Magma
tl;dr: made by "hot spot," melts rocks, heat can be pumped around
i think magma is too simple as it is. we need magma that is interesting and dangerous (and not just the "oops i spilled" kind of dangerous. i want the melts-through-walls kind of dangerous). having extensive magma plumbing should be more difficult than just burrowing through some stone. you should be required to line pipes with magma safe materials or be wiling to endure melting walls to move it around. there should also be the danger of eruptions from vents that cause havoc topside. settling on a magma vent should be all kinds of Fun.
*please note, all numbers made up on the spot! not guaranteed to be balanced right!*
to that end we need the following:
propagation rules:
1. needs hotspot tile at high fixed temp
2. hotspot transfers 100% of temperature to directly adjacent rock, melting it to 7/7 magma.(to make a vent, you would actually have a tower of clustered hotspots. each cluster of hotspots would have to be slightly different shape than the one on the level above and below to keep the vent from being uniform top to bottom. the magma sea would have to be a string of hotspots, or perhaps a floor. unless cut off from the source hotspot tiles will slowly regen magma)
3. new non-hotspot rock transfers 99% of temperature to next adjacent rocks, if this temperature is hot enough to melt them then they turn to 7/7 magma and retain their new 99% or origin temperature. with careful control of hotspot temperature this will allow control for varying size vents (say hello to the small offshoot vents).
4. repeat step three until the temperature is no longer able to melt a wall.
5. pumped magma retains its temp (so pumping from closer to the source is hotter and lasts longer, but can melt more tiles if not handled carefully).
6. magma cools at 2 temp points per day/month/season (except hotspots of course), but can never be less than 99% of hottest adjacent magma block. this means that all magma that is isolated from a hotspot (via pump for example) will eventually cool into rock unless it is kept circulating. magma will also increase by 1 pt per day/month/season up to 99% of its hottest adjacent tile. this will keep players from refreshing an entire pool by simply dropping in 1 hot tile of magma. it will refresh a little, but not faster than the rest of the pool is cooling.
7. hot spots are only hot if they have magma on them ( it is possible to destroy hotspots, but they will be recreated if: a. they are adjacent to a functioning hotspot, b. they are refiled with magma and c. the entire chain is connected to the "source" magma sea. this will prevent players from isolating hotspot tiles and using them in an artificially unlimited way)
Eruptions rules:
an eruption would simply be an event that generated constantly full hotspots x level above the current "vent" of hotspots
this would mean that an open vent would overflow with very hot magma, which would probably melt surrounding terrain (unless that terrain was made of magma safe rock), and would cool very slowly to rock (since it effectively started at the temp of a hotspot). you could even spawn some additional hotspot towers to widen the vent for the duration of the eruptions, but this would have to be discussed for balance (and fort destroying) issues. it would also take a considerable amount of time for the vent to cool back down to its original size.
another possibility with this method is the ability to spawn new vents dynamically from the magma sea, just start stacking up hotspots and let them melt a vent into the rock. this too would need to be discussed based on its shear fort destroying powers.
needed mechanics:
the foundation for this is already in the game, as natural ice walls already melt into 7/7 water based on temperature. this just needs to be extended to natural and constructed rock walls. the other aspect of this, temperature transfer and loss, is already partially implemented. it is for this reason that i think that it will not be a significant cpu drain above what we already have, though i am sure there would be some additional overhead (that is unless you play with temp off, in which case you are screwed).
without a
map data rewrite cooling magma that is less then 7/7 poses some issues. for this reason i propose that 6-7/7 tiles of magma cool into a full wall, 4-5/7 magma cools into a ramp 2-3/7 magma cools into a boulder and 1/7 magma cools to a floor.
Benefits:
this suggestion makes magma dynamic, rather than static. magma would be able to cool into stone on its own, as well as melt through rock and light things on fire like it should (since it will be able to transfer temp to adjacent tiles). carelessly moving magma around could cause catastrophic problems if it suddenly starts melting through important retaining walls, but keeping an isolate magma foundry would also become more difficult because you could not just pump a tile of magma to the edge of the map and expect it to last long. it would also make eruptions simple and non permanent, as isolate magma lakes will eventually cool into stone, and yet they will still be very destructive events capable of causing over 9000 damage to a fort!.
drawbacks:
slight overhead cost, but probably not significant since most systems exist in game already. noobs (as well as some unlucky pros) will roast in magmay death if they embark on an active volcano (note: this may actually be a good thing).
suggestions and comments?