Mapmaking 101 – Balancing Invasion Scenarios

The other day I wrote an e-mail about balancing invasions that ended up being rather lengthy. So I figured I might as well clean it up, turn it into an essay, and post it here. Probably most of this is common knowledge to you all, but I’d like to think I have at least one or two original thoughts 🙂 . Anyway, I didn’t see another thread on the topic, so I hope it’s ok to start my own. I realize there’s a chance this is wholly redundant and I just didn’t see the other article. If so, just ignore.

Though I don’t think I’ve formally uploaded any here (or anywhere else), I’ve built quite a few maps over the years and have spent uncounted hours balancing and testing them. So I can pretend I at least half know what I’m talking about. All the scenarios I’ve made so far have been for personal use, but maybe if I ever get around to documenting them properly I can share a few 🙂 .

Balancing Invasion Scenarios

When you balance an invasion scenario, you’re trying to avoid two extremes:

Allowing the player to easily build such strong defenses that they can wipe out any invasion without breaking a sweat.
Making it impossible (or too difficult) for the player to acquire resources fast enough to successfully defend against attackers.

In my opinion, the former is by far the greater danger. Since there is no cost (food or gold) associated with maintaining troops once they’re trained, it’s very easy to amass an enormous army in a short period of time given moderate resource availability and a few consecutive months free from attackers. As the scenario designer, it is your job to make it difficult for the player to do this, while keeping things fun and engaging at the same time. There are two main strategies you can implement to restrict army growth: resource limits and population control. The more you utilize one the less the other is necessary, but often the best results are obtained from a combination of both.

Throughout the below, I will assume that the marketplace and merc post are either disabled or only enabled for one or two key resources, as they nearly always should be in invasion scenarios (IMO 😉 ). If you want to make a resource available for trade, make sure you carefully think through the implications on the scenario’s balance ahead of time.

Resource Limits

Perhaps the easiest way to limit troop production is to make resources scarce, either by placing very little of a resource on the map or by placing it in an inconvenient spot.

Wood. Wood is the basic foundation resource for producing buildings and weapons. As a result, it’s probably the most important one to limit. Don’t give in to the temptation to cover your map with trees. Aside from the fact that they’ll quickly reproduce and ruin visibility, this makes it too easy to commission dozens of woodcutters and build hordes of weapons in just a few months. Try to limit yourself to a couple of small groves, so the player will have to be careful not to harvest trees faster than they grow. The downside is that trees can really make a map look good, and it’s often a shame to be restrictive with them. If you do make wood readily available, be sure to implement some kind of strict population control.
Stone: If stone is easy to come by, it will be very simple for the player to wall everything in (keep, quarry, mines, farms). Maybe that’s what you want. If not, make sure you don’t make room for more than one or two quarries (depending on distance to stockpile).
Iron: Less important than the others since it has to be slowly carried in one block at a time and has limited uses. There’d have to be a lot of ore on the map before excess iron became a problem. Nevertheless, don’t go overboard.
Pitch: This one can be a real show-stopper if you’re not careful with it. A couple of big, strategically positioned pitch ditches can turn a fight you meant to be tough into a rout.
Food: This is talked about under Population Control.
Leather: Unfortunately, it’s not easy to limit leather production without limiting food production in general. If you want food to be limited you’re in luck, otherwise you still have a couple of other options. You can place a few dairy farms on the map at the beginning and not let the player build any more, but this is a bit awkward. Another option is to provide very little farmland, but lots of deer (or allow the player to buy food in the market). Finally, you can script frequent mad cow events.
Stockpile. An interesting idea I’ve never actually tried is to place just one stockpile on the map and then disable it in building availability. To some extent, this could negate the need for resource and population restrictions. There are quite a few possibilities here.
Economic goals. If the player has to stockpile a resource in order to win, less will be available for buildings and weapons. This is also an indirect population control technique.

Population Control

Unless you’re shooting for constant, all-out warfare with hundreds of troops or have made resources very scarce, you’ll need to take steps to limit population. This will (a) prevent the player from building dozens of weapons manufacturers and (b) limit the number of recruits available. There are “hard” and “soft” ways to control population:

Limited farmland, and no ability to buy food.
Place a few hovels on the map in a place that attackers can’t reach, and disable hovel-building. For a twist, put the hovels in a place attackers can reach 🙂 .
Have a “lose” event be triggered by a particular population size.
Have certain “bad” events (bandits, plague, fire) become increasingly common and severe as population grows (and let the player know this will happen).

