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mods/nether/.gitignore

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+## Generic ignorable patterns and files
+*~
+.*.swp
+debug.txt

mods/nether/LICENSE.txt

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+GPLv3 (lkloel's version)
+MIT for the changes

mods/nether/README.md

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+For a description of this Minetest mod, please refer to the forum topic:
+https://forum.minetest.net/viewtopic.php?f=9&t=10265
+
+
+TODO:
+* Mapgen: Find a way to get the perlin noise values inside [-1; 1] or use
+  another noise.
+  The problem is visible in the nether forest, where the mapgen code flattens
+  the ceiling if it is very high.
+* Mapgen: Generate more detail inside the simple pyramid-like "buildings",
+  e.g. add a small treasure chest node which contains items

mods/nether/modpack.conf

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+release = 13454
+author = Hybrid Dog
+name = nether
+description = The underworld for Minetest.
+title = Nether

mods/nether/modpack.txt

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+0

mods/nether/nether/.luacheckrc

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+read_globals = {
+	-- Defined by Minetest
+	"minetest", "vector", "PseudoRandom", "VoxelArea", "ItemStack", "dump",
+	"string",
+
+	-- Mods
+	"default", "stairs"
+}
+globals = {"nether"}
+ignore = {
+	"212",
+		-- Unused argument
+	"411", "421", "422", "423", "431", "432",
+		-- Shadowing
+}
+-- Allow very long lines in guide.lua for the HTML code
+files["guide.lua"] = {ignore = {"631"}}

mods/nether/nether/crafting.lua

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+minetest.register_craft({
+	output = "nether:fim",
+	recipe = {
+		{"nether:shroom_head"},
+		{"nether:fruit_no_leaf"},
+		{"nether:shroom_head"},
+	}
+})
+
+minetest.register_craft({
+	output = "nether:fruit_leaves",
+	recipe = {
+		{"nether:fruit_leaf", "nether:fruit_leaf", "nether:fruit_leaf"},
+		{"nether:fruit_leaf", "nether:fruit_leaf", "nether:fruit_leaf"},
+		{"nether:fruit_leaf", "nether:fruit_leaf", "nether:fruit_leaf"},
+	}
+})
+
+minetest.register_craft({
+	output = "nether:pick_mushroom",
+	recipe = {
+		{"nether:shroom_head", "nether:shroom_head", "nether:shroom_head"},
+		{"", "nether:shroom_stem", ""},
+		{"", "nether:shroom_stem", ""},
+	}
+})
+
+minetest.register_craft({
+	output = "nether:pick_wood",
+	recipe = {
+		{"nether:wood_cooked", "nether:wood_cooked", "nether:wood_cooked"},
+		{"", "group:stick", ""},
+		{"", "group:stick", ""},
+	}
+})
+
+for _,m in pairs({"netherrack", "netherrack_blue", "white"}) do
+	local input = "nether:"..m
+
+	minetest.register_craft({
+		output = "nether:pick_"..m,
+		recipe = {
+			{input, input, input},
+			{"", "group:stick", ""},
+			{"", "group:stick", ""},
+		}
+	})
+
+	minetest.register_craft({
+		output = "nether:axe_"..m,
+		recipe = {
+			{input, input},
+			{input, "group:stick"},
+			{"", "group:stick"},
+		}
+	})
+
+	minetest.register_craft({
+		output = "nether:sword_"..m,
+		recipe = {
+			{input},
+			{input},
+			{"group:stick"},
+		}
+	})
+
+	minetest.register_craft({
+		output = "nether:shovel_"..m,
+		recipe = {
+			{input},
+			{"group:stick"},
+			{"group:stick"},
+		}
+	})
+end
+
+minetest.register_craft({
+	output = "nether:netherrack_brick 4",
+	recipe = {
+		{"nether:netherrack", "nether:netherrack"},
+		{"nether:netherrack", "nether:netherrack"},
+	}
+})
+
+minetest.register_craft({
+	output = "nether:netherrack_brick_black 4",
+	recipe = {
+		{"nether:netherrack_black", "nether:netherrack_black"},
+		{"nether:netherrack_black", "nether:netherrack_black"},
+	}
+})
+
+minetest.register_craft({
+	output = "nether:netherrack_brick_blue 4",
+	recipe = {
+		{"nether:netherrack_blue", "nether:netherrack_blue"},
+		{"nether:netherrack_blue", "nether:netherrack_blue"},
+	}
+})
+
+minetest.register_craft({
+	output = "default:furnace",
+	recipe = {
+		{"nether:netherrack_brick", "nether:netherrack_brick", "nether:netherrack_brick"},
+		{"nether:netherrack_brick", "", "nether:netherrack_brick"},
+		{"nether:netherrack_brick", "nether:netherrack_brick", "nether:netherrack_brick"},
+	}
+})
+
+minetest.register_craft({
+	output = "nether:extractor",
+	recipe = {
+		{"nether:netherrack_brick", "nether:blood_top_cooked", "nether:netherrack_brick"},
+		{"nether:blood_cooked", "nether:shroom_stem", "nether:blood_cooked"},
+		{"nether:netherrack_brick", "nether:blood_stem_cooked", "nether:netherrack_brick"},
+	}
+})
+
+minetest.register_craft({
+	output = "nether:wood 4",
+	recipe = {
+		{"nether:blood_stem"},
+	}
+})
+
+minetest.register_craft({
+	output = "nether:wood_empty 4",
+	recipe = {
+		{"nether:blood_stem_empty"},
+	}
+})
+
+minetest.register_craft({
+	output = "nether:stick 4",
+	recipe = {
+		{"nether:wood_empty"},
+	}
+})
+
+minetest.register_craft({
+	output = "nether:torch",
+	recipe = {
+		{"nether:bark"},
+		{"group:stick"},
+	}
+})
+
+minetest.register_craft({
+	output = "nether:forest_wood",
+	recipe = {
+		{"nether:forest_planks", "nether:forest_planks", "nether:forest_planks"},
+		{"nether:forest_planks", "", "nether:forest_planks"},
+		{"nether:forest_planks", "nether:forest_planks", "nether:forest_planks"},
+	}
+})
+
+minetest.register_craft({
+	output = "nether:forest_planks 8",
+	recipe = {
+		{"nether:forest_wood"},
+	}
+})
+
+minetest.register_craft({
+	output = "nether:forest_planks 7",
+	recipe = {
+		{"nether:tree"},
+	},
+})
+
+local sound_allowed = true
+minetest.register_on_craft(function(itemstack, player, old_craft_grid, craft_inv)
+	if itemstack:get_name() ~= "nether:forest_planks"
+	or itemstack:get_count() ~= 7 then
+		return
+	end
+	local tree
+	for i = 1,9 do
+		if old_craft_grid[i]:get_name() == "nether:tree" then
+			tree = i
+			break
+		end
+	end
+	if not tree then	-- do nth if theres no tree
+		return
+	end
+	local rdif = math.random(-1,1)	-- add a bit randomness
+	local barkstack = ItemStack("nether:bark "..4-rdif)
+	local inv = player:get_inventory()
+	if not inv:room_for_item("main", barkstack) then	-- disallow crafting if there's not enough free space
+		craft_inv:set_list("craft", old_craft_grid)
+		itemstack:set_name("")
+		return
+	end
+	itemstack:set_count(7+rdif)
+	inv:add_item("main", barkstack)
+	if not sound_allowed then	-- avoid playing the sound multiple times, e.g. when middle mouse click
+		return
+	end
+	minetest.sound_play("default_wood_footstep", {pos=player:get_pos(),  gain=0.25})
+	sound_allowed = false
+	minetest.after(0, function()
+		sound_allowed = true
+	end)
+end)
+
+minetest.register_craft({
+	output = "default:paper",
+	recipe = {
+		{"nether:grass_dried", "nether:grass_dried", "nether:grass_dried"},
+	}
+})
+
+
+minetest.register_craft({
+	type = "cooking",
+	output = "default:coal_lump",
+	recipe = "nether:tree",
+})
+
+minetest.register_craft({
+	type = "cooking",
+	output = "nether:grass_dried",
+	recipe = "nether:grass",
+})
+
+minetest.register_craft({
+	type = "cooking",
+	output = "nether:pearl",
+	recipe = "nether:fim",
+})
+
+minetest.register_craft({
+	type = "cooking",
+	output = "nether:hotbed",
+	recipe = "nether:blood_extracted",
+})
+
+for  _,i in ipairs({"nether:blood", "nether:blood_top", "nether:blood_stem", "nether:wood"}) do
+	local cooked = i.."_cooked"
+
+	minetest.register_craft({
+		type = "cooking",
+		output = cooked,
+		recipe = i,
+	})
+
+	minetest.register_craft({
+		type = "fuel",
+		recipe = cooked,
+		burntime = 30,
+	})
+end

