TL;DR
New entity that acts like a moving siege tower + nest with a number of 'passenger biters' in terms of what it can spawn when under threat or attacking.(Initially I posted this in the suggestion thread, but while re-reading this I think it would make a good mod, though with some mechanic simplifications. The suggestion below changed some small parts to be easier to script.
This topic: viewtopic.php?f=6&t=109033)
What ?
Essentially the idea is a moving nest that has biters stored up for spawning.The way it would work in game:
- Engorged centipede is unlocked by biter phase (say specific evolution level).
- An engorged centipede spawns (very small chance from nest, or where a large swarm is forming for attack and entity count needs to be reduced)
- An engorged centipede starts in absorb mode.
- Centipede 'absorbs' nearby biter entities (converts absorbed biters / spitters into stored pollution). It can only absorb undamaged targets that belong to the same force.
- Once centipede / swarm decides to attack, centipede switches to idle mode. (No more absorption.)
- While inside pollution, centipede will absorb pollution from the environment. Added to its stored pollution. Should have a high but sane max absorption rate.
- Centipede weapon should not outrange turrets. You want it to soak weapons fire and be forced to disgorge biters when it reaches defences.
- When centipede attacks an enemy, it will very slowly disgorge stored biters. Basically, no resistance = lazily destroy things with the help of a few minions. This is called attack mode.
- Centipede will, when attacked, hunker down and rapidly disgorge biters for 10 seconds (timer restarted each time it takes damage). Basically resistance = panic throw biter wave at enemies. This called hunker mode. It should be immobile during hunker mode.
- Disgorging biters means it uses stored pollution to spawn biters. Should use the same pollution 'cost' values that nests uses for biter / spitter spawning, so taking difficulty modifiers into account.
- When centipede takes damage, and it still has stored pollution, then it immediately spawns a biter instead. Regardless of any disgorge cooldowns, this is a separate 'reaction'. (Basically centipedes are effectively invulnerable while they still have stored pollution. You have to 'drain' them first before being able to kill them. And also rapid fire but low damage weapons will drain a biter rapidly, but risk getting swarmed by biters.)
- Centipede should be targetable but effectively invulnerable. Say 99% and 999999999 resistance to everything, massive health and regeneration.
- Centipede is instantly killed via script if it takes a hit but doesn't have enough stored pollution to spawn any kind of biter, even the cheapest one it can. (i.e. takes a hit but is empty of stored pollution.)
- MaxPollutionAbsorptionPerTick = The maximum amount of pollution a centipede can absorb per tick.
- InternalGrowthRatePerTick = The amount of 'pollution' the centipede gets per tick 'for free' regardless of if it is in pollution or not.
- TransportableEntitiesList = What biter and spitter types this centipede is allowed to spawn from stored pollution, and what the cost for each is.
- StoredPollution => Amount of stored pollution.
- TransportMode => Current mode. Absorb, Idle, Attack or Hunker.
Why ?
Reduces late game entity count and introduces a new type of combat mechanic that can scale well with less entity count and pathing calculations.I believe the mechanic of an 'on your door rapidly spawning nest' would make a good challenge for late game that is different from the current biter swarms.
This design also counters (to some degree) 'just mindlessly slap down more turrets', since the first entity that will come into range is the centipede. Which will draw all the fire, each hit which will spawn a new angry biter from the cargo.
At the very least it should encourage people to put a bit of thought into defence in depth, where you have some defences 'out front' meant to slow down and drain the centipedes (a use for mines?), while defences further back handle the resulting disgorged hordes.
Mod difficulty settings can adjust things like InternalGrowthRatePerTick and MaxPollutionAbsorptionPerTick, allowing the centipede to absorb more pollution as its advances on factory defences, as well as 'grow' over time even if not in pollution.