Combat System for a 4X Game

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2 comments, last by Irenicuz 10 years, 6 months ago

Hello, I am creating a simple turn based 4X game and I'm currently stuck at designing a combat system that would suit the game in question.

What i want:

  • The player has no combat input (you send the army to fight, end the turn and pray for the best), possible exception are some orders adjusting the behavior of the army, for example when to retreat
  • The system is simple to enough to understand, so that player can evaluate the relative strength of the armies quickly
  • The system should encourage use of multiple types or subtypes of units, without it feeling too forced

Basically, I am trying to emulate the combat system used in Paradox games, Europa Universalis for example, but I want to add more units and troop types.

The Paradox system puts each side's units into 2 battle lines (the rest in reserve), each round units deal damage to enemy frontline units depending on their shock or fire ability (alternates between rounds). In addition artillery units can fire from second row.

Each faction just has 1 different unit for each type of troops, 1 infantry (basic unit) , 1 cavalry (big bonus in shock phase, expensive) and artillery(attack from second row, helps the unit in front on defense, extra expensive). I feel if I add a few variations of the basic unit types, I feel that the player will always choose the unit with better overall stats (or better cost efficiency) because it will yield better results, so I am looking for ways to make specialized units matter, but not be the go-to unit. For example, if you play games from the Total War series, you will want some basic units to hold the line, spearmen or pikemen to repel cavalry charges, heavy shock infantry to create pressure points in enemy lines, heavy cavalry to charge and flank, archers etc.

First idea i had was imposing some rules regarding army composition (employed by Warhammer(40k)), which enforces that each army consist of at least X percent of core units, max Y percent elite, max Z percent specialist units, max 2 same specialist units, and so on.

I was also thinking of reducing the stats of units if the number or percent in a single army goes over a cap.

But don't want to force the player to use crappy units instead of elites that he invested infrastructure in in such way, it feels dumb. "You can't have more than 2 knights in your army, cause that's how we roll around here, take some peasants instead, they want some dyin'!"

I will restrict the number of elite units that can be produced by other means of course, but I think it will just cause the player to gather them from all around the country and form a doomstack.

I was thinking of introducing more "basic unit types", that will have unique combat characteristics which will cause them to still have value despite having lesser stat numbers, for example combat formation consisting of multiple battle lines, archers can fire from backlines, spearmen can help defend the frontline units from second line, standard bearers can enhance stats of units in their line (so they are worth having in all lines).

In addition there will be of course some units better suited for fighting different faction, for example you would want to counter a faction that relies on units with heavy armor with some armor piercing units of your own.

I would love some feedback and of course more ideas on the matter, I'm sure you have some.

And thanks for reading,

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Read that one, like half of it applies to your case http://www.gamedev.net/topic/648823-ai-in-a-4x-game-combat-see-prototype-video/

Also, you might check topics started by me, I usually talk about things very similar to what you asked.

Stellar Monarch (4X, turn based, released): GDN forum topic - Twitter - Facebook - YouTube

I will restrict the number of elite units that can be produced by other means of course, but I think it will just cause the player to gather them from all around the country and form a doomstack.

In some ways I think the most interesting army variations come from how they are produced. If you gather your forces from across the land you'll get archers and footmen from the villages, heavy mercenary troops from the cities and knights from the nobles. Or something like that. Heroes of Might and Magic of all games reflected this nicely I think.
I wonder what your problem is with the doomstack. Is it the "elite units only" or the gathering of all forces into one huge army? The former can be solved by having cannon fodder valuable enough to bring along anyway. Your 20 legion doomstack is defeated by my 20 legion + 40 auxiliary legion doomstack. The latter, which a wise man once called concentration of force, is more of a strategic thing. If you don't want wars to always be "I gather my stuff, you gather your stuff and we fight in the middle" then you can make raiding very efficient. The Europa Universalis games do this to some extent, you can cause quite some harm by pillaging enemy provinces with only a few regiments. Combine it with good defensive bonuses so a smaller army can easier hold off a bigger one on home ground while your raiding parties wreck his economy.