mods/nether/nether/furnace.lua

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+-- minetest time speed
+local time_speed = tonumber(minetest.settings:get("time_speed"))
+if not time_speed then
+	time_speed = 1
+else
+	time_speed = time_speed/72
+end
+
+local function get_date()
+	return os.date("%y %d %H %M %S")
+end
+
+-- returns the time difference in seconds
+local function get_timediff(d1, d2)
+	local d = string.split(d1, " ")
+	for n,i in pairs(string.split(d2, " ")) do
+		d[n] = i-d[n]
+	end
+	local secs = 0
+	local y,d,h,m,s = unpack(d)
+	if s ~= 0 then
+		secs = secs+s
+	end
+	if m ~= 0 then
+		secs = secs+m*60
+	end
+	if h ~= 0 then
+		secs = secs+h*3600	-- 60*60
+	end
+	if d ~= 0 then
+		secs = secs+d*86400	-- 60*60*24
+	end
+	if y ~= 0 then
+		secs = secs+y*31557600	-- 60*60*24*365.25
+	end
+	--secs = math.floor(secs+0.5)
+	if secs < 0 then
+		minetest.log("action", "play warzone2100?")
+	end
+	return secs*time_speed
+end
+
+-- copied from older default furnace code and edited a bit
+
+function nether.get_furnace_active_formspec(pos, percent)
+	local formspec =
+		"size[8,9]"..
+		"image[2,2;1,1;default_furnace_fire_bg.png^[lowpart:"..
+		(100-percent)..":default_furnace_fire_fg.png]"..
+		"list[current_name;fuel;2,3;1,1;]"..
+		"list[current_name;src;2,1;1,1;]"..
+		"list[current_name;dst;5,1;2,2;]"..
+		"list[current_player;main;0,5;8,4;]"
+	return formspec
+end
+
+nether.furnace_inactive_formspec =
+	"size[8,9]"..
+	"image[2,2;1,1;default_furnace_fire_bg.png]"..
+	"list[current_name;fuel;2,3;1,1;]"..
+	"list[current_name;src;2,1;1,1;]"..
+	"list[current_name;dst;5,1;2,2;]"..
+	"list[current_player;main;0,5;8,4;]"
+
+minetest.register_node("nether:furnace", {
+	description = "Furnace",
+	tiles = {"default_furnace_top.png", "default_furnace_bottom.png", "default_furnace_side.png",
+		"default_furnace_side.png", "default_furnace_side.png", "default_furnace_front.png"},
+	paramtype2 = "facedir",
+	groups = {cracky=2},
+	legacy_facedir_simple = true,
+	is_ground_content = false,
+	sounds = default.node_sound_stone_defaults(),
+	on_construct = function(pos)
+		local meta = minetest.get_meta(pos)
+		meta:set_string("formspec", nether.furnace_inactive_formspec)
+		meta:set_string("infotext", "Furnace")
+		local inv = meta:get_inventory()
+		inv:set_size("fuel", 1)
+		inv:set_size("src", 1)
+		inv:set_size("dst", 4)
+	end,
+	can_dig = function(pos,player)
+		local meta = minetest.get_meta(pos);
+		local inv = meta:get_inventory()
+		if not inv:is_empty("fuel") then
+			return false
+		elseif not inv:is_empty("dst") then
+			return false
+		elseif not inv:is_empty("src") then
+			return false
+		end
+		return true
+	end,
+	allow_metadata_inventory_put = function(pos, listname, index, stack, player)
+		local meta = minetest.get_meta(pos)
+		meta:set_string("last_active", get_date())
+		local inv = meta:get_inventory()
+		if listname == "fuel" then
+			if minetest.get_craft_result({method="fuel",width=1,items={stack}}).time ~= 0 then
+				if inv:is_empty("src") then
+					meta:set_string("infotext","Furnace is empty")
+				end
+				return stack:get_count()
+			else
+				return 0
+			end
+		elseif listname == "src" then
+			return stack:get_count()
+		elseif listname == "dst" then
+			return 0
+		end
+	end,
+	allow_metadata_inventory_move = function(pos, from_list, from_index, to_list, to_index, count, player)
+		local meta = minetest.get_meta(pos)
+		meta:set_string("last_active", get_date())
+		local inv = meta:get_inventory()
+		local stack = inv:get_stack(from_list, from_index)
+		if to_list == "fuel" then
+			if minetest.get_craft_result({method="fuel",width=1,items={stack}}).time ~= 0 then
+				if inv:is_empty("src") then
+					meta:set_string("infotext","Furnace is empty")
+				end
+				return count
+			else
+				return 0
+			end
+		elseif to_list == "src" then
+			return count
+		elseif to_list == "dst" then
+			return 0
+		end
+	end,
+})
+
+minetest.register_node("nether:furnace_active", {
+	description = "Furnace",
+	tiles = {
+		"default_furnace_top.png",
+		"default_furnace_bottom.png",
+		"default_furnace_side.png",
+		"default_furnace_side.png",
+		"default_furnace_side.png",
+		{
+			image = "default_furnace_front_active.png",
+			backface_culling = false,
+			animation = {
+				type = "vertical_frames",
+				aspect_w = 16,
+				aspect_h = 16,
+				length = 1.5
+			},
+		}
+	},
+	paramtype2 = "facedir",
+	light_source = 8,
+	drop = "nether:furnace",
+	groups = {cracky=2, not_in_creative_inventory=1,hot=1},
+	legacy_facedir_simple = true,
+	is_ground_content = false,
+	sounds = default.node_sound_stone_defaults(),
+	on_construct = function(pos)
+		local meta = minetest.get_meta(pos)
+		meta:set_string("formspec", nether.furnace_inactive_formspec)
+		meta:set_string("infotext", "Furnace");
+		local inv = meta:get_inventory()
+		inv:set_size("fuel", 1)
+		inv:set_size("src", 1)
+		inv:set_size("dst", 4)
+	end,
+	can_dig = function(pos,player)
+		local meta = minetest.get_meta(pos);
+		local inv = meta:get_inventory()
+		if not inv:is_empty("fuel") then
+			return false
+		elseif not inv:is_empty("dst") then
+			return false
+		elseif not inv:is_empty("src") then
+			return false
+		end
+		return true
+	end,
+	allow_metadata_inventory_put = function(pos, listname, index, stack, player)
+		local meta = minetest.get_meta(pos)
+		meta:set_string("last_active", get_date())
+		local inv = meta:get_inventory()
+		if listname == "fuel" then
+			if minetest.get_craft_result({method="fuel",width=1,items={stack}}).time ~= 0 then
+				if inv:is_empty("src") then
+					meta:set_string("infotext","Furnace is empty")
+				end
+				return stack:get_count()
+			else
+				return 0
+			end
+		elseif listname == "src" then
+			return stack:get_count()
+		elseif listname == "dst" then
+			return 0
+		end
+	end,
+	allow_metadata_inventory_move = function(pos, from_list, from_index, to_list, to_index, count, player)
+		local meta = minetest.get_meta(pos)
+		meta:set_string("last_active", get_date())
+		local inv = meta:get_inventory()
+		local stack = inv:get_stack(from_list, from_index)
+		if to_list == "fuel" then
+			if minetest.get_craft_result({method="fuel",width=1,items={stack}}).time ~= 0 then
+				if inv:is_empty("src") then
+					meta:set_string("infotext","Furnace is empty")
+				end
+				return count
+			else
+				return 0
+			end
+		elseif to_list == "src" then
+			return count
+		elseif to_list == "dst" then
+			return 0
+		end
+	end,
+})
+
+local function swap_node(pos,name)
+	local node = minetest.get_node(pos)
+	if node.name == name then
+		return
+	end
+	node.name = name
+	minetest.swap_node(pos,node)
+end
+
+minetest.register_abm({
+	nodenames = {"nether:furnace","nether:furnace_active"},
+	interval = 1.0,
+	chance = 1,
+	action = function(pos)
+		local meta = minetest.get_meta(pos)
+		if meta:get_string("timedif") == "" then
+			meta:set_float("timedif", 0.0)
+		end
+
+		-- lag shouldn't control the furnace speed
+		local current_time = get_date()
+		local last_time = meta:get_string("last_active")
+		if last_time == "" then
+			meta:set_string("last_active", current_time)
+			return
+		end
+		if last_time == current_time then
+			return
+		end
+
+		local timediff = get_timediff(last_time, current_time)+meta:get_string("timedif")
+		local times = math.floor(timediff)
+		meta:set_string("last_active", current_time)
+		meta:set_float("timedif", timediff-times)
+
+
+		for _ = 1,times do
+			for _,name in pairs({
+					"fuel_totaltime",
+					"fuel_time",
+					"src_totaltime",
+					"src_time",
+			}) do
+				if meta:get_string(name) == "" then
+					meta:set_float(name, 0.0)
+				end
+			end
+			local inv = meta:get_inventory()
+			local srclist = inv:get_list("src")
+			local cooked = nil
+			local aftercooked
+
+			if srclist then
+				cooked, aftercooked = minetest.get_craft_result({method = "cooking", width = 1, items = srclist})
+			end
+
+			local was_active = false
+
+			if meta:get_float("fuel_time") < meta:get_float("fuel_totaltime") then
+				was_active = true
+				meta:set_float("fuel_time", meta:get_float("fuel_time") + 1)
+				meta:set_float("src_time", meta:get_float("src_time") + 1)
+				if cooked
+				and cooked.item
+				and meta:get_float("src_time") >= cooked.time then
+					-- check if there's room for output in "dst" list
+					if inv:room_for_item("dst",cooked.item) then
+						-- Put result in "dst" list
+						inv:add_item("dst", cooked.item)
+						-- take stuff from "src" list
+						inv:set_stack("src", 1, aftercooked.items[1])
+					--~ else
+						--print("Could not insert '"..cooked.item:to_string().."'")
+					end
+					meta:set_string("src_time", 0)
+				end
+			end
+
+			if meta:get_float("fuel_time") < meta:get_float("fuel_totaltime") then
+				local percent = math.floor(meta:get_float("fuel_time") /
+						meta:get_float("fuel_totaltime") * 100)
+				meta:set_string("infotext","Furnace active: "..percent.."%")
+				swap_node(pos,"nether:furnace_active")
+				meta:set_string("formspec",nether.get_furnace_active_formspec(pos, percent))
+				return
+			end
+
+			local fuel = nil
+			local afterfuel
+			local cooked = nil
+			local fuellist = inv:get_list("fuel")
+			local srclist = inv:get_list("src")
+
+			if srclist then
+				cooked = minetest.get_craft_result({method = "cooking", width = 1, items = srclist})
+			end
+			if fuellist then
+				fuel, afterfuel = minetest.get_craft_result({method = "fuel", width = 1, items = fuellist})
+			end
+
+			if not fuel or fuel.time <= 0 then
+				meta:set_string("infotext","Furnace out of fuel")
+				swap_node(pos,"nether:furnace")
+				meta:set_string("formspec", nether.furnace_inactive_formspec)
+				return
+			end
+
+			if cooked.item:is_empty() then
+				if was_active then
+					meta:set_string("infotext","Furnace is empty")
+					swap_node(pos,"nether:furnace")
+					meta:set_string("formspec", nether.furnace_inactive_formspec)
+				end
+				return
+			end
+
+			meta:set_string("fuel_totaltime", fuel.time)
+			meta:set_string("fuel_time", 0)
+
+			inv:set_stack("fuel", 1, afterfuel.items[1])
+		end
+	end,
+})

