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Thursday, July 11, 2013

How not to design game mechanics: Lessons from CK2 combat system

The overcaffeinated Fail Bear by quinn.anya from flickr (CC-NC-SA)

I'm in the tiny minority of gamers who enjoys Paradox games. I often enjoy quite a lot of complexity in games I play - some of them like Magic: The Gathering are among the most complex games ever created (Magic's Comprehensive Rules are about 200 pages, and then add to it over 13,000 cards), and I just love discovering unusual interactions between disconnected parts of the ruleset.

Complexity in games can be not only fine, but amazing. On the other hand quite often it backfires horribly, and one really good example of such misuse of complexity is Crusader Kings 2's combat system.

How does it work

Here's a quick summary of just major CK2 combat elements by coanda. It doesn't really cover half of it like sieges, morale, army recruitment and upkeep, traits you can get in battle, chance of death during battle and so on.

Even that limited part of combat system looks really interesting at first - different unit types, multiple combat phases, interactions of different tactics, commander influence with separate commanders on each flank. Well, sure, there's the usual complaint that none of that is explained anywhere, but that's just the way Paradox games are. That's not the real problem.

The real problem is that nothing about the combat system translates to meaningful player actions.

Wait, what?

Different unit types are good against different opponents? Too bad, your demesne army is just a random mix of all unit types. Your vassals' levies? You have even less control over these mixes. Mercenaries? Almost the same story. You have a lot more control over your retinue, but then retinues are just overpowered without needing any special tactics and if a mod nerfs them down to reasonable size (like just about all of them do) they'll no longer affect your army composition significantly.

Different commanders having modifiers for unit types? Too bad again, all armies are just a random mix of everything, so it doesn't matter who you assign to lead whom.

Using terrain to give your mix of army advantage over opponent? (different unit types have different bonuses depending on terrain) The bonuses are pretty low and armies on both sides will be fairly similar mixes so it just turns into general terrain bonus equal to about their average.

And even if by some change you have perfect commander for your mix of troops - it still won't matter all that much, since he's only 1 of 3 commanders.

Basically everything a player can do other than:
  • having bigger army
  • appointing commanders with higher stats
  • defending on difficult terrain
is nearly completely worthless because hundreds of positive and negative bonuses that different parts of player's and opponent's armies get for these fancy things end averaged up to approximately zero.

The result of this highly complex system is that it leaves all players feeling that "bigger army wins" and that's they need to know.

Simple grokable systems are the answer

Meanwhile EU3 had far simpler combat system - one commander, three unit types (infantry, cavalry, and artillery - all with tech-dependent fire, shock, and morale stats), everything expressed as straightforwardly additive numbers. 

And even though EU3's system was so much simpler - it led to many interesting interactions and it wasn't outside realm of possibility to defeat armies many times larger than your own by taking advantage of the system. (with navies even more spectacular victories were achievable, but AI stupidity also had a lot to do with it)

CK2's complexity doesn't lead to wonderful scenarios like "I'm going to bait French knights harrassing them with my light cavalry, then my spearmen will ambush them in hard terrain and finish them off easily" (the kind of stuff that's so common in all Total War games) - it leads to everything getting so mixed up that it's provides far fewer actionable options than EU3.

For contrast take a look at arumba's Clear Combat mod - it basically rips out the entire tactics system out of CK2 and replaces it with a very simple system based on just commander's martial ability. Does that reduce player's ability to do interesting things? Hardly! Unless you're playing with Mongol event troops (85%-cavalry army, and most of that horse archers) or some other event troops, you can basically do all the things you did before and they'll have pretty much the same effect, except now it's all much simpler and better presented.

Complexity is not a value in itself

Complexity in games is valuable if there are ways to interact with it - if it's just an excuse to roll a thousand dice behind player's back and average the results then its existence is completely pointless.