The player has no combat input (you send the army to fight, end the turn and pray for the best), possible exception are some orders adjusting the behavior of the army, for example when to retreat.

In EU I've always wanted to tell my troops what the goal of this battle is. Is it to destroy the enemy army, to hold the province, or to delay them as long as possible so my reinforcements can arrive? In a "hold ground" scenario you would get defensive bonuses and inferior units would perform better (they'd be more dug in or on a hill or something) but the attacker could more easily retreat in good order because you wouldn't be in a good position to counter-attack. So now we have a few different situations:
Both attack: Heavy casualties, one side likely to be destroyed.
One hold ground, one attack: Heavier casualties for attacker, but defender less likely to retreat if defeated.
One delay, one attack: Somewhat heavier casualties for attacker, defender likely to be able to retreat. Slows battle down, if applicable.
One hold ground, one attack "if safe": Both sides exchange rude words and the attacker pulls back. Or something like that.

I would love some feedback and of course more ideas on the matter, I'm sure you have some.

I sure do. Like you I had the EU mechanic as a sort of baseline when thinking about this. As a general rule I wanted a little bit of a rock-paper-scissors feeling without having too much "this unit has +50% against that unit". Less gamey but the same result basically. Also the consequences should be relatively easy to understand for the player, as you said.

First of all, scouting. If you have few scouting units, primarily light cavalry, you increase the risk of being forced into a fight you don't want. And decrease the chance of catching the enemy unaware for that matter. This bonus would be capped at a certain number of scout units. By the time you have a scout in every tree it doesn't really matter if you have even more. This would be implemented by some sort of maneuver roll when an army enters the province of another army. If it falls in your favor, you get some kind of bonus, potentially a huge one. Easy number: Risk/chance of ambush.
Second of all, mobility. Light cavalry might not stand up in any kind of battle but they can just run away with very few losses. Mount & Blade illustrates this well with their Khergit(=Mongol) faction. They weren't that much more dangerous than the other factions in a fair fight, but they would never fight fair. If we where equal or I was stronger they would run away. If they where stronger I could not run away, so every fight against them was to my disadvantage, which made them terrifying.
So a more mobile army could more easily retreat in good order which is useful with delaying tactics.
In EU terms, having units that are faster than enemy units might slow them down and/or cause attrition. Enemy quick units would offset this as they fight rearguard actions. In the most extreme case, an army of heavy infantry might be able to force a pure mongol-style cavalry army to pull back 9 times out of 10, but that 1 case when it fails, the infantry army would be surrounded and destroyed. Easy numbers: Some kind of "Pursue" score for each battle which affects chance of successful retreat as well as casualties taken if the army breaks.
Thirdly, "unopposed" cavalry gets a big bonus. Cavalry facing enemy cavalry is going to be an even fight. Cavalry not facing cavalry is just going to attack the rear and cause havoc. And you only have to have some cavalry to threaten with so he just can't surround. They can still be kept in reserve. This could be simulated with a rule like: if enemy has no cavalry, my cavalry get 200% bonus, on account of being able to run around and attack any weak point they find. Combine this with the possibility of routing enemy cavalry off the field and you can now simulate the Punic war! Easy number: That 200% bonus.
Fourthly, fatigue. A fresh soldier is a lot better than an exhausted one. Your hardcore troops might have broken the enemy but they're not in any shape to pursue and destroy. Luckily, even pitchfork-peasants can stab fleeing enemies. This is a great reason to have lots of cannon fodder in reserve. Fresh recruits can also be able to protect better units for short time while they regroup so they can get back and do the real fighting.
Fifthly, formation. A formation score would reflect a units ability to withstand cavalry charges and melee fights. Capped by unit type, so pike infantry can have a very high value, light cavalry and skirmishers have a low value. Skirmishers like slingers can lower this value by being annoying without necessarily dealing or taking casualties.

Wow, that is some amazing stuff. I'll read it a couple of times and think about it. Thank you.

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