mods/nether/nether/guide.lua

@@ -0,0 +1,276 @@
+-- The content of the guide
+local guide_infos = {
+	{"Nether Mushroom",
+[[Nether mushrooms can be found on the nether's ground and on Dirty Netherrack. They can be dug by hand.
+<item name=riesenpilz:nether_shroom width=100>
+
+<my_h2><b>Crafting Items</b></my_h2>
+If we drop a Nether mushroom without holding the fast key, we can split it into its stem and head. We can use them to craft a Nether Mushroom Pickaxe, a Nether Blood Extractor, and an uncooked Nether Pearl.
+<item name=nether:shroom_head width=100> <item name=nether:shroom_stem width=100>
+
+<my_h2><b>Cultivating Mushrooms</b></my_h2>
+We can get more mushrooms using Dirty Netherrack:
+1. Search a dark place (light level <= 7) and, if necessary, place Netherrack with air above it
+  <img name=nether_netherrack.png width=100>
+2. Right click with Cooked Blood onto the Netherrack to turn it into Dirty Netherrack
+  <item name=nether:hotbed width=100> <img name=nether_netherrack.png^nether_netherrack_soil.png width=100>
+3. Right click onto the Dirty Netherrack with a Nether mushroom head to add some spores
+  <item name=nether:shroom_head width=100> <img name=nether_netherrack.png^nether_netherrack_soil.png width=100>
+4. Wait
+5. Dig the Nether mushroom which grew after some time to make place for another one. After some time new spores need to be added (step 3).
+  <img name=riesenpilz_nether_shroom_side.png width=100>
+  <img name=nether_netherrack.png^nether_netherrack_soil.png width=100>
+]]},
+
+	{"Blood Structures",
+[[We can find blood structures on the ground and dig their nodes with the bare hand. They contain four kinds of nodes: Nether Blood Stem, Nether Blood, Nether Blood Head, and Nether Fruit.
+<item name=nether:blood_stem width=100> <item name=nether:blood width=100> <item name=nether:apple width=100>
+We can craft four Nether Blood Wood nodes with the stem.
+<item name=nether:wood width=100>
+The four red blood nodes can be cooked in a furnace and, except Nether Blood Wood, their blood can be extracted with a Nether Blood Extractor.
+
+<my_h2><b>Nether Fruit</b></my_h2>
+<item name=nether:apple width=100>
+Eating a Nether Fruit decreases life but it might work against hunger and give us blood:
+<item name=nether:blood_extracted width=100>
+If we eat it at the right place inside a portal, we will teleport instead of getting blood.
+If we drop it without holding the fast key, we can split it into its fruit and leaf:
+<item name=nether:fruit_leaf width=100> <item name=nether:fruit_no_leaf width=100>
+We can craft a fruit leave block out of 9 fruit leaves
+The fruit can be used to craft a nether pearl.
+<item name=nether:fruit_leaves width=100>
+A fruit leaves block
+
+<my_h2><b>Cultivating Blood Structures</b></my_h2>
+If we dig a Nether vine we get a Nether Blood Child. If this sapling is put in a dark place (light level <= 3) on top of a Nether Blood Head node, it grows into a new blood structure after some time.
+<img name=nether_sapling.png width=100>
+<img name=nether_blood.png^nether_blood_side.png width=100>
+]]},
+
+	{"Tools",
+[[We can craft five kinds of tools in the nether, which (except the Nether Mushroom Pickaxe) require sticks to be crafted. To obtain Nether Sticks we can use the Nether Blood Extractor.
+
+<my_h2><b>Nether Mushroom Pickaxe</b></my_h2>
+<item name=nether:pick_mushroom width=100>
+Strength: 1
+This pickaxe needs mushroom stems and heads to be crafted.
+
+<my_h2><b>Nether Wood Pickaxe</b></my_h2>
+<item name=nether:pick_wood width=100>
+Strength: 2
+This pickaxe can be crafted with Cooked Nether Blood Wood.
+
+<my_h2><b>Netherrack Tools</b></my_h2>
+<item name=nether:axe_netherrack width=100> <item name=nether:shovel_netherrack width=100> <item name=nether:sword_netherrack width=100> <item name=nether:pick_netherrack width=100>
+Strength: 3
+The red Netherrack tools can be crafted with usual Netherrack.
+
+<my_h2><b>Faster Tools</b></my_h2>
+<item name=nether:axe_netherrack_blue width=100> <item name=nether:shovel_netherrack_blue width=100> <item name=nether:sword_netherrack_blue width=100> <item name=nether:pick_netherrack_blue width=100>
+Strength: 3
+The blue Netherrack tools can be crafted with Blue Netherrack.
+
+<item name=nether:axe_white width=100> <item name=nether:shovel_white width=100> <item name=nether:sword_white width=100> <item name=nether:pick_white width=100>
+Strength: 3
+The Siwtonic tools can be crafted with the Siwtonic block.
+]]},
+
+	{"Cooking",
+[[To get a furnace we need to dig at least 8 Netherrack Bricks. They can be found at pyramid-like constructions and require at least a strength 1 nether pickaxe to be dug.
+To begin cooking things, we can use a mushroom or fruit to power a furnace. After that it is recommended to use cooked blood nodes.
+
+<my_h2><b>Craft Recipe</b></my_h2>
+To craft the furnace, we can use the netherrack bricks like cobble:
+<item name=nether:netherrack_brick width=100> <item name=nether:netherrack_brick width=100> <item name=nether:netherrack_brick width=100>
+<item name=nether:netherrack_brick width=100> <img name=nether_transparent.png width=100> <item name=nether:netherrack_brick width=100>
+<item name=nether:netherrack_brick width=100> <item name=nether:netherrack_brick width=100> <item name=nether:netherrack_brick width=100>
+
+<my_h2><b>Cooking Outputs</b></my_h2>
+Some nether items can be cooked, for example the Blood Structure's nodes.
+<item name=nether:blood_stem_cooked width=100> <item name=nether:blood_cooked width=100> <item name=nether:blood_top_cooked width=100> <item name=nether:wood_cooked width=100>
+Other cookable items are Blood and an item to get a Nether Pearl.
+<item name=nether:hotbed width=100> <item name=nether:pearl width=100>
+]]},
+
+	{"Nether Blood Extractor",
+[[With this extractor we can separate Blood from the Blood Structure's nodes. An alternative way to get Blood is to eat Nether Fruits. The Nether Blood Extractor enables us to obtain a Nether Blood Stem Extracted, which we can craft to (empty) Nether Wood and then to Nether Sticks.
+
+<my_h2><b>Craft Recipe</b></my_h2>
+We can craft the Nether Blood Extractor as follows:
+<item name=nether:netherrack_brick width=100> <item name=nether:blood_top_cooked width=100> <item name=nether:netherrack_brick width=100>
+<item name=nether:blood_cooked width=100> <item name=nether:shroom_stem width=100> <item name=nether:blood_cooked width=100> <img name=nether_transparent.png width=100> <item name=nether:extractor width=100>
+<item name=nether:netherrack_brick width=100> <item name=nether:blood_stem_cooked width=100> <item name=nether:netherrack_brick width=100>
+
+<my_h2><b>Usage</b></my_h2>
+We can feed the extractor with Blood to make it separate Blood from neighbouring nodes:
+1. Place the Nether Blood Extractor somewhere
+2. Place four or fewer Blood Structure's nodes next to it. Example viewed from the top:
+<img name=nether_transparent.png width=100> <img name=nether_blood_stem_top.png width=100> <img name=nether_transparent.png width=100>
+<img name=nether_blood.png width=100> <img name=nether_blood_extractor.png width=100> <img name=nether_blood.png width=100>
+<img name=nether_transparent.png width=100> <img name=nether_blood.png width=100> <img name=nether_transparent.png width=100>
+3. Right click the extractor with Blood to power it
+<img name=nether_transparent.png width=100> <img name=nether_blood_stem_top_empty.png width=100> <img name=nether_transparent.png width=100>
+<img name=nether_blood_empty.png width=100> <img name=nether_blood_extractor.png width=100> <img name=nether_blood_empty.png width=100>