There are so many ways to turn CK2 combat system into something that players can interact with, and much simpler at the same time. Here are just the first few ideas that come to mind:
  • Group troops in armies by type, not by levy origin. Then you could rearrange them on flanks the way you want and assign appropriate commanders to each unit type. (possible impossible to mod)
  • At least have mercenaries of just one or two unit types, with big culture specific bonuses (like retinues) so you can use them this way. (that should be very easy to mod)
  • Have very large terrain modifiers to different terrain types, so with even slightly more cavalry-heavy army you'd really want to stick to plains, while your slightly more infantry-heavy opponent would really want to stick to heavy terrain. (not too hard to mod, but AI will probably have no clue)
  • Give different unit types very different uses, for example cavalry can't siege (like in EU3), only light units can loot. (probably very hard to mod)
  • Have primary commander much larger impact over the entire battle, instead of just 1/3 of it. (I'm not sure how that works exactly)
  • Have commanders or terrain or something else controllable strongly determine length or importance of battle phases. For example in forest you have no skirmish, just instant melee, on plains skirmish is twice as long, or something like that. And I don't mean insignificant 10% bonus, but something that would make a big difference. (not sure how moddable that would be) 
  • Have an option to just harass enemy then flee. If your army is mostly light cavalry and horse archers, and their is mostly melee infantry that should let you bleed them a little at little cost then flee without actually losing the battle (and war score). Of course there should be a chance of this failing miserably if your commander is bad. (this looks doable with some heavy modding within existing tactics system)
  • Just throw the complexity away like ClearCombat and put it in some other part of the game where it can be interacted with.


Slightly_Lions said...

Hi, I found your post interesting and submitted it to the Paradox subreddit on Here's a link if you're interested.

taw said...

Slightly_Lions: I'm glad you liked my post. I hope someone figures out a good way to mod a solution to this.

Buckybone said...

The makeup of the armies isn't completely random. Different buildings within the province can increase the amount of units that come from it, and the tech level within the province effects its units' strength.

"Group troops in armies by type, not by levy origin." -- Only if the player wants to throw out the idea of leading a feudal army, where individual nobles commanded the soldiers who came from their land (and occasionally left the war early, taking their troops with them).

taw said...

Buckybone: There's a huge number of bonuses, but they're all universally completely insignificant - and even if you decided to throw all your money at building stables in all your demesne (instead of more balanced build with a lot better troop count/power to money spent ratio) - that would provide maybe a few % change in your army composition and pretty much no real difference in any actual war.

Anonymous said...

Wow. That's... truly a retarded post, by someone who didn't understand the mechanics and yet deeply feels the urge to vomit his misconceptions about it.

Troop management in CK2 is about doctrines. Of course the choices of troop types matters.
Unless you want to mash up everything to form a random and average force, you have to make a choice, and ponder who you can battle and who you can't with such a setting.

That's actually how it works in real life, and it was even truer back then.
It's a rock/paper/scissor mechanic.

You're not interested with this system and its complexity, fine, that's your choice. You want a no-brainer system, be my guest and go for it.
But don't pretend to talk down something you don't even seems to understand, while people who do and crave for richness and complexity are enjoying it.

Anonymous said...

To be fair, most of the things here are quite true. The terrain one certainly isn't; I've won many wars outnumbered with the clever use of terrain and rivers and lost multiple ones if I ignore them. According to the game, the penalty of a river crossing (IIRC) is 20%, not only a few percents! This article didn't really check its sources very well. Same goes with the traits of commanders, they are very useful... I've seen a single commander with good military strat traits win 3 flanks single-handedly, (only) losing about half of the soldiers.

taw said...

Anonymous: I'll quote you the article:

"Basically everything a player can do other than:
* having bigger army
* appointing commanders with higher stats
* defending on difficult terrain
is nearly completely worthless because hundreds of positive and negative bonuses that different parts of player's and opponent's armies get for these fancy things end averaged up to approximately zero."

I'm aware that these things have some modest combat value, unlike vast majority of modifiers.

But back to design - how much is river crossing penalty? You're saying 20% but that's incorrect. It's actually 12 different numbers for each kind of river. For small river they range from -5% to -15% on different part of the army, and that's pretty trivial. For major river it's -10% to -30%. For strait or amphibious landing it's -10% to -20%.

