Hello,
Beware, this is a long one...
This is a very interessting topic. And since it appears to be of interest to the developers too, I'll try to contribute.
I also feel the campaign could greatly benefit from more dynamic elements. I think a combination of a steady, unstopable increase of the threat level over time and changes in alien tactics in response to player action might be the best way to go.
## Alien intentions and capabilities ##
First, we'll need to make a few assertions about the aliens, to be able to assess their capabilities and motivations:
- They come from a place a long way away, so resupplying is difficult. Specialty gear is hard to come by, so allround equipment needs to perform tasks for which it is not designed for practical reasons. Everything is limited in numbers, any loss of equipment, life or a vessel is a hard blow to them, not so much because of replacement cost but replacement time.
- Their goal is to take Earth with as little losses as possible, preserving as much of their and our resources as possible.
- Sun Zu tells us you have to know your enemy if you want to have a shot at victory. Since they know very little about us, their primary goal at the start of any campaign is to gain knowledge about us.
- Whenever they aquirre new intel about us, they reassess their options and plan their next moves.
- Over time their supply routes grow in capability, allowing them to field more and better equipment.
- They are intelligent, so their reaction to resistance is not merely 'throw more or tougher stuff at it', but includes changes in tactics and strategy.
## How do they win, what do they want ##
Second, we'll need to do the same for 'conquer-scenarios':
- If they erradicate all noteable resistance to them by destroying our means of defence, they have achieved their goal.
- If they break our will to fight, they have achieved their goal.
- If they infiltrate countries and win them over to their side, they have achieved their goal.
Basically those are the win-scenarios of many strategy games: military victory, domination victory (let's call it terror victory in honor of XCOM
), cultural/diplomatic victory.
## Difficulty scaling mechanism ##
Now that we have established that, let's look at a mechanism for scaling campaign difficulty:
What I propose is for the aliens to get a certain number of points at the start of each month. These represent their available NEW supplies for this month (transport capacity from their homeworld). The number grows over time and starts higher and grows faster at higher difficulty levels. They do not carry over to the following month. Each mission they decide to perform requires resources. Scout missions require scout ships, terror missions terror ships and so on. Of course battleships are much more expensive than scouts. I'm sure you get my drift. Vessels and troops need supplies, so they can't just blow all their monthly points on new stuff, they first have to pay for repair, maintenance and resupply of vessels that survived the last month. So after getting their nose bloodied particularly bad in one month the threat stays nearly the same, while if they finish a month unscathed their capabilities are increased. This should be at least partially self-balancing, since even after a month where all their vessels survive, the new ones they bring in will also have to bring supplies for themselfes AND for the surviving ones. And the next month supply costs for BOTH fleets will be deducted before new vessles can be 'ordered'. This should be fairly easy to balance by using a certain percentage of a vessles cost as their upkeep cost and adjusting this percentage with the difficulty. See [1] for an example of this. Also they would have to use each vessel at least once per month, so they can not just build up their arsenal without the player being able to do anything about it. After all, this is also in their interesst: if they don't use them they just sit there eating preacious supplies without any gain.
## Dynamic campaign elements ##
No let's add some dynamic elements to the campaign:
Now how will they decide what kind of missions they will start with their limited contingent? The basic answer to this is quite simple, they are going to compare the anticipated reward and risk.
With every mission they undertake they are trying to get closer to their goal: dominating Earth, it's resources and it's population. They can do so by either going after their objective directly or by performing missions that increase the success rate and cut back on losses of the 'objective'-missions.
Before they can decide which kind of mission they want to start, they'll need information about what kind of resistance to expect. So in a first stage of the game they'll send scouts to survey our military bases, our population centers and industrial capabilities. As they can't know how and with what kind of power we will respond they have two options at this stage: send the biggest, meanest thing they got to break anything that dares block their way (not likely, since supply routes still have to be established, making this impractical. Also, in case of a lucky hit, mechanical failure or simply the pilot screwing up they would loose a major asset and provide us with excellent intel and technology), or they could try to be stealthy and evasive (highly likely).
# Therefore in stage 1 (let's call it recon) they should run 2 kinds of missions with stealthy, small and fast ships (= small scouts):
- land in remote areas, stay as short as possible, retreat; this way they assess our social structure and gain knowledge on indigineous flora and fauna, population distribution, social order, ...
