Primordial cavern layer (#12)

* bring in the art assets from ClockGen's "better_caves_modpack" under CC BY 4.0,, code written from scratch.

* update mapgen_helper

* import ClockGen's giant mushroom schematics, make them and giant ferns growable

* add giant jungle mushroom, rough out actual cavern layer code framework

* fungal ceiling decorations

* decorate fungal floor a bit

* update mapgen_helper

* update primordial mushroom schematic placement to ensure it fits

* add giant mycelium fungoidal structure

* add giant mycelium to mapgen

* fix settings for giant mycelium

* make mycelium grow when players aren't present

* allow mycelium growth to pause when it hits unloaded areas

* add a use for giant mycelium

* make giant mushrooms edible, make jungle trees growable

* rough out the jungle biome

* Make a spectrum of jungle growth

* optimize pngs, add is_ground_content to everything

* use custom is_ground_content method

* fix a crash with veinstone, and simplify nvals_cave lookup now that overgen covers the same area

* more fixes for overgen support

* remove unintentional airspace from underside of slade

* fix for overgen crash in level 2

* primordial column material, add sealed shafts to underworld

* add seal block

* Set up puzzle seals to be able to dig a staircase shaft through the slade layer. TODO: the puzzle to guard the trigger.

* puzzle seals now fully functional. Need to add clues for decoding the keys next.

* add a small bit of anti-griefing - the seal breach bell only tolls globally 13 times per activation

* add flowers to the underworld warrior bones

* switch to a different key bell

* fancy up the puzzle seal temples with some custom blocks, add sub-slade grid passages

* add a clue to the seal formspec

* tweak background of inscription 2 so it's less obviously a copy of the background for inscription 1

* switch to compositing to save a few bytes

* fancy up the seal's upper surface with inscriptions to make the formspec feel consistent

* puzzle particle, bones were only spawning on top of structures

* fix ice/oil on level 3, tweak some loot probabilities

* add trail mod support

* remove deprecated files

* boost default plant growth delay, add growing selection boxes

* update map colours

* add named waypoints to the underworld

* try a more efficient way of changing the interiors of columns

* polishing up the Primordial layer

* update guide with some Primordial teasers

* updated magma sea screenshot

* update mapgen_helper and subterrane

* reduce density of megaflora a bit - was too hard to walk through

* spreading_dirt_type depends on light, create my own ABM instead

* add names to the glowing pits and some of the ruins

* separate setting for ruin markers

* record identity of slade-breachers

* make mycelia climbable

* update subterrane

* change surface tunnel detection to allow above-ground stalactites and stalagmites

* add rare thicker Goblin Caps, suitable for use as huts.

* better goblin cap schematics

* update colours

* make it slightly harder to dig down through amethyst sheathing of pits

* fixing up fungus light sensitivity, tree growth code

* fix a few minor bugs

* update deprecated functions

* add various eating sounds

* make mapping kit requirement more flexible

* update spindlestem growth code, remove deprecated functions

* fix leftover undefined variable

* add fireflies to primordial, spread out the post-mapgen node timer for plant matter a bit more.

* fix bones formspec

* add lbm to upgrade old bones

* fix slade undiggability

* make torchspines smokey and manually lightable

* fix drop definitions

* generate dry stalactites in near-surface caverns.

* caverns become far too smokey, alas

* add pitter patter of spore tree spores, alternate paper recipe

* new mapgen_helper metrics

* add smokey back to torchspine now that it can be dialed down a bit

* replace glowstone texture with a new animated one

* switch from ABM to node timer for mapgen mycelium growth

* make mapgen mycelium timer delay configurable

* improve the efficiency of giant mycelium growth using flat node array, fewer dereferences

* remove the smoke from torchspines again - it doesn't dissipate that deep underground

* give slade a more muted, gloomy hue to differentiate it from nether stone

* update screenshots with new slade colors

* update mapgen_helper

df_underworld_items/slade.lua

@@ -4,13 +4,13 @@ local S, NS = dofile(MP.."/intllib.lua")
 
 local invulnerable = df_underworld_items.config.invulnerable_slade and not minetest.settings:get_bool("creative_mode")
 
+local server_diggable_only = function(pos, player)
+	return minetest.check_player_privs(player, "server")
+end
+
 local add_immortality = function(slade_def)
 	slade_def.groups.immortal = 1
-	slade_def.groups.cracky = nil
-	--slade_def.on_destruct = function() end
-	--slade_def.can_dig = function(pos, player) return minetest.settings:get_bool("creative_mode") == true end
-	--slade_def.diggable = false
-	--slade_def.on_blast = function() end
+	slade_def.can_dig = server_diggable_only
 	return slade_def
 end
 
@@ -64,6 +64,7 @@ local slade_wall_def = {
 	paramtype = "light",
 	tiles = {"dfcaverns_slade_brick.png"},
 	walkable = true,
+	is_ground_content = false,
 	groups = { cracky=3, stone=1, level=3, slade=1, pit_plasma_resistant=1, mese_radiation_shield=1},
 	sounds = default.node_sound_stone_defaults({ footstep = { name = "bedrock2_step", gain = 1 } }),
 }
@@ -78,7 +79,7 @@ minetest.register_node("df_underworld_items:slade_sand", {
 	_doc_items_longdesc = df_underworld_items.doc.slade_desc,
 	_doc_items_usagehelp = df_underworld_items.doc.slade_usage,
 	tiles = {"dfcaverns_slade_sand.png"},
-	is_ground_content = true,
+	is_ground_content = false,
 	groups = {crumbly = 3, level = 2, falling_node = 1, slade=1, pit_plasma_resistant=1, mese_radiation_shield=1},
 	sounds = default.node_sound_gravel_defaults({
 		footstep = {name = "default_gravel_footstep", gain = 0.45},
@@ -142,10 +143,9 @@ if minetest.get_modpath("stairs") then
 	local stair_groups = {level = 3, mese_radiation_shield=1, pit_plasma_resistant=1, slade=1}
 	if invulnerable then
 		stair_groups.immortal = 1
-	else
-		stair_groups.cracky = 3
 	end
-
+	stair_groups.cracky = 3
+	
 	stairs.register_stair_and_slab(
 		"slade_brick",
 		"df_underworld_items:slade_brick",
@@ -155,6 +155,15 @@ if minetest.get_modpath("stairs") then
 		S("Slade Slab"),
 		default.node_sound_stone_defaults({ footstep = { name = "bedrock2_step", gain = 1 } })
 	)
+	
+	if invulnerable then
+		for name, def in pairs(minetest.registered_nodes) do
+			if name:sub(1,7) == "stairs:" and name:sub(-11) == "slade_brick" then
+				minetest.override_item(name, {can_dig = server_diggable_only})
+			end
+		end
+	end
+	
 end
 
 if minetest.get_modpath("mesecons_mvps") and df_underworld_items.config.invulnerable_slade then