+<img name=nether_transparent.png width=100> <img name=nether_blood_empty.png width=100> <img name=nether_transparent.png width=100>
+4. Take the new extracted blood and dig the extracted nodes
+]]},
+
+	{"Ores and Bricks",
+[[Digging ores requires a pickaxe from the nether of a sufficient strength. Pickaxes from the overworld do not work in general.
+
+<my_h2><b>Strength 1</b></my_h2>
+<item name=glow:stone width=100>
+The Glowing stone can be dug with pickaxes from the overworld or a pickaxe from the nether with a strenght of least one. We can find it on the nether's and nether forest's ceiling and use it for lighting.
+
+<my_h2><b>Strength 2</b></my_h2>
+<item name=nether:netherrack width=100> <item name=nether:netherrack_tiled width=100> <item name=nether:netherrack_black width=100>
+The (red) Netherrack is generated like stone, Tiled Netherrack is generated like coal ore and the Black Netherrack is generated like gravel.
+
+<my_h2><b>Strength 3</b></my_h2>
+<item name=nether:netherrack_blue width=100> <item name=nether:white width=100>
+The Blue Netherrack is generated like diamond ore and the Siwtonic block is generated like mese blocks.
+
+<my_h2><b>Bricks</b></my_h2>
+There are three types of Bricks: red, Blue, and Black Netherrack Brick. We can craft them from the corresponding Netherrack nodes and additionally, the (red) Netherrack Brick is generated in pyramid-like structures in the nether. In comparison to the Netherrack nodes, all three Bricks can be dug with a pickaxe with strength 1.
+<item name=nether:netherrack_brick width=100> <item name=nether:netherrack_brick_blue width=100> <item name=nether:netherrack_brick_black width=100>
+]]},
+
+	{"Nether Vines",
+[[Nether vines are at the ceiling of the nether and can be dug by hand. They drop Nether Blood Child nodes, from which we can grow Blood Structures. By feeding Blood to a Nether vine with air beneath it, it grows one node.
+<item name=nether:vine width=100>
+]]},
+
+	{"Portals",
+[[This nether mod supports two types of portals: the well-known Minecraft-like one made of Obsidian, and a portal which is specific to this mod. The Obsidian portal allows us to reach the nether from the overworld, but it is one-way and kills us.
+
+<my_h2><b>Build Instructions</b></my_h2>
+A nether portal requires the following nodes:
+<item name=nether:wood_empty width=100> <item name=nether:netherrack_black width=100> <item name=nether:netherrack_brick_blue width=100> <item name=nether:netherrack width=100>  <item name=nether:blood_cooked width=100> <item name=nether:apple width=100> <item name=nether:white width=100>
+* 25 (empty) Nether Wood (height 5-6)
+* 16 Black Netherrack (height 1)
+* 12 Blue Netherrack Bricks (height 2-4)
+* 8 (red) Netherrack (height 1)
+* 8 Cooked Nether Blood (height 5)
+* 4 Nether Fruits (height 4)
+* 2 Siwtonic blocks (height 1 and 5)
+
+The heights in parenthesis correspond to the relative vertical positions of the nodes. When built, the portal should look approximately like this one:
+<img name=nether_teleporter.png width=600>
+
+<my_h2><b>Usage</b></my_h2>
+Before using the portal the first time, we may want to fill our inventory with enough items so that we can build a second portal on the overworld to get back.
+We can activate the portal as follows:
+1. Stand in the middle on the Siwtonic block
+2. Eat a Nether Fruit. If the portal was built correctly, we can hear a special sound and are teleported to the overworld.
+
+If two portals in the nether and overworld have the same X and Z coordinates, they teleport us to the centre, i.e. onto the Siwtonic block, of the opposite portal when eating a Nether Fruit.
+]]},
+
+	{"Pearls",
+[[The nether pearl can be used to teleport by throwing it.
+
+<my_h2><b>Craft Recipe</b></my_h2>
+First, we need to craft two Nether Mushroom Heads and a Nether Fruit Without Leaf together as follows:
+<item name=nether:shroom_head width=100>
+<item name=nether:fruit_no_leaf width=100>
+<item name=nether:shroom_head width=100>
+This gives us the Nether Fruit in Mushroom (FIM), which we can cook in a furnace to obtain a Nether Pearl.
+<item name=nether:fim width=100> <item name=nether:pearl width=100>
+]]},
+
+	{"Nether Forest",
+[[The nether forest is generated in caves above the nether and contains decorative plants.
+
+<my_h2><b>Grass and Flower</b></my_h2>
+<item name=nether:grass_big width=100> <item name=nether:grass_middle width=100> <item name=nether:grass_small width=100>
+We can craft the Nether Grass item to another grass item, which can be cooked to get Dried Nether Grass. We can then craft this dried grass to paper.
+
+<item name=nether:glowflower width=100>
+The Glowing Flower can be used for lighting and decoration.
+
+<my_h2><b>Nether Tree</b></my_h2>
+<item name=nether:tree width=100>
+Nether trunks can be found at Nether Trees and be crafted into Nether Wood Blocks via Nether Wood Planks. Furthermore, the Nether Tree Saplings grow even in the overworld if they have Nether Dirt beneath them.
+]]}
+}
+
+-- The guide formspecs
+local guide_forms = {}
+
+-- Convert the guide content to formspecs
+for n,data in ipairs(guide_infos) do
+	local title, html_content = data[1], data[2]
+	--~ local html_text = "<global background=#242424 size=24><tag name=my_h1 size=35>" ..
+	local html_text = "<global size=24><tag name=my_h1 size=35>" ..
+		"<tag name=my_h2 size=30>" ..
+		"<my_h1><b><center>" .. title .. "</b></center></my_h1>\n" ..
+		html_content
+	local spec_width = 16
+	local spec_height = 16
+	local html_padding = 0.5
+	local form = ("formspec_version[4]size[%g,%g;]" ..
+			"hypertext[%g,%g;%g,%g;html;%s]button[%g,%g;2,0.8;quit;Back]"
+		):format(
+		spec_width, spec_height,
+		html_padding, html_padding,
+		spec_width - 2 * html_padding, spec_height - 1 - 2 * html_padding,
+		minetest.formspec_escape(html_text),
+		0.5 * spec_width - 1, spec_height - 1)
+
+	guide_forms[n] = {title, form}
+end
+
+local title_to_index = {}
+for n, i in ipairs(guide_forms) do
+	title_to_index[i[1]] = n
+end
+
+-- Create the contents formspec
+guide_forms.contents = "formspec_version[4]size[6," .. (#guide_infos) + 2 ..
+	";]label[2,0.8;Contents:]"
+for i, data in ipairs(guide_forms) do
+	local desc = data[1]
+	local y = i + 0.5 + 0.1
+	guide_forms.contents = guide_forms.contents ..
+		"button[0.5," .. y .. ";5,0.8;name;" .. desc .. "]"
+end
+
+minetest.register_on_player_receive_fields(function(player, formname, fields)
+	if formname == "nether_guide_contents" then
+		local fname = fields.name
+		local pname = player:get_player_name()
+		if fname
+		and pname then
+			minetest.show_formspec(pname, "nether_guide",
+				guide_forms[title_to_index[fname]][2])
+		end
+	elseif formname == "nether_guide" then
+		local fname = fields.quit
+		local pname = player:get_player_name()
+		if fname
+		and pname then
+			minetest.show_formspec(pname, "nether_guide_contents",
+				guide_forms["contents"])
+		end
+	end
+end)
+
+minetest.register_chatcommand("nether_help", {
+	params = "",
+	description = "Shows a nether guide",
+	func = function(name)
+		local player = minetest.get_player_by_name(name)
+		if not player then
+			return false, "Something went wrong."
+		end
+		if not nether.overworld_help and player:get_pos().y > nether.start then
+			return false, "Usually you don't neet this guide here. " ..
+				"You can view it in the nether."
+		end
+		minetest.chat_send_player(name, "Showing guide...")
+		-- Show the Contents (overview) page
+		minetest.show_formspec(name, "nether_guide_contents",
+			guide_forms["contents"])
+		return true
+	end
+})

