most campaigns in Wesnoth 1.6 and later, is to have 40% of the finishing gold of the previous scenario be added on top of the next scenario's minimum starting gold.

The new way results in less severe differences in the range of possible starting gold, and also rewards the player for all of his finishing gold even if he ends the scenario with with less than the minimum starting gold of the next one. It is also possible to use an arbitrary carryover percentage, but in mainline campaigns 40% is almost exclusively used.

Using the old way, if the minimum starting gold of scenario 2 was 100, the player would get no benefit from any gold he manages to accumulate unless it's higher than 125. This makes it much harder for players who are struggling with gold to climb out of their situation, because in order to get even a small gold bonus for the next scenario they must end the current one with such a large amount. Using the new way with 40% carryover, however, the player can finish scenario 1 with 125 finishing gold and receive a non-negligible 50 gold bonus for the next scenario, starting it with 150 in total.

It's probably a good idea to use the new way in most cases. It both rewards the player for even low finishing gold and provides slightly diminishing returns for higher finishing gold, so that the overall range of gold the players are likely to have is tightened somewhat.

Also, remember to tell the player how the carryover works in the objectives dialog! All mainline campaigns using the new way do this along with notes on whether there's an early finish bonus or not. Forcing the player to guess only places an unnecessary burden of uncertainty on them.

One major main thing to avoid in designing scenarios is landmines — random or unforeseeable events that make it impossible to win even if the player is playing intelligently. A fair number of user-made campaigns have been consigned to the outer darkness forever because they have nasty surprise moveto traps that are, in effect, landmines.

This is not to say that all moveto traps are bad. An important feature of good ones is that the story dialog gives clues that are sufficient to avoid them, or mitigate their effects, if you're playing smart. Remember, your goal is to challenge and stimulate the player, not randomly frustrate him/her.

Another thing not to do is the “tomato surprise” — an unavoidable event that, once you know about it after the first playthrough, completely changes the way you will play the scenario (even how you will play it before the event fires) on the second and later plays.

Before 1.6, the Under The Burning Suns scenario A Stirring in the Night (#2) had a tomato surprise when the player-side hero Garak turned undead and the objective shifted to defeating him; this was a significant flaw in an otherwise interesting and well-written campaign.

Beware of giving your player an AI ally as a balancing tactic. It's quite hard to set up a battle in which the AI ally is reliably helpful. Ally AIs are prone to quirks like grabbing villages when they ought to be fighting, or running units off into the middle of nowhere for no obvious reason. It's unwise to count on them to do more than blunder into the enemy's path and slow him down a bit.

If you want the ally side to be really helpful, consider giving the player actual control of it. Northern Rebirth uses this technique in a couple of scenarios, including the big final one (Showdown, #13). The player gets to run both the human and drake sides, with elves and dwarves as AI allies.

When regulating the difficulty of a scenario you have three main knobs you can turn: the starting gold, the recruitment lists, and the turn limit. When you want to turn the difficulty up, increasing enemy gold is probably the first thing you should think of and shortening the turn limit the last.

Why? Because few things are more frustrating than to have the last enemy boss cornered, beat his hitpoints down into the red zone…and then, just as your valiant warriors are about to deal the death stroke, lose because you ran out of time. Players hate this, and with reason. You shouldn't do it to them.

Tight time limits occasionally have their uses. One is in “get your hero to the signpost” scenarios, like the first one in Heir To The Throne, or THoT::High Pass. Another is the inverse; scenarios where you have to hold out against enemies until the bell tolls, like the first scenario of Eastern Invasion. In both those situations you can use the time limit to build dramatic tension, and it seems natural in those contexts.

But for straight battle scenarios, time limits are almost always the wrong way to control difficulty. Think of them instead mainly as a way to control the amount of gold carried forward into the next scenario.

A good alternative to a short time limit is to give the enemy lots of income. That way, if the player doesn't defeat him quickly, he will pile up enough gold for a crushing advantage.

Sometimes a campaign will have a plot that makes it unreasonable, in storyline terms, for the protagonist to have the same veterans' list throughout the campaign. This is especially likely if it's a major plot element is that the protagonist is isolated and far from home: Gweddry in Eastern_Invasion, for example. (The extreme case of this would be Delfador's journey through the Land of the Dead in Delfador's_Memoirs.)

You should, however, keep this sort of thing to a minimum. Players love building armies. They'll put a lot of effort into leveling up their followers. If you vanish their recall list without good reason and fair warning, they are likely to feel cheated.

It's perfectly possible to write an interesting campaign with a linear plot and the final objectives always shown at the beginning of each scenario. Eight of the twelve campaigns currently in mainline fit this description.