- do runs only to draw out interceptors without intention to land, retreat asap as contact is made to assess our air-to-air capabilities
# Depending on the results of stage 1 they decide on how to proceed in stage 2, combat recon:
- If they suffered only a few or no losses they have gathered enough intel and can go directly to stage 3: infiltration
- If most of their UFOs where shot down they will regognize that they will have to send tougher ships. Now if they also shot down a lot of our craft they will know we are vulnerable and will deploy lots of ships that are a bit tougher (= medium scouts). This way they can gather a lot of intel (bc of high number of ships) and still avoid losses. On the other hand if they have hardly shot down interceptors they will send fewer, tougher ships (= heavy scouts) to avoid losses, even if it means they will need more time to gather intel.
- Independent of that, if they suffered heavy losses on the ground they will send fewer ships with more numerous and/or tougher crews. Again if they decide to go for 'more' or 'tougher' will depend on the losses they have inflicted on us.
Should they again suffer heavy losses they will recognize that they will HAVE to go with a more brute-force approach and initiate stage 4 (assault), skipping stage 3 (infiltration).
# Stage 3 (infiltration):
Infiltrating your enemy, weakening him from within, dividing alliances and strong armies and conquering the pieces one by one are key concepts in warfare. So after successfully establishing our capabilities they will try to do that to us: Lure governments to their side with promises of technology, surpremacy over others, ..., pitting one against the other to gain a foothold and weaken our defences. Depending on the results of stage 1 and 2 they will use any type of scout and crew they deem appropriate and land on Earth to perform longer missions: covertly set up bases, infiltrate human society and governments. This means again they will try to avoid confrontation and try beinig stealthy (hence the scouts). Once they are content with the level of discord sown and the footholds established or once they start suffering significant enough losses they will go on to stage 4 (assault).
# Stage 4 (assault):
Now we're cooking! Basically during this stage they will try to destroy our defenses (attack our bases, try to gain air dominance by actively hunting our crafts) and subdue the governments they couldn't infiltrate in stage 3 (terror missions). Of course they'll also need to keep their bases supplied during this time (supply missions). Btw, alien bases established on Earth should provide extra resource points for the aliens and weaken nearby countries resolve. This stage can only end one of two ways: it's them or us.
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And voila, dynamic campaign with good difficulty pacing!
So now what are your thoughts on all my ramblings there?
Hope this will be of use to you and help you generate some good ideas!
Cheers,
Alex
PS: In my opinion a less linear tech tree with more sidegrading instead of upgrading and more varied paths to different-but-equal results as propsed by Bashar would be a great addition too. He's already gone into a lot of detail there, so I won't start repeating it here
, but I really like the idea of having to choose to use captured equipment and vessels either for improving Earth based technology, providing a long term benefit, or salvaging it for human use, providing a short time boost.
PPS: Some of this may also be applyable to the Battlescope (assign a certain number of points to each kind of vessel (maybe depending on mission type), each alien and each peace of equipment uses a certain amount).
PPPS ^ ^: English is not my first language, please ignore any blunders
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[1]: Supply cost example (values are completely arbitrary and not chosen for balancing but ease of calculation):
Let's say the aliens start at 18 pts per month and increase that amount by 3 pt per month. A scout vessel costs 6 points, a small scout 4, supply percentage is 50%. So in month 1 they can bring in 2 scouts plus their supplies, using all their points. The next month they get 21 pts.
If both the scouts survived then 6 will be deducted for resupply. At this point let me just quickly point out that a damaged ship's maintenance should be more expensive than the standard percentage, but never exceed 100% (they would just scrap the ship at that point). That leaves them with 15 pts for new stuff. For that they can bring in another scout and a small scout (and their supplies). So at the start of the 2nd month they have 3 scouts. If again everyone survives they will have to spend 11 of their points on supplies, leaving 13 of the 24 for new stuff -> less than the month before, the growth is self limiting.
If only one scout survived only 3 pt are deducted for supplies, so they can spend 18 on 2 new scouts, leaving them with 3, they miss out on the small scout.
If all vessels are destroyed they will only be able to get another 2 scouts for their 21 pts in month 2, but even if all vessels are destroyed again they will be able to afford 2 scouts and 1 small scout in month 3 for their 24 pts -> even if the player performs flawlessly the threat level steadily rises.
Now try changing the supply percentage to higher/lower levels and you'll see how easily you can adjust difficulty that way, without having to worry about the other variables (costs of the ships). Game designers dream: Tune one variable for balancing without breaking anything else! Ship costs can still be assined completely independent of this as a function of hitpoints, speed, range, whathaveyou, as they are now.