mods/nether/nether/mod.conf

@@ -0,0 +1,3 @@
+name = nether
+depends = default,glow,riesenpilz
+optional_depends = creative,fence_registration,function_delayer,stairs,watershed

mods/nether/nether/pearl.lua

@@ -0,0 +1,190 @@
+
+local function throw_pearl(item, player)
+	local playerpos = player:get_pos()
+	playerpos.y = playerpos.y+1.625
+	local obj = minetest.add_entity(playerpos, "nether:pearl_entity")
+	local dir = player:get_look_dir()
+	obj:set_velocity(vector.multiply(dir, 30))
+	obj:set_acceleration({x=dir.x*-3, y=-dir.y^8*80-10, z=dir.z*-3})
+	local pname = player:get_player_name()
+	obj:get_luaentity().player = pname
+	if not minetest.is_creative_enabled(pname) then
+		item:take_item()
+		return item
+	end
+end
+
+local function get_node(pos)
+	local name = minetest.get_node(pos).name
+	if name ~= "ignore" then
+		return name
+	end
+	minetest.get_voxel_manip():read_from_map(pos, pos)
+	name = minetest.get_node_or_nil(pos)
+	if not name then
+		return
+	end
+	return name.name
+end
+
+local softs = {}
+local function is_soft(pos)
+	local name = get_node(pos)
+	if not name then
+		return false
+	end
+	local is_soft = softs[name]
+	if is_soft ~= nil then
+		return is_soft
+	end
+	if not minetest.registered_nodes[name] then
+		softs[name] = false
+		return false
+	end
+	is_soft = minetest.registered_nodes[name].walkable == false
+	softs[name] = is_soft
+	return is_soft
+end
+
+-- teleports the player there if there's free space
+local function teleport_player(pos, player)
+	if not is_soft(pos) then
+		return false
+	end
+	if not is_soft({x=pos.x, y=pos.y+1, z=pos.z})
+	and not is_soft({x=pos.x, y=pos.y-1, z=pos.z}) then
+		return false
+	end
+	pos.y = pos.y+0.05
+	player:move_to(pos)
+	return true
+end
+
+--[[
+local dg_ps = {}
+local function forceload(pos)
+	dg_ps[#dg_ps+1] = pos
+	minetest.forceload_block(pos)
+	minetest.after(5, function(pos)
+		minetest.forceload_free_block(pos)
+		for i,p in pairs(dg_ps) do
+			if vector.equals(p, pos) then
+				dg_ps[i] = nil
+				return
+			end
+		end
+	end, pos)
+end
+minetest.register_on_shutdown(function()
+	for _,p in pairs(dg_ps) do
+		minetest.forceload_free_block(p)
+	end
+end)--]]
+
+minetest.register_entity("nether:pearl_entity", {
+	collisionbox = {0,0,0,0,0,0}, --not pointable
+	visual_size = {x=0.1, y=0.1},
+	physical = false, -- Collides with things
+	textures = {"nether_pearl.png"},
+	on_activate = function(self, staticdata)
+		if not staticdata
+		or staticdata == "" then
+			return
+		end
+		local tmp = minetest.deserialize(staticdata)
+		if not tmp then
+			minetest.log("error", "[nether] pearl: invalid staticdata ")
+			return
+		end
+		self.player = tmp.player
+	end,
+	get_staticdata = function(self)
+		--forceload(vector.round(self.object:get_pos()))
+		return minetest.serialize({
+			player = self.player,
+		})
+	end,
+	timer = 0,
+	on_step = function(self, dtime)
+		self.timer = self.timer+dtime
+
+	--[[
+		local delay = self.delay
+		if delay < 0.1 then
+			self.delay = delay+dtime
+			return
+		end
+		self.delay = 0--]]
+
+		if self.timer > 20 then
+			self.object:remove()
+			return
+		end
+
+		local pos = self.object:get_pos()
+		local rpos = vector.round(pos)
+		local lastpos = self.lastpos
+		if not lastpos then
+			self.lastpos = vector.new(rpos)
+			return
+		end
+		if lastpos.x
+		and vector.equals(vector.round(lastpos), rpos) then
+			return
+		end
+
+		local player = self.player
+		if not player then
+			minetest.log("error", "[nether] pearl: missing playername")
+			self.object:remove()
+			return
+		end
+		player = minetest.get_player_by_name(player)
+		if not player then
+			minetest.log("error", "[nether] pearl: missing player")
+			self.object:remove()
+			return
+		end
+
+		if not get_node(rpos) then
+			minetest.log("error", "[nether] pearl: missing node")
+			self.object:remove()
+			return
+		end
+
+		self.lastpos = vector.new(pos)
+
+		local free, p = minetest.line_of_sight(lastpos, pos)
+		if free then
+			return
+		end
+		if is_soft(p) then
+			return
+		end
+		self.object:remove()
+		minetest.after(0, function(p) --minetest.after is used that the sound is played after the teleportation
+			minetest.sound_play("nether_pearl", {pos=p, max_hear_distance=10})
+		end, p)
+		p.y = p.y+1
+		if teleport_player(vector.new(p), player) then
+			return
+		end
+		p.y = p.y-2
+		for i = -1,1,2 do
+			for _,j in pairs({{i, 0}, {0, i}}) do
+				if teleport_player({x=p.x+j[1], y=p.y, z=p.z+j[2]}, player) then
+					return
+				end
+			end
+		end
+		for i = -1,1,2 do
+			for j = -1,1,2 do
+				if teleport_player({x=p.x+j, y=p.y, z=p.z+i}, player) then
+					return
+				end
+			end
+		end
+	end
+})
+
+minetest.override_item("nether:pearl", {on_use = throw_pearl})