The next three are best used in combination with one of the above:

Economic Goals. If peasants are kept busy mining and quarrying, fewer will be available for recruitment and weapons manufacture. In addition, if the player needs to stockpile wood and iron to meet economic goals, less will be available for weapons and buildings.
Fire. Frequent, unpredictable fires mean a significant number of peasants need to be kept on water duty.
Wolves/Lions/Bears. These can control the number of woodcutters and hunters that survive afield, but should only be viewed as a temporary control since the player will almost certainly exterminate them sooner or later.

Other Thoughts

The marketplace. I alluded to this briefly above, but the market makes it very easy to introduce some real pitfalls if you’re not careful. The thing to remember is that all tradable resources are equivalent from a production standpoint. That means that if you allow trading for both apples and spears, each orchard effectively becomes a (somewhat inefficient) poleturner, since at any time the player can sell off his extra apples and use the money to buy spears. In addition, any limits you’ve set up on wood availability will no longer affect spear acquisition. This may or may not be what you had in mind. The more goods you make available in the market, the more complexities and permutations you introduce and the harder it becomes to balance and test the scenario. A good general rule is not to make more than one of the resources that can be obtained directly from the map available for trade.
Mercenary post. Only enable this if you want the player to be able to quickly convert popularity (tax money) and sellable goods into troops. I practically never allow it, so I can’t comment much further.
Building and troop availability. The more buildings and troop types you make available, the more strategies will be possible and the more scenarios you’ll have to test. For example: what happens if the player uses most of their wood to make killing pits instead of bows? If they funnel their iron and pitch into a smelter instead of swordsmen and pitch ditches? If they use their iron to equip pikemen instead of swordsmen
(twice as many for the same amount of iron)? Keep the different possibilities in mind when you decide which buildings and troops to allow. If you can’t be bothered to test a particular strategy, disable the special buildings or troops that go with it.
Gold and Popularity. Popularity translates into tax money, which in turn translates into any resource enabled in the marketplace or merc post. If players use ale, religion and food to build their popularity very high, will they be able to buy resources faster than you want them to? If so, take steps to prevent this (disable churches, add a “gold acquired” win condition to limit spending, limit farmland for hops, introduce plague, fire or bandits to lower popularity, etc.). Just be careful that in taking steps to counter popularity grabs you don’t make it necessary for the player to work for maximum popularity (unless that’s what you want).
Resource locations. By scattering boulders, farmland, ore, etc. on the map, you can increase the number of troops and walls necessary to defend them. If a patch of ore is big enough to support three iron mines, it will be very easy to build a wall and gate around them, throw on a few archers, and keep raiders away. Defense will be much more difficult if you instead use three disparate patches that can support one mine each.

One major subject I haven’t talked about is matching the number and types of invading troops to the expected defenses. If there’s any interest I can do that later, or someone else could cover it 🙂
by dave_lf

Captain Tylor added some good comments to the original post.

Well for setting up invasions, you should strive to make an invasion playable on normal diffifculty, not too hard otherwise playing the invasion on very hard would be suicide. Since difficulty affects the attacking army’s numbers, Always try to achieve balance on the normal difficulty setting.

Invasions are great resource control as well. You can populate your map with lots of trees and have invasions timed just right to interrupt the woodcutters, or force the player to reconstruct their wooden palisade walls, and use up more wood than the woodcutters can cut down.

A common tactic I’ve seen in many maps is to put stone and iron resources somewhere close to the signpost, giving the invading army an extra target and forcing the player to concentrate on protecting their quarry or iron mines.

Food can be controlled by scripting a raid on the granary supply. Farms, orchards and cheese production can be further limited by scripting hops weavel, rabbit attacks and the good ol’ “mad cow” disease without the need to restrict the types of food the player can grow, minus the land itself of course.

One big thing overlooked is on the amount of invasions to set up. Deciding whether to have an invasion map last a few years or for a few decades will ultimately decide how you control resource gathering for the player. The first few invasions may cripple the player, but the stronger the economy of the castle, the easier it is to stand up to future invasions. Long, drawn out invasion scenarios reflect this more that others, so limiting the number of invasions and the win conditions can actually make the map harder for the player, since there won’t be as much time allowed for building a strong economy.

A note on the marketplace. If you allow the purchasing of ale and an inn to distribute it, the player won’t have to worry about hops farms or breweries, and just focus on buying enough ale to add that +4 to the popularity rating. If this is something you don’t want the player to do, make sure the player can’t buy ale from the marketplace.

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