try html formspec:

problems:
* image width and height doesn't seem to work
* font is too small

nether/guide.lua

@@ -315,6 +315,58 @@ local guide_forms = {
 }
 
 -- change the infos to formspecs
+for n,data in ipairs(guide_infos) do
+	local html_text = ""
+	local form = ""
+	local y = 0
+	local x = guide_size.cx
+	for _,i in ipairs(data) do
+		local typ, content = unpack(i)
+		if typ == "y" then
+			y = y+content
+		elseif typ == "x" then
+			x = math.max(x, content)
+		elseif typ == "text" then
+			html_text = html_text .. content .. "\n"
+			local tab = minetest.wrap_text(content, guide_size.fx, true)
+			local l = guide_size.cx
+			for _,str in ipairs(tab) do
+				--~ form = form.."label["..guide_size.cx ..","..guide_size.cy+y..";"..str.."]"
+				y = y+guide_size.fy
+				l = math.max(l, #str)
+			end
+			x = math.max(x, l/font_size)
+		elseif typ == "image" then
+			local w, h, texture_name, px, py = unpack(content)
+			if not px then
+				--~ form = form.."image["..guide_size.cx..","..guide_size.cy+y+h*0.3 ..";"..w..","..h..";"..texture_name.."]"
+				html_text = html_text ..
+					("<img name=%s width=%g height=%g>\n"):format(
+					texture_name, w, h)
+				y = y+h
+			else
+				px = guide_size.cx+px
+				py = py or 0
+				html_text = html_text ..
+					("<img name=%s width=%g height=%g>\n"):format(
+					texture_name, w, h)
+				--~ form = form.."image["..px..","..
+					--~ guide_size.cy+y+h*0.3+py ..";"..w..","..h..";"..texture_name.."]"
+				x = math.max(x, px+w)
+			end
+		end
+	end
+	form = ("formspec_version[4]size[%g,%g;]hypertext[0,0;%g,%g;html;%s]button[%g,%g;1,2;quit;Back]"
+		):format(
+		x * 1.8, y + 1,
+		x * 1.8, y,
+		minetest.formspec_escape(html_text),
+		0.5 * x - 0.5, y)
+
+	guide_forms[n] = {data.description, form}
+end
+print(dump(guide_forms))
+--[[
 for n,data in ipairs(guide_infos) do
 	local form = ""
 	local y = 0
@@ -351,6 +403,7 @@ for n,data in ipairs(guide_infos) do
 	form = "size["..x*1.8 ..","..y+1 ..";]"..form.."button["..x/2-0.5 ..","..y ..";1,2;quit;Back]"
 	guide_forms[n] = {data.description, form}
 end
+--]]
 
 local desc_tab = {}
 for n,i in ipairs(guide_forms) do

nether/init.lua

@@ -19,15 +19,6 @@ end
 
 --== EDITABLE OPTIONS ==--
 
---says some information.
-nether.info = true
-
--- tell everyone about the generation
-nether.inform_all = minetest.is_singleplayer()
-
---1:<a bit of information> 2:<acceptable amount of information> 3:<lots of text>
-nether.max_spam = 2
-
 -- Depth of the nether
 local nether_middle = -20000
 
@@ -94,9 +85,17 @@ local NETHER_SHROOM_FREQ = 100
 
 --== END OF EDITABLE OPTIONS ==--
 
-if nether.info then
+local path = minetest.get_modpath"nether"
+dofile(path .. "/settings.lua")
+local nether_weird_noise = dofile(path .. "/weird_mapgen_noise.lua")
+dofile(path .. "/items.lua")
+--dofile(path .. "/furnace.lua")
+dofile(path .. "/pearl.lua")
+
+
+if nether.log_level >= 1 then
 	function nether:inform(msg, spam, t)
-		if spam <= self.max_spam then
+		if spam <= self.log_level then
 			local info
 			if t then
 				info = "[nether] " .. msg .. (" after ca. %.3g s"):format(
@@ -105,7 +104,7 @@ if nether.info then
 				info = "[nether] " .. msg
 			end
 			print(info)
-			if self.inform_all then
+			if self.log_to_chat then
 				minetest.chat_send_all(info)
 			end
 		end
@@ -116,12 +115,6 @@ else
 end
 
