diff --git a/README.txt b/README.txt
index 8d99a52..a3a52e7 100644
--- a/README.txt
+++ b/README.txt
@@ -1,4 +1,4 @@
-watershed 0.3.0 by paramat
+watershed 0.3.1 by paramat
 For latest stable Minetest back to 0.4.8
 Depends default
 Licenses: code WTFPL
\ No newline at end of file
diff --git a/functions.lua b/functions.lua
index 0a6863d..56af3f2 100644
--- a/functions.lua
+++ b/functions.lua
@@ -249,137 +249,143 @@ minetest.register_abm({
 	end,
 })
 
--- Set mapgen parameters
+-- Singlenode mapgen option
 
-minetest.register_on_mapgen_init(function(mgparams)
-	minetest.set_mapgen_params({mgname="singlenode", flags = "nolight", flagmask = "nolight"})
-end)
+local SINGLENODE = true
 
--- Spawn player
+if SINGLENODE then
+	-- Set mapgen parameters
 
-function spawnplayer(player)
-	local TERCEN = -160 -- Terrain 'centre', average seabed level
-	local TERSCA = 512 -- Vertical terrain scale
-	local ATANAMP = 1.1 -- Arctan function amplitude, smaller = more and larger floatlands above ridges
-	local XLSAMP = 0.2 -- Extra large scale height variation amplitude
-	local BASAMP = 0.4 -- Base terrain amplitude
-	local CANAMP = 0.4 -- Canyon terrain amplitude
-	local CANEXP = 1.33 -- Canyon shape exponent
-	local xsp
-	local ysp
-	local zsp
-	local np_rough = {
-		offset = 0,
-		scale = 1,
-		spread = {x=512, y=512, z=512},
-		seed = 593,
-		octaves = 6,
-		persist = 0.63
-	}
-	local np_smooth = {
-		offset = 0,
-		scale = 1,
-		spread = {x=512, y=512, z=512},
-		seed = 593,
-		octaves = 6,
-		persist = 0.3
-	}
-	local np_fault = {
-		offset = 0,
-		scale = 1,
-		spread = {x=512, y=1024, z=512},
-		seed = 14440002,
-		octaves = 6,
-		persist = 0.5
-	}
-	local np_base = {
-		offset = 0,
-		scale = 1,
-		spread = {x=4096, y=4096, z=4096},
-		seed = 8890,
-		octaves = 4,
-		persist = 0.4
-	}
-	local np_xlscale = {
-		offset = 0,
-		scale = 1,
-		spread = {x=8192, y=8192, z=8192},
-		seed = -72,
-		octaves = 3,
-		persist = 0.4
-	}
-	for chunk = 1, 32 do
-		print ("[watershed] chunk "..chunk)
-		local x0 = 80 * math.random(-24, 24) - 32
-		local z0 = 80 * math.random(-24, 24) - 32
-		local y0 = -32
-		local x1 = x0 + 79
-		local z1 = z0 + 79
-		local y1 = 47
+	minetest.register_on_mapgen_init(function(mgparams)
+		minetest.set_mapgen_params({mgname="singlenode", flags = "nolight", flagmask = "nolight"})
+	end)
+
+	-- Spawn player
+
+	function spawnplayer(player)
+		local TERCEN = -160 -- Terrain 'centre', average seabed level
+		local TERSCA = 512 -- Vertical terrain scale
+		local ATANAMP = 1.1 -- Arctan function amplitude, smaller = more and larger floatlands above ridges
+		local XLSAMP = 0.2 -- Extra large scale height variation amplitude
+		local BASAMP = 0.4 -- Base terrain amplitude
+		local CANAMP = 0.4 -- Canyon terrain amplitude
+		local CANEXP = 1.33 -- Canyon shape exponent
+		local xsp
+		local ysp
+		local zsp
+		local np_rough = {
+			offset = 0,
+			scale = 1,
+			spread = {x=512, y=512, z=512},
+			seed = 593,
+			octaves = 6,
+			persist = 0.63
+		}
+		local np_smooth = {
+			offset = 0,
+			scale = 1,
+			spread = {x=512, y=512, z=512},
+			seed = 593,
+			octaves = 6,
+			persist = 0.3
+		}
+		local np_fault = {
+			offset = 0,
+			scale = 1,
+			spread = {x=512, y=1024, z=512},
+			seed = 14440002,
+			octaves = 6,
+			persist = 0.5
+		}
+		local np_base = {
+			offset = 0,
+			scale = 1,
+			spread = {x=4096, y=4096, z=4096},
+			seed = 8890,
+			octaves = 4,
+			persist = 0.4
+		}
+		local np_xlscale = {
+			offset = 0,
+			scale = 1,
+			spread = {x=8192, y=8192, z=8192},
+			seed = -72,
+			octaves = 3,
+			persist = 0.4
+		}
+		for chunk = 1, 32 do
+			print ("[watershed] chunk "..chunk)
+			local x0 = 80 * math.random(-24, 24) - 32
+			local z0 = 80 * math.random(-24, 24) - 32
+			local y0 = -32
+			local x1 = x0 + 79
+			local z1 = z0 + 79
+			local y1 = 47
 		
