I'm thinking of a game where there are some virtual people living in a cave/underground. They mine ore, grow muchrooms and do their stuff. There are also events, among them an invasion of some monsters from the "human's world" (monsters that descend to the cave). The most similar games would be probably Dungen Keeper, Dwarf Fortress and tower defence genre.

Now, I have dilemma how to handle the invasion part. To be more precise, how the enemies descend and proceed. Since the game will be largely about mining and changing the landscape of the cave (walls, doors), the player will be able to simply block the entrance and stop the enemy progress. I know of 3 solutions to this:
- you can only destroy terrain but can't rebuild terrain, so once you digged out some part of the cave it stays open (Dungeon Keeper style)
- you always have to maintain a clear path to the "heart" of the cave which is the target point of an invasion (tower defence games)
- you can seal off yourself (simply build a wall which is inbreakable to the enemy) but it gives you such big penalties you can't afford to do it forever (Dwarf Fortress style)

Are there any other solutions I missed? Which one to choose?

You can block off the enemy, but what happens is the enemy will tunnel towards your based via an "easiest path". Used in some tower defence games, if you tried to block the path the creeps will attack your towers and attempt to punch through.

I'm thinking of a game where there are some virtual people living in a cave/underground. They mine ore, grow muchrooms and do their stuff. There are also events, among them an invasion of some monsters from the "human's world" (monsters that descend to the cave). The most similar games would be probably Dungen Keeper, Dwarf Fortress and tower defence genre.

Now, I have dilemma how to handle the invasion part. To be more precise, how the enemies descend and proceed. Since the game will be largely about mining and changing the landscape of the cave (walls, doors), the player will be able to simply block the entrance and stop the enemy progress. I know of 3 solutions to this:
- you can only destroy terrain but can't rebuild terrain, so once you digged out some part of the cave it stays open (Dungeon Keeper style)
- you always have to maintain a clear path to the "heart" of the cave which is the target point of an invasion (tower defence games)
- you can seal off yourself (simply build a wall which is inbreakable to the enemy) but it gives you such big penalties you can't afford to do it forever (Dwarf Fortress style)

Are there any other solutions I missed? Which one to choose?

I would pick a combination of the first two. Depending on how you're handling the spawns, the third option might be too hard to balance (hard to envision without an idea of the layout of the game).

If you make un-dug (not a word) terrain, unbreakable to the enemies, but allow you to refill with a 'less sturdy' landfill that the enemies can break through. This would mean extra variation to the AI since you'd have to determine whether it is more efficient to break through, or to go around obstacles. In combination with having a keep a route open to the heart of the citadel I think this could work reasonably well.



An alternative option is to allow the 'horde' to invade from somewhere other than the entrance. If you randomly determine a point somewhere near the top of the cave system and allow the enemy to 'tunnel in' there. This will create a more reactive situation to an invasion whereby the player has to figure out where/how to contain the horde within their tunnel network.

One word...MAGIC. The ever classic magic portals is always a great game design mechanic. The invaders can over-come the obstacles they face, but also gives you the chance to require your underground people need to replenish an anti-magic protective shield around their base.

There is a saying that if you are in doubt you should flip a coin. Not so you will have a quick decision to follow but because when the coin is in the mid air you will start praying for a certain result. That would be the choice you really want to choose When I read the answers, I felt sad and disappointed because no one supported the 3rd option
So, I analysed why I subconsciously hate the 1st and 2nd and it is because:
- I hate when I click on a wrong tile and the grid is digged out, never for me to fix that mistake. Also I can't change the layout later.
- I loathe the monsters/adventurers to dig out in my precious dungeon. I'm the one who is the master of this dungeon/cave and it is by my orders that my minions dig out and shape the landscape. I find it outrageous that those nasty monters could alter *my* dungeon without my permission (but I'm fine with these monsters eating my minions or pillaging rooms, I'm perfectly OK with that, which is kind of strange)
- I'm not so fond of the maintain an open path thing because in tower defence games you could sell towers and then replace them so the path changes constantly and the enemies are moving around never reaching their destination (this one probably could be fixed).