Tell me, why the hell didn't they put a single number on river crossing penalty? Why are they separate offence/defence penalties to every troops type? How can anybody reason about it meaningfully?

Anonymous said...

For realism. For instance, why should crossing a river meaningfully affect your archers? On the flipside, crossing a river while riding a horse is, to the best of my knowledge, impossible. As for the types, a small river might be 10 feet across, while a major river might be 100 yards, and a strait might be half a mile.

Anonymous said...

Also, it's not just for realism, but for Crusader Kings 2, they expect you to think "of course my horses will have a hard time getting across"

zoetropo said...

Taking the Battle of Hastings for comparison, individual commanders (Norman, Breton, Flemish) each brought their own "combined arms": archers, infantry and cavalry, so the centre and the two flanks ("battles") were differentiated primarily according to origin, but at the outset the ranks in depth were arranged according to function (rows of archers, infantry, then cavalry) and employed accordingly.

"I've seen a single commander with good military strat traits win 3 flanks single-handedly, (only) losing about half of the soldiers."

Harold Godwinson lost (saw killed) only half of his soldiers, but look how he ended up: chopped to pieces.

erik said...

Total War = (fairly nice) real time combat simulation with units on the battlefield
ck2 = Dynasty and feudalism simulation with Vassals u appoint who wage war for you

if u like total war more: play it and dont cry that other games arent exactly like this

type of units matter much in ck2!... effect is best noticable when u play tribesman and u want to defend the rhine against the franks with only light inf and archers. or try your castle crushing heavy infantry vs horse archers of the mongols who can reset their harass phase ad infinitum. (whooot??! wheres my melee phase)

Yea u dont want to influence the army composition of your vassals much (buying buildings for them, tho u can) but u build the army from your demesne from the scratch with different buildings which produce different types.

even with same technology lvls i beat armies twice the size of mine without (those huge) terrain modifiers cuz my war genius general held this one outnumbered flank until their morale broke due to advanced tactics he chose. i remember this outstanding victory fairly good cuz it was the first time i really was concerned about the composition, took me 10 minutes just shifting sub-troops from one flank to another. kinda looks like u didnt play deep into ck2

erik said...

no meaningful action? You mean aside from influencing state war attributes, technology, laws and relation to your vassals (which is a great factor in the possibility to raise troops) appointing generals, influencing troop composition, flank composition, chosing carefully your enemy and the stakes and prize of the war with your casus belli, calling allies to war, mending supply limits, terrain, time of attack. Even climate plays a huge role. 'bigger army wins' is simply not true, aside from the fact that ck2 is more about a rulership simulation than a war simulation.
When i played the game the first time i chose to play a small single-county count and i played 3 full generations of my dynasty without ever increasing my territory, just role-playing and learning the game

Anonymous said...

The little percentages don't average to zero unless you're an idiot and mismanage terribly. A well compositioned force taking advantage of unit type and cultural units alone can handle 2-3 to 1 odds easily, with minimal losses.

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Anonymous said...

nothing is perfect. but CK2 gets damn close to it, for me. fair enough, some things might have been done differently, but i think you are missing the point in here - this is NOT total war. this is CK2. there is much more to it than just combat

and besides - what's so wrong with combat system? it looks neat to me, and honestly, to use your own example - 1 fixed modifier for river crossing, regardless if it's a massive river or something resembling stream - are you serious?

and why would you like to have same offence/defence penalty for different troop types? i mean, they are different, did you know that?

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Anonymous said...

Funnily enough...
Group 1: 450 Heavy Cavalry, 300 Light Cavalry (3 knight retinues)
Group 2: 450 Heavy Cavalry, 300 Light Cavalry, 2000 Light Infantry, 500 Heavy Infantry, 1 Archer

Who wins? The first group, of course! Because Group 1 procs Harass and Couched Lance tactics, which give +300% and +420% damage, respectively. Group2 Procs Volley, taking good advantage of that one archer....which gives penalties to everything but that archer.