 
-local path = minetest.get_modpath"nether"
-local nether_weird_noise = dofile(path.."/weird_mapgen_noise.lua")
-dofile(path.."/items.lua")
---dofile(path.."/furnace.lua")
-dofile(path.."/pearl.lua")
-
 -- Weierstrass function stuff from https://github.com/slemonide/gen
 local SIZE = 1000
 local ssize = math.ceil(math.abs(SIZE))

nether/portal.lua

@@ -2,8 +2,7 @@
 
 -- kills the player if he uses PilzAdam portal
 local portal_target = nether.buildings+1
-local nether_prisons = minetest.settings:get_bool("enable_damage")
-local obsidian_portal_kills = nether_prisons and true
+local damage_enabled = minetest.settings:get_bool"enable_damage"
 local mclike_portal = false
 
 local abm_allowed
@@ -13,21 +12,21 @@ end)
 
 local save_path = minetest.get_worldpath() .. "/nether_players"
 local players_in_nether = {}
--- only get info from file if nether prisons
-if nether_prisons then
+
+-- 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 not file then
-		return
-	end
+	if file then
 		local contents = file:read"*all"
 		io.close(file)
-	if not contents then
-		return
-	end
+		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()
@@ -43,7 +42,7 @@ local function save_nether_players()
 end
 
 local update_background
-if nether_prisons then
+if nether.trap_players then
 	function update_background(player, down)
 		if down then
 			player:set_sky({r=15, g=0, b=0}, "plain")
@@ -95,9 +94,6 @@ end
 -- teleports players to nether or helps it
 local function player_to_nether(player, pos)
 	local pname = player:get_player_name()
-	if players_in_nether[pname] then
-		return
-	end
 	players_in_nether[pname] = true
 	save_nether_players()
 	update_background(player, true)
@@ -107,8 +103,10 @@ local function player_to_nether(player, pos)
 	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)
-	if not nether_prisons then
+	end
+	if not damage_enabled or not nether.trap_players then
 		player:set_pos(get_player_died_target(player))
 	end
 end
@@ -119,7 +117,7 @@ local function player_from_nether(player, pos)
 		players_in_nether[pname] = nil
 		save_nether_players()
 	end
-	update_background(player)
+	update_background(player, false)
 	player:set_pos(pos)
 end
 
@@ -179,7 +177,8 @@ minetest.register_chatcommand("from_hell", {
 })
 
 
-if nether_prisons then
+-- 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()
@@ -229,7 +228,7 @@ if nether_prisons then
 			else
 				minetest.log("action", "Player \"" .. pname ..
 					"\" must not be in the nether, teleporting it!")
-				update_background(player)
+				update_background(player, false)
 				current_pos.y = 20
 				player:set_pos(current_pos)
 			end
@@ -266,12 +265,6 @@ if nether_prisons then
 			end
 		end
 	end)
-else
-	-- test if player is in nether when he/she joins
-	minetest.register_on_joinplayer(function(player)
-		players_in_nether[player:get_player_name()] =
-			player:get_pos().y < nether.start or nil
-	end)
 end
 
 -- removes the violet stuff from the obsidian portal
@@ -317,7 +310,7 @@ local function obsi_teleport_player(player, pos, target)
 	end
 
 	local has_teleported
-	if obsidian_portal_kills then
+	if damage_enabled then
 		obsidian_teleport(player, pname)
 		has_teleported = true
 	elseif not mclike_portal then
@@ -649,13 +642,19 @@ local function set_portal(t, z,x, y)
 	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 = vector.round(player:get_pos())
+	local pos = get_player_nodepos(player)
 	if not is_netherportal(pos) then
 		return
 	end

nether/settings.lua

@@ -0,0 +1,23 @@
+local default_settings = {
+	trap_players = true,
+	log_to_chat = false,
+	log_level = 2,
+}
+
+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

nether/settingtypes.txt

@@ -0,0 +1,19 @@
+#    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