So, these are my feelings as a player. I feel this particular game should be more about shaping the dungeon/cave than repelling monster attacks. Of course the monsters that invade are an important part, you would build the dungeon with this in mind, but the majority of time you will be simply carving the interiors of your underground fortress and making a decision where the kitchen should be than repelling the ocassional invasions. I'm also OK with balance problems if that's the price for a nearly unrestricted underground fortress building.


More about the landscape. There would be probably separate 2D maps (like Dungeon Keeper) with stairs (up and down). The stairs lead to lower/upper levels of the cave. There would be like 10 of such levels. Probably the placement of these stair would be predefined and only one up and one down stair will exist on each level. Also these levels would be more like separate ecostsyems (unlike Dwarf Fortress), the cave people would be at best reluctant to go other levels and will try do meet all their need in the same level (houring, work, food). Maybe even to an extend that they can't use stairs on their own, have to be relocated to another level by the player. I also wonder if there should not be separate "local governments" (kind of like Dwarf Fortress nobles, but separate per each level of the cave).

Enemies would go from the top (invasion), that would be a regular event and the basic combat source. Also, enemies would be generatred in the bottom levels (in a form ancient beasts), these monsters would not try invade the whole cave and will stick to their original cave level (so if a player encounters a superior monsters, he could simply ignore it till he ammases forces without any penalties except of not having access to that level (and all below it)).


Also, feel free to post other things not directly related to the "invasion thing", it's a very early design stage so I'm still figuring out what exactly kind of game I want to make

So, I analysed why I subconsciously hate the 1st and 2nd and it is because:
- I hate when I click on a wrong tile and the grid is digged out, never for me to fix that mistake. Also I can't change the layout later.
- I loathe the monsters/adventurers to dig out in my precious dungeon. I'm the one who is the master of this dungeon/cave and it is by my orders that my minions dig out and shape the landscape. I find it outrageous that those nasty monters could alter *my* dungeon without my permission (but I'm fine with these monsters eating my minions or pillaging rooms, I'm perfectly OK with that, which is kind of strange)
- I'm not so fond of the maintain an open path thing because in tower defence games you could sell towers and then replace them so the path changes constantly and the enemies are moving around never reaching their destination (this one probably could be fixed).

1: Misclicking is definitely a problem sure, especially if it is impossible to undo - you could partially negate this with the ability to give orders to your minions: "dig out this section of wall" which would allow the player to see what they're going to do, before hitting the 'Go' button. Of course this would not remove the possibility of human error, and you would still be unable to change the layout of your dungeon later (something I also find quite annoying, especially if the dungeon is a long lasting structure as opposed to a short lived level)

2: The player could control/contain the invasion with use of structures primarily rather than adjusting the tunnels themselves. Putting in a series of gates/doors that can be opened and closed/locked. These could be broken through by the invading horde, but then 'repaired' by the minions once the invasion is dealt with. You restrict the horde to only travelling through the tunnels which you have built. This way the horde doesn't physically alter your layout, but they can pillage and will make a bit of a mess.

3: Generally speaking there is usually a way to abuse pathfinding in tower defence games like this. Constantly moving the 'open' route so that the monsters run back and forth and you keep them contained. Fixing this effectively would be possible but would depend on the nature of the pathfinding you are using. Since you're stating that the invasions themselves are really just a small part of the gameplay I am not sure you would want to try and find a foolproof resolution to the problem.


The reason I discounted the third option, is because I thought it would be the hardest to balance. If you have one entrance to your dungeon, the invasion can't break through the walls, then all you have to do is seal up the door and you don't have to worry about the invasion at all.

This just means that you have to balance it out however, find a reason that the player cannot simply blockade themselves in.

Option 1: The player's minions need access to the surface. This could be because you need to go and harvest materials (wood, water, something) for your base.

Option 2: The invading horde needs to be killed, not just avoided. Again, resources are the obvious answer. The invading horde drops gold which is used when building your base (or something along those lines)

Option 3: Sealing yourself off harms your base. This was actually the first one I thought of. You could introduce the aspect of airflow throughout your dungeon. The easiest way to ensure the lower levels get enough air is to have a clear route through your dungeon from the surface. If the horde invades and you seal yourself off, you'll have limited air, and eventually all your minions will die. With other options for airflow (thin air pipes to allow air to travel, but the horde can't get through) you could balance it so that a carefully planned base could choose to seal off the surface entirely, but it would need forward thinking rather than to just seal themselves in the first time the enemy attacks.