-		local sidelen = 80
-		local chulens = {x=sidelen, y=sidelen, z=sidelen}
-		local minposxyz = {x=x0, y=y0, z=z0}
-		local minposxz = {x=x0, y=z0}
+			local sidelen = 80
+			local chulens = {x=sidelen, y=sidelen, z=sidelen}
+			local minposxyz = {x=x0, y=y0, z=z0}
+			local minposxz = {x=x0, y=z0}
 	
-		local nvals_rough = minetest.get_perlin_map(np_rough, chulens):get3dMap_flat(minposxyz)
-		local nvals_smooth = minetest.get_perlin_map(np_smooth, chulens):get3dMap_flat(minposxyz)
-		local nvals_fault = minetest.get_perlin_map(np_fault, chulens):get3dMap_flat(minposxyz)
+			local nvals_rough = minetest.get_perlin_map(np_rough, chulens):get3dMap_flat(minposxyz)
+			local nvals_smooth = minetest.get_perlin_map(np_smooth, chulens):get3dMap_flat(minposxyz)
+			local nvals_fault = minetest.get_perlin_map(np_fault, chulens):get3dMap_flat(minposxyz)
 	
-		local nvals_base = minetest.get_perlin_map(np_base, chulens):get2dMap_flat(minposxz)
-		local nvals_xlscale = minetest.get_perlin_map(np_xlscale, chulens):get2dMap_flat(minposxz)
+			local nvals_base = minetest.get_perlin_map(np_base, chulens):get2dMap_flat(minposxz)
+			local nvals_xlscale = minetest.get_perlin_map(np_xlscale, chulens):get2dMap_flat(minposxz)
 		
-		local nixz = 1
-		local nixyz = 1
-		for z = z0, z1 do
-			for y = y0, y1 do
-				for x = x0, x1 do
-					local grad = math.atan((TERCEN - y) / TERSCA) * ATANAMP
-					local n_base = nvals_base[nixz]
-					local terblen = math.max(1 - math.abs(n_base), 0)
-					local densitybase = (1 - math.abs(n_base)) * BASAMP + nvals_xlscale[nixz] * XLSAMP + grad
-					local density
-					if nvals_fault[nixyz] >= 0 then
-						density = densitybase
-						+ math.abs(nvals_rough[nixyz] * terblen
-						+ nvals_smooth[nixyz] * (1 - terblen)) ^ CANEXP * CANAMP
-					else	
-						density = densitybase
-						+ math.abs(nvals_rough[nixyz] * terblen
-						- nvals_smooth[nixyz] * (1 - terblen)) ^ CANEXP * CANAMP
+			local nixz = 1
+			local nixyz = 1
+			for z = z0, z1 do
+				for y = y0, y1 do
+					for x = x0, x1 do
+						local grad = math.atan((TERCEN - y) / TERSCA) * ATANAMP
+						local n_base = nvals_base[nixz]
+						local terblen = math.max(1 - math.abs(n_base), 0)
+						local densitybase = (1 - math.abs(n_base)) * BASAMP + nvals_xlscale[nixz] * XLSAMP + grad
+						local density
+						if nvals_fault[nixyz] >= 0 then
+							density = densitybase
+							+ math.abs(nvals_rough[nixyz] * terblen
+							+ nvals_smooth[nixyz] * (1 - terblen)) ^ CANEXP * CANAMP
+						else	
+							density = densitybase
+							+ math.abs(nvals_rough[nixyz] * terblen
+							- nvals_smooth[nixyz] * (1 - terblen)) ^ CANEXP * CANAMP
+						end
+						if y >= 1 and density > -0.01 and density < 0 then
+							ysp = y
+							xsp = x
+							zsp = z
+							break
+						end
+						nixz = nixz + 1
+						nixyz = nixyz + 1
 					end
-					if y >= 1 and density > -0.01 and density < 0 then
-						ysp = y
-						xsp = x
-						zsp = z
+					if ysp then
 						break
 					end
-					nixz = nixz + 1
-					nixyz = nixyz + 1
+					nixz = nixz - 80
 				end
 				if ysp then
 					break
 				end
-				nixz = nixz - 80
+				nixz = nixz + 80
 			end
 			if ysp then
 				break
 			end
-			nixz = nixz + 80
-		end
-		if ysp then
-			break
 		end
+		print ("[watershed] spawn player ("..xsp.." "..ysp.." "..zsp..")")
+		player:setpos({x=xsp, y=ysp, z=zsp})
 	end
-	print ("[watershed] spawn player ("..xsp.." "..ysp.." "..zsp..")")
-	player:setpos({x=xsp, y=ysp, z=zsp})
-end
 
