Long time reader/player, first time poster. I've been waiting for the new release to start working on a mod, but it seems like there's going to be a lot of experimentation going on first. And since a lot of people want to experiment on all sorts of little things, perhaps there should be a place for notes from experiments.
This isn't meant to be the sole basis of a mod, though I would expect that several mods would end up re-creating several of the same notes, and hopefully this thread will let us get some of the not-obvious assumptions collected together in one place. Feel free to contribute your own discoveries, or suggest quick raw changes to be tested, and I'll keep an up to date list in this post.
My discoveries:
-Creatures using the default magma template have their durability almost entirely defined by the [RELATIVE_THICKNESS:#] tag on the outer 'crust' layer. Magma men have this set to 1, and most larger creatures take one down in arena mode with little issue. Set this to 2, and they become significantly harder to drop. I tested with this creature:
[CREATURE:MAGMA_ELEPHANT]
[DESCRIPTION:Take an elephant, a huge, hairless mammal, found grazing in grasslands in groups. Now make it out of living magma.]
[NAME:magma elephant:magma elephants:magma elephant]
[CASTE_NAME:magma elephant:magma elephants:magma elephant]
[CHILD:10][GENERAL_CHILD_NAME:magma elephant calf:magma elephant calves]
[CREATURE_TILE:'E'][COLOR:4:0:1]
[FIREIMMUNE][liKES_FIGHTING][MAGMA_VISION]
[NOPAIN][EXTRAVISION][NOBREATHE][NOSTUN][NONAUSEA][NOEMOTION][NOTHOUGHT][NOEXERT]
[NO_DIZZINESS][NO_FEVERS][NO_DRINK][NO_EAT][NO_SLEEP]
[CANNOT_UNDEAD][NOT_BUTCHERABLE][NOFEAR][NOBONES][NO_THOUGHT_CENTER_FOR_MOVEMENT]
[FIXED_TEMP:12000]
[BIOME:SUBTERRANEAN_LAVA]
[UNDERGROUND_DEPTH:3:4]
[PETVALUE:1000] [PET] [MOUNT_EXOTIC] [trAINABLE]
[LARGE_ROAMING]
[POPULATION_NUMBER:15:30]
[CLUSTER_NUMBER:3:7]
[MEANDERER]
[PREFSTRING:preternatural strength]
[PREFSTRING:crusty skin]
[BODY:QUADRUPED:TAIL:2EYES:2EARS:TRUNK:2LUNGS:HEART:GUTS:ORGANS:THROAT:NECK:SPINE:BRAIN:SKULL:MOUTH:2TUSKS:GENERIC_TEETH:RIBCAGE]
[TISSUE:MAGMA]
[TISSUE_NAME:magma:NP]
[TISSUE_MATERIAL:INORGANIC:BASALT]
[TISSUE_MAT_STATE:LIQUID]
[MUSCULAR]
[FUNCTIONAL]
[STRUCTURAL]
[RELATIVE_THICKNESS:15]
[CONNECTS]
[TISSUE_SHAPE:LAYER]
[TISSUE_LAYER:BY_CATEGORY:ALL:MAGMA]
[TISSUE:CRUST]
[TISSUE_NAME:crust:NP]
[TISSUE_MATERIAL:INORGANIC:OBSIDIAN]
[TISSUE_MAT_STATE:SOLID]
[MUSCULAR]
[FUNCTIONAL]
[STRUCTURAL]
[RELATIVE_THICKNESS:1]
[CONNECTS]
[TISSUE_SHAPE:LAYER]
[TISSUE_LAYER:BY_CATEGORY:ALL:CRUST]
[BODY_SIZE:0:0:500000]
[BODY_SIZE:2:0:2500000]
[BODY_SIZE:5:0:5000000]
[BODY_APPEARANCE_MODIFIER:LENGTH:90:95:98:100:102:105:110]
[BODY_APPEARANCE_MODIFIER:HEIGHT:90:95:98:100:102:105:110]
[BODY_APPEARANCE_MODIFIER:BROADNESS:90:95:98:100:102:105:110]
[MAXAGE:50:70]
[ATTACK:KICK:BODYPART:BY_CATEGORY:FOOT_FRONT]
[ATTACK_SKILL:STANCE_STRIKE]
[ATTACK_VERB:kick:kicks]
[ATTACK_CONTACT_PERC:100]
[ATTACK_PRIORITY:MAIN]
[ATTACK_FLAG_WITH]
[ATTACK:GORE:BODYPART:BY_CATEGORY:TUSK]
[ATTACK_SKILL:BITE]
[ATTACK_VERB:gore:gores]
[ATTACK_CONTACT_PERC:100]
[ATTACK_PRIORITY:SECOND]
[ATTACK_FLAG_WITH]
[DIURNAL]
[SWIMS_INNATE][SWIM_SPEED:2500]
[MUNDANE]
Using [RELATIVE_THICKNESS:1] resulted in a quick 1- or 2-shot death against similar sized attackers, but using [RELATIVE_THICKNESS:2] made it nearly unstoppable, to the point where it had every body part broken, and was rolling on the ground pushing against a dragon to try and attack it. This may be related to the same issue with bronze colossi and undead being nearly unstoppable.
-The [DEEP_SPECIAL] tag might only apply to one material at a time. I made a quick mod where 2 materials had the tag (effectively the same as adamantine with a different name and color), and only the new one showed up in a test area. This isn't enough testing to confirm this behavior, but it leans towards the idea that the last material in a file with the [DEEP_SPECIAL] tag is the only one that the game actually treats that way.
-Tested out metal trees. Swapped the [trEE:LOCAL_PLANT_MAT:WOOD] tag on the candlenut tree to say [trEE:INORGANIC:ADAMANTINE]. The tree's color did not change to match the metal. (I think the color of trees is controlled by the [USE_MATERIAL_TEMPLATE:STRUCTURAL:STRUCTURAL_PLANT_TEMPLATE] tag). Cutting down the tree did not take any extra time, so material doesn't affect that any. The tree did drop adamantine, however it was in log form. The adamantine log appeared to have all the properties of adamantine, except it was treated as a log rather than ore/bars/wafer/thread. I made an adamantine bed, which worked like a normal bed but was ridiculously heavy. I then made adamantine training weapons, which were 36kgs vs other wooden training weapons at <1kg. I did not successfully get them to test out the training weapons, and the adamantine training weapons didn't show up at all in arena mode. I didn't see any separate entries for wood-adamantine items at all, so they may be identical to bar/wafer items.
Multi-creature civilizations: I added the [CREATURE:X] tags for humans, goblins, and ant-men to the [ENTITY: MOUNTAIN] object, and generated a new world. Modifying this object (in this way, at least) on an existing world has no effect. The results were not quite was was expected: Several more mountain halls were created, but each race kept to itself. That is, there were a couple of goblin-only mountain halls, a couple dwarf-only mountain halls, a couple antmen-only mountain halls, etc. The ant-men mountain halls only appeared in the Legends up until year 3, so I suspect they're missing a couple of tags to be playable properly. All creatures used dwarven names, since the [trANSLATION:DWARF] tag wasn't changed. No race ever had the other races within the civilization settle in the same location. In adventurer mode, all of the creatures but antmen added were playable, which isn't a change at all. Overall, it doesn't seem that this change works the way it was expected to.
Suggested/upcoming experiments:
-Edible plants being made of other materials: Will dwarves eat ice? Will they freeze doing this?
-Coins: Can we mod in our own currencies and values now? Raw tags exist, but do they work?