mods/nether/nether/portal.lua

@@ -0,0 +1,697 @@
+--code copied from Pilzadam's nether mod and edited
+
+-- kills the player if he uses PilzAdam portal
+local portal_target = nether.buildings+1
+local damage_enabled = minetest.settings:get_bool"enable_damage"
+local mclike_portal = false
+
+local abm_allowed
+minetest.after(5, function()
+	abm_allowed = true
+end)
+
+local save_path = minetest.get_worldpath() .. "/nether_players"
+local players_in_nether = {}
+
+-- Load the list of players which are trapped in the nether
+-- (or would be trapped if nether.trap_players was true)
+do
+	local file = io.open(save_path, "r")
+	if file then
+		local contents = file:read"*all"
+		io.close(file)
+		if contents then
+			local playernames = string.split(contents, " ")
+			for i = 1,#playernames do
+				players_in_nether[playernames[i]] = true
+			end
+		end
+	end
+end
+
+local function save_nether_players()
+	local playernames,n = {},1
+	for name in pairs(players_in_nether) do
+		playernames[n] = name
+		n = n+1
+	end
+	local f = io.open(save_path, "w")
+	assert(f, "Could not open nether_players file for writing.")
+	f:write(table.concat(playernames, " "))
+	io.close(f)
+end
+
+local update_background
+if nether.trap_players then
+	function update_background(player, down)
+		if down then
+			player:set_sky({r=15, g=0, b=0}, "plain")
+		else
+			player:set_sky(nil, "regular")
+		end
+	end
+else
+	function update_background()end
+end
+
+-- returns nodename if area is generated, else calls generation function
+local function generated_or_generate(pos)
+	local node = minetest.get_node_or_nil(pos)
+	if node then
+		return node.name
+	end
+	minetest.get_voxel_manip():read_from_map(pos, pos)
+	node = minetest.get_node_or_nil(pos)
+	if not node then
+		minetest.emerge_area(vector.subtract(pos, 80), vector.add(pos, 80))
+		return false
+	end
+	return node.name
+end
+
+-- where the player appears after dying
+local function get_player_died_target(player)
+	local target = vector.add(player:get_pos(),
+		{x=math.random(-100,100), y=0, z=math.random(-100,100)})
+	target.y = portal_target + math.random(4)
+	return target
+end
+
+-- used for obsidian portal
+local function obsidian_teleport(player, pname, target)
+	minetest.chat_send_player(pname, "For any reason you arrived here. Type " ..
+		"/nether_help to find out things like craft recipes.")
+	players_in_nether[pname] = true
+	save_nether_players()
+	update_background(player, true)
+	if target then
+		player:set_pos(target)
+	else
+		player:set_hp(0)
+	end
+end
+
+-- teleports players to nether or helps it
+local function player_to_nether(player, pos)
+	local pname = player:get_player_name()
+	players_in_nether[pname] = true
+	save_nether_players()
+	update_background(player, true)
+	if pos then
+		player:set_pos(pos)
+		return
+	end
+	minetest.chat_send_player(pname, "For any reason you arrived here. " ..
+		"Type /nether_help to find out things like craft recipes.")
+	if nether.trap_players then
+		player:set_hp(0)
+	end
+	if not damage_enabled or not nether.trap_players then
+		player:set_pos(get_player_died_target(player))
+	end
+end
+
+local function player_from_nether(player, pos)
+	local pname = player:get_player_name()
+	if players_in_nether[pname] then
+		players_in_nether[pname] = nil
+		save_nether_players()
+	end
+	update_background(player, false)
+	player:set_pos(pos)
+end
+
+
+local function player_exists(name)
+	local players = minetest.get_connected_players()
+	for i = 1,#players do
+		if players[i]:get_player_name() == name then
+			return true
+		end
+	end
+	return false
+end
+
+-- Chatcommands (edited) written by sss
+minetest.register_chatcommand("to_hell", {
+	params = "[<player_name>]",
+	description = "Send someone to hell",
+	func = function(name, pname)
+		if not minetest.check_player_privs(name, {nether=true}) then
+			return false,
+				"You need the nether privilege to execute this chatcommand."
+		end
+		if not player_exists(pname) then
+			pname = name
+		end
+		local player = minetest.get_player_by_name(pname)
+		if not player then
+			return false, "Something went wrong."
+		end
+		minetest.chat_send_player(pname, "Go to hell !!!")
+		player_to_nether(player)
+		return true, pname.." is now in the nether."
+	end
+})
+
+minetest.register_chatcommand("from_hell", {
+	params = "[<player_name>]",
+	description = "Extract from hell",
+	func = function(name, pname)
+		if not minetest.check_player_privs(name, {nether=true}) then
+			return false,
+				"You need the nether priv to execute this chatcommand."
+		end
+		if not player_exists(pname) then
+			pname = name
+		end
+		local player = minetest.get_player_by_name(pname)
+		if not player then
+			return false, "Something went wrong."
+		end
+		minetest.chat_send_player(pname, "You are free now")
+		local pos = player:get_pos()
+		player_from_nether(player, {x=pos.x, y=100, z=pos.z})
+		return true, pname.." is now out of the nether."
+	end
+})
+
+
+-- Disallow teleportation and change spawn positions if the nether traps players
+if nether.trap_players then
+	-- randomly set player position when he/she dies in nether
+	minetest.register_on_respawnplayer(function(player)
+		local pname = player:get_player_name()
+		if not players_in_nether[pname] then
+			return
+		end
+		local target = get_player_died_target(player)
+		player:set_pos(target)
+		minetest.after(0, function(pname, target)
+			-- fixes respawn bug
+			local player = minetest.get_player_by_name(pname)
+			if player then
+				player:move_to(target)
+			end
+		end, pname, target)
+		return true
+	end)
+
+	-- override set_pos etc. to disallow player teleportion by e.g. travelnet
+	local function can_teleport(player, pos)
+		if not player:is_player() then
+			-- the same metatable is used for entities
+			return true
+		end
+		local pname = player:get_player_name()
+		local in_nether = players_in_nether[pname] == true
+
+		-- test if the target is valid
+		if pos.y < nether.start then
+			if in_nether then
+				return true
+			end
+		elseif not in_nether then
+			return true
+		end
+
+		-- test if the current position is valid
+		local current_pos = player:get_pos()
+		local now_in_nether = current_pos.y < nether.start
+		if now_in_nether ~= in_nether then
+			if in_nether then
+				minetest.log("action", "Player \"" .. pname ..
+					"\" has to be in the nether, teleporting it!")
+				update_background(player, true)
+				current_pos.y = portal_target
+				player:set_pos(current_pos)
+			else
+				minetest.log("action", "Player \"" .. pname ..
+					"\" must not be in the nether, teleporting it!")
+				update_background(player, false)
+				current_pos.y = 20
+				player:set_pos(current_pos)
+			end
+			return false
+		end
+
+		minetest.chat_send_player(pname,
+			"You can not simply teleport to or from the nether!")
+		minetest.log("action", "Player \"" .. pname ..
+			"\" attempted to teleport from or to the nether, ignoring.")
+		return false
+	end
+	local methods = {"set_pos", "move_to", "setpos", "moveto"}
+	local metatable_overridden
+	minetest.register_on_joinplayer(function(player)
+		-- set the background when the player joins
+		if player:get_pos().y < nether.start then
+			update_background(player, true)
+		end
+
+		-- overide set_pos etc. if not yet done
+		if metatable_overridden then
+			return
+		end
+		metatable_overridden = true
+		local mt = getmetatable(player)
+		for i = 1,#methods do
+			local methodname = methods[i]
+			local origfunc = mt[methodname]
+			mt[methodname] = function(...)
+				if can_teleport(...) then
+					origfunc(...)
+				end
+			end
+		end
+	end)
+end
+
+-- removes the violet stuff from the obsidian portal
+local function remove_portal_essence(pos)
+	for z = -1,1 do
+		for y = -2,2 do
+			for x = -1,1 do
+				local p = {x=pos.x+x, y=pos.y+y, z=pos.z+z}
+				if minetest.get_node(p).name == "nether:portal" then
+					minetest.remove_node(p)
+				end
+			end
+		end
+	end
+end
+
+-- change parts of the particledefinition instead of recreating it every time
+local particledef = {
+	amount = 32,
+	time = 4,
+	minvel = {x=0, y=1, z=0},
+	maxvel = {x=0, y=2, z=0},
+	minacc = {x=-0.5,y=-3,z=-0.3},
+	maxacc = {x=0.5,y=-0.4,z=0.3},
+	minexptime = 1,
+	maxexptime = 1,
+	minsize = 0.4,
+	maxsize = 3,
+	collisiondetection = true,
+}
+
+-- teleports player to neter (obsidian portal)
+local function obsi_teleport_player(player, pos, target)
+	local pname = player:get_player_name()
+	if players_in_nether[pname] then
+		return
+	end
+
+	local objpos = player:get_pos()
+	objpos.y = objpos.y+0.1 -- Fix some glitches at -8000
+	if minetest.get_node(vector.round(objpos)).name ~= "nether:portal" then
+		return
+	end
+
+	local has_teleported
+	if damage_enabled then
+		obsidian_teleport(player, pname)
+		has_teleported = true
+	elseif not mclike_portal then
+		local target = vector.round(get_player_died_target(player))
+		if generated_or_generate(target) then
+			obsidian_teleport(player, pname, target)
+			has_teleported = true
+		end
+	end
+
+	if not has_teleported then
+		-- e.g. ungenerated area
+		return
+	end