-minetest.register_on_newplayer(function(player)
-	spawnplayer(player)
-end)
+	minetest.register_on_newplayer(function(player)
+		spawnplayer(player)
+	end)
 
-minetest.register_on_respawnplayer(function(player)
-	spawnplayer(player)
-	return true
-end)
\ No newline at end of file
+	minetest.register_on_respawnplayer(function(player)
+		spawnplayer(player)
+		return true
+	end)
+end
\ No newline at end of file
diff --git a/init.lua b/init.lua
index e40563e..6fa6def 100644
--- a/init.lua
+++ b/init.lua
@@ -1,11 +1,14 @@
--- watershed 0.3.0 by paramat
+-- watershed 0.3.1 by paramat
 -- For latest stable Minetest and back to 0.4.8
 -- Depends default
 -- License: code WTFPL
 
--- add snowy plains biome
+-- bugfixes
+-- optional mod clouds
+-- stacked realm / singlenode option
+-- volcanoes
 -- TODO
--- lava at surface: volcanic cone?
+-- check river continuous over faults
 -- tree heights vary
 -- fog
 
@@ -16,6 +19,7 @@ local YMAX = 33000 -- Approximate top of atmosphere / mountains / floatlands
 local TERCEN = -160 -- Terrain 'centre', average seabed level
 local YWAT = 1 -- Sea surface y
 local YCLOUD = 128 -- Cloud level
+local CLOUDS = false
 
 local TERSCA = 512 -- Vertical terrain scale
 local XLSAMP = 0.2 -- Extra large scale height variation amplitude
@@ -24,7 +28,7 @@ local CANAMP = 0.4 -- Canyon terrain amplitude
 local CANEXP = 1.33 -- Canyon shape exponent
 local ATANAMP = 1.1 -- Arctan function amplitude, smaller = more and larger floatlands above ridges
 
-local TSTONE = 0.01 -- Density threshold for stone, depth of soil at TERCEN
+local TSTONE = 0.02 -- Density threshold for stone, depth of soil at TERCEN
 local TRIV = -0.015 -- Maximum densitybase threshold for river water
 local TSAND = -0.018 -- Maximum densitybase threshold for river sand
 local TLAVA = 2 -- Maximum densitybase threshold for lava
@@ -34,16 +38,16 @@ local ORETHI = 0.001 -- Ore seam thickness tuner
 local ORET = 0.02 -- Ore threshold for seam
 local TCLOUD = 0.5 -- Cloud threshold
 
-local HITET = 0.4 -- High temperature threshold
-local LOTET = -0.4 -- Low ..
-local ICETET = -0.8 -- Ice ..
-local HIHUT = 0.4 -- High humidity threshold
-local LOHUT = -0.4 -- Low ..
+local HITET = 0.35 -- High temperature threshold
+local LOTET = -0.35 -- Low ..
+local ICETET = -0.7 -- Ice ..
+local HIHUT = 0.35 -- High humidity threshold
+local LOHUT = -0.35 -- Low ..
 local CLOHUT = 0 -- Cloud humidity threshold
 local DCLOHUT = 1 -- Dark cloud ..
 
-local PINCHA = 47 -- Pine tree 1/x chance per node
-local APTCHA = 47 -- Appletree
+local PINCHA = 49 -- Pine tree 1/x chance per node
+local APTCHA = 49 -- Appletree
 local FLOCHA = 36 -- Flower
 local FOGCHA = 9 -- Forest grass
 local GRACHA = 3 -- Grassland grasses
@@ -52,7 +56,7 @@ local JUGCHA = 9 -- Junglegrass
 local CACCHA = 841 -- Cactus
 local DRYCHA = 169 -- Dry shrub
 local PAPCHA = 3 -- Papyrus
-local ACACHA = 841 -- Acacia tree
+local ACACHA = 529 -- Acacia tree
 local GOGCHA = 3 -- Golden grass
 
 -- 3D noise for rough terrain
@@ -183,7 +187,7 @@ local np_magma = {
 	scale = 1,
 	spread = {x=128, y=128, z=128},
 	seed = -13,
-	octaves = 1,
+	octaves = 2,
 	persist = 0.5
 }
 
