PDF wrote:Adding a difficulty level does not necessarily requires much balancing; you can, for example, just add or remove gold.
I'm going to argue that that is fundamentally a flawed way to balance campaigns, and should only be used in conjunction with other balancing methods.
1. Wesnoth scenarios as tactical problems
Each scenario in Wesnoth presents a tactical problem. The problem is generally phrased something like this: "Kill the enemy leader in so much time while keeping your leader alive." The most common variation is this: "Move your leader to this hex in so much time while keeping him alive." Of course, there are subtleties to these tactical problems. Because of the gold bonus you want to finish is less that the stated time. Because you can recall experienced and leveled units you want to have units that have gained experience not die. There may be other units that you must keep alive. There may be certain units you must kill. At its core, however, each scenario is a relatively simple tactical problem.
2. Factors that influence the difficulty of a tactical problem in Wesnoth
I am going to briefly list the factors (that I perceive) which affect the difficulty of a tactical problem in Wesnoth. This list is probably not exhaustive, so if there's something I've missed, post it and I'll add it to the list. They in no particular order:
b) Player's starting gold
c) AI's starting gold
d) Player's recriutment list
e) AI's recriutment list
f) Player's recall list
g) Time limitations
h) Size of player's keep
i) Size of AI's keep
j) AI Parameters (more on this in a minute)
k) Distribution of villages
Note that the AI's starting gold is one factor among many.
3. Varying the difficulty of a tactical problem presented to the player in a scenario
Considering the above factors, it is easy (if time consuming for the designer) to present tactical problems of differing difficulty in a single scenario. For most of the above factors, I'll give and example and explain in a sentence how if affects the tactical problem:
a) If the map is predominantly a terrain that favors either the player's forces or the ai's forces, it will have a huge effect on the difficulty of the battle. For example, a player whose units are broadly loyalists will have a disasterous time trying to root Elves out of woods. The terrain is, however, generally fixed by the nature of the scenario (i.e. the designer can't really make a whole new map for each difficulty level). I would submit, however, that 80% of the actual fighting in a typical scenario occurs in less than 10% of the hexes. It is possible to change only one or two hexes and have a dramatic effect on the outcome of the battle if you can identify those "chokepoint" hexes.
b) If the player has a lot of gold he can make more tactical mistakes because he can recruit more troops to replace the ones he's lost. Additionally, quantity has a quality all of its own, so if the player's starting gold is much higher that the AI's starting gold he can employ a swarm of cheap units. Note that this does not simplify the tactical problem, it only allows more mistakes to be made.
c) If the AI's starting gold is much higher than the players, the player will be unable to make any tactical mistakes and still win the scenario. I'll talk more about this in a moment.
d) If the player can only recruit units that will be effective against the enemy's forces, then the tactical problem is simplified. If I can only recruit heavy infantry to face a force of skeleton archers, then I have a less difficult tactical decision to make than if I can recruit heavy infantry and spearmen. Especially if I don't know the game well.
e) Restricting the enemy to a certain class of units (i.e. melee-only, ranged-only, impact-attacks-only) can simplify the tactical problem immensely. Bowmen are very good against thugs and thieves. If the enemy can also recruit poachers and footpads, the tactical problem becomes more difficult.
g) Again, the time limit does not allow the player to make tactical mistakes, which does not alter the problem, but makes it harder.
j) The AI parameters are perhaps the best way to alter a tactical problem. http://wesnoth.slack.it/?AiWML is a particularly important read for a scenario designer. I'd draw attention to aggression and [target] in particular. attack_depth is also very nice. These parameters are especially important for building scenarios with tactical problems that are fundamentally different from the basic kill-his-leader ones.
k) Using the [terrain] WML tag you can easily alter the distribution of villages in a scenario. Move the distribution towards the player, and things get easier. Move it towards the enemy, and they get harder.
4. Why just changing the player's and ai's starting gold is a bad idea.
Giving the enemy more gold and the player less gold certainly does make a tactical problem harder. What it doesn't do at all is change the tactical problem. At a certain point being outnumbered and outgunned just outweighs all the other factors. The tactical problem becomes "how can I defeat a force several times larger than mine?" I would argue that this has several unintended consequences.
First, it encourages save-loading. If you are so outnumbered that any mistake (or any bad luck) means that you lose the scenario, you will save load to get good luck.
Second, it overvalues higher level units. If you're outnumbered 8 to 1, an Elvish Champion for 20 gold may be your only chance. I suspect this is one of the reasons players are so keen to keep high level units around. One elvish champion can hold off 3 or 4 lower level units (which, currently, they may have to).
Third, it become boring and repetitive. At a certain point, it just isn't any fun anymore to be outnumbered and fighting for your life over and over again. The tactical problem doesn't change, it just keeps getting harder and harder, more and more frustrating.
So, let this be a call to scenario designers to incorporate variety in their tactical problems. Let it be a call for balancing to involve more than tweaking gold, because I think if scenario designers take the time to really craft varied tactical problems of varying difficulty then they will enjoy their scenarios all the more. I'm trying to do this with South Guard, and I'd love to help others do it with their campaigns.
Sorry for the tome of a post.