+
+	remove_portal_essence(pos)
+
+	minetest.sound_play("nether_portal_usual", {to_player=pname, gain=1})
+end
+
+-- abm for particles of the obsidian portal essence and for teleporting
+minetest.register_abm({
+	nodenames = {"nether:portal"},
+	interval = 1,
+	chance = 2,
+	catch_up = false,
+	action = function(pos, node)
+		if not abm_allowed then
+			return
+		end
+		particledef.minpos = {x=pos.x-0.25, y=pos.y-0.5, z=pos.z-0.25}
+		particledef.maxpos = {x=pos.x+0.25, y=pos.y+0.34, z=pos.z+0.25}
+		particledef.texture = "nether_portal_particle.png^[transform" ..
+			math.random(0, 7)
+		minetest.add_particlespawner(particledef)
+		for _,obj in pairs(minetest.get_objects_inside_radius(pos, 1)) do
+			if obj:is_player() then
+				local meta = minetest.get_meta(pos)
+				local target = minetest.string_to_pos(meta:get_string("target"))
+				if target then
+					minetest.after(3, obsi_teleport_player, obj, pos, target)
+				end
+			end
+		end
+	end,
+})
+
+local function move_check(p1, max, dir)
+	local p = {x=p1.x, y=p1.y, z=p1.z}
+	local d = math.abs(max-p1[dir]) / (max-p1[dir])
+	while p[dir] ~= max do
+		p[dir] = p[dir] + d
+		if minetest.get_node(p).name ~= "default:obsidian" then
+			return false
+		end
+	end
+	return true
+end
+
+local function check_portal(p1, p2)
+	if p1.x ~= p2.x then
+		if not move_check(p1, p2.x, "x") then
+			return false
+		end
+		if not move_check(p2, p1.x, "x") then
+			return false
+		end
+	elseif p1.z ~= p2.z then
+		if not move_check(p1, p2.z, "z") then
+			return false
+		end
+		if not move_check(p2, p1.z, "z") then
+			return false
+		end
+	else
+		return false
+	end
+
+	if not move_check(p1, p2.y, "y") then
+		return false
+	end
+	if not move_check(p2, p1.y, "y") then
+		return false
+	end
+
+	return true
+end
+
+-- tests if it's an obsidian portal
+local function is_portal(pos)
+	for d=-3,3 do
+		for y=-4,4 do
+			local px = {x=pos.x+d, y=pos.y+y, z=pos.z}
+			local pz = {x=pos.x, y=pos.y+y, z=pos.z+d}
+			if check_portal(px, {x=px.x+3, y=px.y+4, z=px.z}) then
+				return px, {x=px.x+3, y=px.y+4, z=px.z}
+			end
+			if check_portal(pz, {x=pz.x, y=pz.y+4, z=pz.z+3}) then
+				return pz, {x=pz.x, y=pz.y+4, z=pz.z+3}
+			end
+		end
+	end
+end
+
+-- put here the function for creating a second portal
+local create_second_portal
+if mclike_portal then
+	function create_second_portal(target)
+		-- change target here
+	end
+end
+
+-- adds the violet portal essence
+local function make_portal(pos)
+	local p1, p2 = is_portal(pos)
+	if not p1
+	or not p2 then
+		print("[nether] something failed.")
+		return false
+	end
+
+	local in_nether = p1.y < nether.start
+
+	if in_nether
+	and not mclike_portal then
+		print("[nether] aborted, obsidian portals can't be used to get out")
+		return
+	end
+
+	for d=1,2 do
+	for y=p1.y+1,p2.y-1 do
+		local p
+		if p1.z == p2.z then
+			p = {x=p1.x+d, y=y, z=p1.z}
+		else
+			p = {x=p1.x, y=y, z=p1.z+d}
+		end
+		if minetest.get_node(p).name ~= "air" then
+			return false
+		end
+	end
+	end
+
+	local param2
+	if p1.z == p2.z then
+		param2 = 0
+	else
+		param2 = 1
+	end
+
+	local target = {x=p1.x, y=p1.y, z=p1.z}
+	target.x = target.x + 1
+	if in_nether then
+		target.y = 0
+		create_second_portal(target)
+	else
+		target.y = portal_target + math.random(4)
+	end
+
+	if not generated_or_generate(target)
+	and mclike_portal then
+		return false
+	end
+
+	for d=0,3 do
+	for y=p1.y,p2.y do
+		local p
+		if param2 == 0 then
+			p = {x=p1.x+d, y=y, z=p1.z}
+		else
+			p = {x=p1.x, y=y, z=p1.z+d}
+		end
+		if minetest.get_node(p).name == "air" then
+			minetest.set_node(p, {name="nether:portal", param2=param2})
+		end
+		local meta = minetest.get_meta(p)
+		meta:set_string("p1", minetest.pos_to_string(p1))
+		meta:set_string("p2", minetest.pos_to_string(p2))
+		meta:set_string("target", minetest.pos_to_string(target))
+	end
+	end
+	print("[nether] construction accepted.")
+	return true
+end
+
+-- destroy the portal when destroying obsidian
+minetest.override_item("default:obsidian", {
+	on_destruct = function(pos)
+		local meta = minetest.get_meta(pos)
+		local p1 = minetest.string_to_pos(meta:get_string("p1"))
+		local p2 = minetest.string_to_pos(meta:get_string("p2"))
+		local target = minetest.string_to_pos(meta:get_string("target"))
+		if not p1 or not p2 then
+			return
+		end
+		for x=p1.x,p2.x do
+		for y=p1.y,p2.y do
+		for z=p1.z,p2.z do
+			local nn = minetest.get_node({x=x,y=y,z=z}).name
+			if nn == "default:obsidian" or nn == "nether:portal" then
+				if nn == "nether:portal" then
+					minetest.remove_node({x=x,y=y,z=z})
+				end
+				local m = minetest.get_meta({x=x,y=y,z=z})
+				m:set_string("p1", "")
+				m:set_string("p2", "")
+				m:set_string("target", "")
+			end
+		end
+		end
+		end
+		meta = minetest.get_meta(target)
+		if not meta then
+			return
+		end
+		p1 = minetest.string_to_pos(meta:get_string("p1"))
+		p2 = minetest.string_to_pos(meta:get_string("p2"))
+		if not p1 or not p2 then
+			return
+		end
+		for x=p1.x,p2.x do
+		for y=p1.y,p2.y do
+		for z=p1.z,p2.z do
+			local nn = minetest.get_node({x=x,y=y,z=z}).name
+			if nn == "default:obsidian" or nn == "nether:portal" then
+				if nn == "nether:portal" then
+					minetest.remove_node({x=x,y=y,z=z})
+				end
+				local m = minetest.get_meta({x=x,y=y,z=z})
+				m:set_string("p1", "")
+				m:set_string("p2", "")
+				m:set_string("target", "")
+			end
+		end
+		end
+		end
+	end
+})
+
+-- override mese crystal fragment for making an obsidian portal
+minetest.after(0.1, function()
+	minetest.override_item("default:mese_crystal_fragment", {
+		on_place = function(stack, player, pt)
+			if pt.under
+			and minetest.get_node(pt.under).name == "default:obsidian" then
+				local done = make_portal(pt.under)
+				if done then
+					local pname = player:get_player_name()
+					minetest.chat_send_player(pname,
+						"Warning: If you are in the nether you may not be " ..
+						"able to find the way out!")
+					if not minetest.is_creative_enabled(pname) then
+						stack:take_item()
+					end
+				end
+			end
+			return stack
+		end
+	})
+end)
+
+
+-- a not filled square
+local function vector_square(r)
+	local tab, n = {}, 1
+	for i = -r+1, r do
+		for j = -1, 1, 2 do
+			local a, b = r*j, i*j
+			tab[n] = {a, b}
+			tab[n+1] = {b, a}
+			n=n+2
+		end
+	end
+	return tab
+end
+
+local function is_netherportal(pos)
+	local x, y, z = pos.x, pos.y, pos.z
+	for _,i in pairs({-1, 3}) do
+		if minetest.get_node({x=x, y=y+i, z=z}).name ~= "nether:white" then
+			return
+		end
+	end
+	for _,sn in pairs(vector_square(1)) do
+		if minetest.get_node({x=x+sn[1], y=y-1, z=z+sn[2]}).name ~= "nether:netherrack"
+		or minetest.get_node({x=x+sn[1], y=y+3, z=z+sn[2]}).name ~= "nether:blood_cooked" then
+			return
+		end
+	end
+	for _,sn in pairs(vector_square(2)) do
+		if minetest.get_node({x=x+sn[1], y=y-1, z=z+sn[2]}).name ~= "nether:netherrack_black"
+		or minetest.get_node({x=x+sn[1], y=y+3, z=z+sn[2]}).name ~= "nether:wood_empty" then
+			return
+		end
+	end
+	for i = -1,1,2 do
+		for j = -1,1,2 do
+			if minetest.get_node({x=x+i, y=y+2, z=z+j}).name ~= "nether:apple" then
+				return
+			end
+		end
+	end
+	for i = -2,2,4 do
+		for j = 0,2 do
+			for k = -2,2,4 do
+				if minetest.get_node({x=x+i, y=y+j, z=z+k}).name ~= "nether:netherrack_brick_blue" then
+					return
+				end
+			end
+		end
+	end
+	for i = -1,1 do
+		for j = -1,1 do
+			if minetest.get_node({x=x+i, y=y+4, z=z+j}).name ~= "nether:wood_empty" then
+				return
+			end
+		end
+	end
+	return true
+end
+
+-- cache known portals
+local known_portals_d = {}
+local known_portals_u = {}
+local function get_portal(t, z,x)
+	return t[z] and t[z][x]
+end
+local function set_portal(t, z,x, y)
+	t[z] = t[z] or {}
+	t[z][x] = y
+end
+
+local function get_player_nodepos(player)
+	local pos = player:get_pos()
+	pos.y = pos.y + player:get_properties().collisionbox[2] + 0.5
+	return vector.round(pos)
+end
+
+-- used when a player eats that fruit in a portal
+function nether.teleport_player(player)
+	if not player then
+		minetest.log("error", "[nether] Missing player.")
+		return
+	end
+	local pos = get_player_nodepos(player)
+	if not is_netherportal(pos) then
+		return
+	end
+	minetest.sound_play("nether_teleporter", {pos=pos})
+	local meta = minetest.get_meta({x=pos.x, y=pos.y-1, z=pos.z})
+	if pos.y < nether.start then
+		set_portal(known_portals_d, pos.z,pos.x, pos.y)
+
+		local my = tonumber(meta:get_string("y"))
+		local y = get_portal(known_portals_u, pos.z,pos.x)
+		if y then
+			if y ~= my then
+				meta:set_string("y", y)
+			end
+		else
+			y = my or 100
+		end
+		pos.y = y - 0.3
+
+		player_from_nether(player, pos)
+	else
+		set_portal(known_portals_u, pos.z,pos.x, pos.y)
+
+		local my = tonumber(meta:get_string("y"))
+		local y = get_portal(known_portals_d, pos.z,pos.x)
+		if y then
+			if y ~= my then
+				meta:set_string("y", y)
+			end
+		else
+			y = my or portal_target+math.random(4)
+		end
+		pos.y = y - 0.3
+
+		player_to_nether(player, pos)
+	end
+	minetest.sound_play("nether_teleporter", {pos=pos})
+	return true
+end