@@ -264,6 +268,7 @@ minetest.register_on_generated(function(minp, maxp, seed)
 	local c_gravel = minetest.get_content_id("default:gravel")
 	local c_clay = minetest.get_content_id("default:clay")
 	local c_grass5 = minetest.get_content_id("default:grass_5")
+	local c_obsidian = minetest.get_content_id("default:obsidian")
 	
 	local c_wswater = minetest.get_content_id("watershed:water")
 	local c_wsstone = minetest.get_content_id("watershed:stone")
@@ -316,10 +321,10 @@ minetest.register_on_generated(function(minp, maxp, seed)
 				local terblen = math.max(1 - math.abs(n_base), 0)
 				local densitybase = (1 - math.abs(n_base)) * BASAMP + nvals_xlscale[nixz] * XLSAMP + grad
 				local altprop = (y - YWAT) / (TERCEN + TERSCA - YWAT)
-				local triv = TRIV * (1 - altprop * 1.1)
-				local tsand = TSAND * (1 - altprop * 1.1)
+				local triv = TRIV * (1 - terblen)
+				local tsand = TSAND * (1 - terblen * 1.1)
 				local tstone = TSTONE * (1 - math.atan(altprop) * 0.6) -- 1 to 0.05
-				local tlava = TLAVA * (0.9 - nvals_magma[nixz] ^ 4 * terblen ^ 16)
+				local tlava = TLAVA * (1 - nvals_magma[nixz] ^ 4 * terblen ^ 16)
 				local density
 				if nvals_fault[nixyz] >= 0 then
 					density = densitybase
@@ -389,10 +394,16 @@ minetest.register_on_generated(function(minp, maxp, seed)
 						end
 					end
 				
-					if density >= tstone and densitybase >= tlava then
-						data[vi] = c_wslava
+					if densitybase >= tlava then
+						if densitybase >= -0.05 then
+							data[vi] = c_wslava
+						end
 						stable[si] = 0
 						under[si] = 0
+					elseif densitybase >= tlava - 0.5 and densitybase >= -0.1 then
+						data[vi] = c_obsidian
+						stable[si] = 1
+						under[si] = 0
 					elseif density >= tstone and nofis  -- stone cut by fissures
 					or (density >= tstone and density < TSTONE * 3 and y <= YWAT) -- stone around water
 					or (density >= tstone and density < TSTONE * 3 and densitybase >= triv ) then -- stone around river
@@ -495,7 +506,7 @@ minetest.register_on_generated(function(minp, maxp, seed)
 						end
 						stable[si] = 0
 						under[si] = 0
-					elseif y == YCLOUD then -- clouds
+					elseif CLOUDS and y == YCLOUD then -- clouds
 						local xrq = 16 * math.floor((x - x0) / 16) -- quantise to 16x16 lattice
 						local zrq = 16 * math.floor((z - z0) / 16)
 						local qixz = zrq * 80 + xrq + 1 -- quantised index
@@ -604,16 +615,18 @@ minetest.register_on_generated(function(minp, maxp, seed)
 							end
 						elseif under[si] == 2 then
 							data[viu] = c_dirtsnow
+						elseif under[si] == 3 then
+							data[viu] = c_dirtsnow
+						elseif under[si] == 4 then
+							data[viu] = c_wsdrygrass
 						elseif under[si] == 5 then
 							data[viu] = c_wsgrass
-						elseif under[si] == 3 then
-							data[viu] = c_wsdrygrass
-						elseif under[si] == 4 then
+						elseif under[si] == 6 then
 							data[viu] = c_wsgrass
 						elseif under[si] == 8 then
-							data[viu] = c_wsgrass
-						elseif under[si] == 7 then
 							data[viu] = c_wsdrygrass
+						elseif under[si] == 9 then
+							data[viu] = c_wsgrass
 						end
 					end
 				end
diff --git a/nodes.lua b/nodes.lua
index 73642e0..df73879 100644
--- a/nodes.lua
+++ b/nodes.lua
@@ -274,7 +274,7 @@ minetest.register_node("watershed:lava", {
 	liquid_alternative_source = "watershed:lava",
 	liquid_viscosity = LAVA_VISC,
 	liquid_renewable = false,
-	liquid_range = 2,
+	liquid_range = 0,
 	damage_per_second = 8,
 	post_effect_color = {a=192, r=255, g=64, b=0},
 	groups = {lava=3, liquid=2, hot=3, igniter=1},
@@ -313,7 +313,7 @@ minetest.register_node("watershed:lavaflow", {
 	liquid_alternative_source = "watershed:lava",
 	liquid_viscosity = LAVA_VISC,
 	liquid_renewable = false,
-	liquid_range = 2,
+	liquid_range = 0,
 	damage_per_second = 8,
 	post_effect_color = {a=192, r=255, g=64, b=0},
 	groups = {lava=3, liquid=2, hot=3, igniter=1, not_in_creative_inventory=1},