I actually think that you could introduce all three options and it could make a fairly interesting game.

One word...MAGIC. The ever classic magic portals is always a great game design mechanic. The invaders can over-come the obstacles they face, but also gives you the chance to require your underground people need to replenish an anti-magic protective shield around their base.

Hmmm, I like the overall mood of this portal/shield thing. If you have more along these lines (not necessarily fully related to the topic) please post.

2: The player could control/contain the invasion with use of structures primarily rather than adjusting the tunnels themselves. Putting in a series of gates/doors that can be opened and closed/locked. These could be broken through by the invading horde, but then 'repaired' by the minions once the invasion is dealt with. You restrict the horde to only travelling through the tunnels which you have built. This way the horde doesn't physically alter your layout, but they can pillage and will make a bit of a mess.

Yes, that's exactly what the kind of mechanic I consider ideal. Enemies do not dig the terrain but overcome the defensive posts.
Still, I'm not sure it if is possible, the player can simply build an impassable wall/undig behind the last gate...

3: Generally speaking there is usually a way to abuse pathfinding in tower defence games like this. Constantly moving the 'open' route so that the monsters run back and forth and you keep them contained. Fixing this effectively would be possible but would depend on the nature of the pathfinding you are using. Since you're stating that the invasions themselves are really just a small part of the gameplay I am not sure you would want to try and find a foolproof resolution to the problem.[/quote]Exactly, while the invasion part is an important one the whole game without invasion would still be decently playable, so I'm not willing to pay too big price to make it work perfectly... Plus I haven't seen it ressolved perfectly in any tower defence game anyway.

The reason I discounted the third option, is because I thought it would be the hardest to balance. If you have one entrance to your dungeon, the invasion can't break through the walls, then all you have to do is seal up the door and you don't have to worry about the invasion at all.

This just means that you have to balance it out however, find a reason that the player cannot simply blockade themselves in.[/quote]Well, balance is my strong point as a designer, I never had problems with it in any games. Hard to balance is definitely a price I'm rather willing to pay One quick and trivial to implement solution "your minions get -50% penalty to all tasks as long as there is an invasion army waiting outside because they are scared (and/or because the morale is low due to no access to these tasty fresh strawberries that gow in the forest they can't reach anymore because enemy blocked the entrance)".

Option 1: The player's minions need access to the surface. This could be because you need to go and harvest materials (wood, water, something) for your base.

Option 2: The invading horde needs to be killed, not just avoided. Again, resources are the obvious answer. The invading horde drops gold which is used when building your base (or something along those lines)

Option 3: Sealing yourself off harms your base. This was actually the first one I thought of. You could introduce the aspect of airflow throughout your dungeon. The easiest way to ensure the lower levels get enough air is to have a clear route through your dungeon from the surface. If the horde invades and you seal yourself off, you'll have limited air, and eventually all your minions will die. With other options for airflow (thin air pipes to allow air to travel, but the horde can't get through) you could balance it so that a carefully planned base could choose to seal off the surface entirely, but it would need forward thinking rather than to just seal themselves in the first time the enemy attacks.[/quote]In case you haven't played it, you just invented Dwarf Fortress (but instead of fresh air requirement they used rotten corpses that pollute air)


Most likely I will go for some form/combination of 3rd one. But if you have some solutions for first 2 please post, it's best for me to get the full picture of all options even if I end up not using it.

If an invasion is present, the minions are unable to move permanent walls, and have a penalty to tasks. (No fresh strawberries makes minions sad.)

Digging out and sealing in the rock is a massive undertaking, something the minions aren't really focused on when there's invading monsters or whatnot. In order to control the horde, the player can only make use of the doors/barricades which he builds, and these structures the horde can smash their way through. This grants you the option that you can restructure your base if you wish, but you need to clear out the enemy first.

This, again, could be used in conjunction with the other options. Very well, I think, with the option to always have one route open to the heart of the base. (open route would be determined by the dug-out corridors. A door would not count as a 'blocked path'.)