mods/nether/nether/settings.lua

@@ -0,0 +1,24 @@
+local default_settings = {
+	trap_players = true,
+	log_to_chat = false,
+	log_level = 2,
+	overworld_help = true,
+}
+
+nether.settings = {}
+
+for name,dv in pairs(default_settings) do
+	local setting
+	local setting_name = "nether." .. name
+	if type(dv) == "boolean" then
+		setting = minetest.settings:get_bool(setting_name)
+	elseif type(dv) == "number" then
+		setting = tonumber(minetest.settings:get(setting_name))
+	else
+		error"[nether] Only boolean and number settings are available"
+	end
+	if setting == nil then
+		setting = dv
+	end
+	nether[name] = setting
+end

mods/nether/nether/settingtypes.txt

@@ -0,0 +1,23 @@
+#    If enabled, regular players which are in the nether can leave it only with
+#    a nether portal and other ways of teleportation, e.g. the /spawn
+#    chatcommand, are blocked. Similarly, the nether can only be entered with a
+#    portal.
+#    This forces the players to investigate the nether and build a portal with
+#    hellish effort to go back to their home in the overworld.
+#    It is recommended to disable this setting in creative mode or if damage is
+#    disabled.
+nether.trap_players (Trap players) bool true
+
+#    If enabled, show log messages in the chat and not only in debug.txt
+nether.log_to_chat (Log messages to chat) bool false
+
+#    Specify how much text is printed for debugging purposes
+#    0: Disabled
+#    1: A bit of information
+#    2: Acceptable amount of information
+#    3: Lots of text
+nether.log_level (Log level) int 2 0 3
+
+#    If disabled, players cannot view the nether guide with /nether_help
+#    in the overworld.
+nether.overworld_help (Overworld help) bool true