For the more ambitious, there are a couple of techniques you can use to create more possible ways to play through the campaign and set up interesting surprises. But these techniques have to be handled with care.

One technique is branching. It's possible to set up logic that will dispatch a player to one of two (or even more) alternative next scenarios. Typically you do this through a menu choice presented on victory.

In The South Guard, for example, A Choice In The Fog (#5) presents you with a choice of allying with either elves or human bandits against undead. This starts you on one of two different plotlines that lead to different endings. This is open branching. It's relatively simple.

Heir to the Throne has a trickier structure. There is a branch point after Bay of Pearls (#4); you can continue by land (Muff Malal's Peninsula, #5a) or by sea (Isle of the Damned, #5b). Winning either #5a and #5b takes you to Siege of Elensefar, #6.

Later in the campaign there is a three-way branch point after the aptly named A Choice Must Be Made (#18). You can fight orcs on the Snow Plains (#19a), or you can fight undead in Swamp of Dread (#19b); both these scenarios lead to Home of The North Elves (#20a). If you have mermen you can get a third option, Cliffs of Thoria (#19c). This takes you to Underground Channels (#20b). Both #20a and #20b direct you to Elven Council (#21) on victory.

These are closed branches. They rejoin the main plot when they're done. The big issue with closed branches is that the branch paths have to have about equal difficulty levels. Otherwise, you'll create a feast-or-famine instability later in the campaign because players can come to the merge point with widely varying amounts of gold.

The Rise of Wesnoth has yet another, unique, kind of branch structure which illustrates how you can get really creative. After Elf Lords (#16) there are 4 challenge scenarios: The Dragon, A Beach, Troll Hole, and Cursed Isle. You must do all four, but you get to choose the order you do them in. You loop back to Elf Lords after each victory; only completing all four lets you continue to A Spy In The Woods (#18).

It would probably be unwise to try to write a branch into your first campaign. The Hammer of Thursagan, which is my first all-original campaign (after about half a dozen adaptations for mainline), has no branches. But once you become experienced enough, branching can greatly increase your design options and the repeated play value of a campaign.

An even trickier technique than branching is changing a scenario's objectives partway through it. Handle this one with extreme care, because objective changes have a bad tendency to turn into tomato surprises (earlier we called out an example of this in Under The Burning Suns).

Never change objectives in such a way that the player can't possibly meet them without pre-planning for the new ones. As an obvious example, changing a scenario's objective to from “defeat all enemies” to “move your hero to the signpost” is quite likely to be horribly frustrating to the player — the hero might be fighting all the way on the other side of the map.

If you really must pull something like this, at least increase the scenario turn limit so the player will have time to refocus and go after the new goals.

In general, if the objectives change mid-scenario, the change should either (1) not be too difficult change strategically (perhaps as well as an extra difficulty, the player also gets assistance from somewhere), or (2) the potential for the change should be strongly hinted at to give an observant player the opportunity to plan.

Various mainline campaigns have explored different areas of the possible design space. You can learn useful things by studying them.

If you're interested in designing wargame-like campaigns with a lot of large battles, for example, study Northern Rebirth and Son of the Black-Eye. Northern Rebirth is also unusual in having lots of NPCs, and having the behavior of late-arriving NPCs be conditional on what has happened to earlier ones.

Under the Burning Suns, on the other hand, is designed to feel more like an RPG game - small-unit action, tight focus on hero and sidekicks, significant puzzle and discovery elements. Most other Wesnoth campaigns life somewhere between these extremes; Eastern Invasion and Scepter of Fire are representative of the middle.

The Rise of Wesnoth, Legend of Wesmere, Heir to the Throne, and (in an inverted way) Descent Into Darkness read like quest-fantasy novels. Story prose and character development matter more than usual in these.

Delfador's Memoirs shows how to bounce a character around between factions when this makes storyline sense. The player side swaps leaders twice and recall lists several times.

When in doubt, remember what your goal as a scenario and campaign designer is: to give your players pleasure and a sense of accomplishment. Aim for fun, not frustration.

The 1.1 version added the table of REs for common recruitment lists.

The 1.2 version added sections on Sizing maps right and Summing up to Map Composition; the old content is now Making maps interesting. Also, moved Traps to avoid to its own major section.

The 1.3 version added It's simpler than you think.

The 1.4 version added the note about THoT being essentially done in 5 weeks.

The 1.5 version added suggestions by hagabaka on how to keep large maps interesting. This inspired a new major section on adding flavor to campaigns.

The 1.6 version noted that campaign length limits should be counted in non-talk senarios.

The 1.7 version added zookeeper's material on the new gold carryover system, the inadvisability of deep-sixing veterans, and the removal of the tomato surprise in UtBS.

The 1.8 version added the section on "Examples to Study".