diff --git a/controller.lua b/controller.lua
index 36c9ad2..ffda5dc 100644
--- a/controller.lua
+++ b/controller.lua
@@ -51,7 +51,7 @@ local get_controller_assembled_formspec = function(digtron_id, player_name)
 			.. "position[0.025,0.1]"
 			.. "anchor[0,0]"
 			.. "container[0,0]"
-			.. "list[detached:" .. digtron_id .. ";"..inv_list..";0,0;8,4]" -- TODO: paging system for inventory
+			.. "list[detached:" .. digtron_id .. ";"..inv_list..";0,0;8,5]" -- TODO: paging system for inventory
 			.. "container_end[]"
 			.. "container[0,5]list[current_player;main;0,0;8,1;]list[current_player;main;0,1.25;8,3;8]container_end[]"
 			.. "listring[current_player;main]"
@@ -64,10 +64,10 @@ local get_controller_assembled_formspec = function(digtron_id, player_name)
 		.. "container[0,0]"
 		.. "button[0,0;1,1;disassemble;Disassemble]"
 		.. "field[1.2,0.3;1.75,1;digtron_name;Digtron name;"
-		..minetest.formspec_escape(digtron.get_name(digtron_id)).."]"
+		.. minetest.formspec_escape(digtron.get_name(digtron_id)).."]"
 		.. "field_close_on_enter[digtron_name;false]"
 		.. "field[2.9,0.3;0.7,1;cycles;Cycles;1]" -- TODO persist, actually use
-		.. "button[3.2,0;1,1;test_dig;Execute]"
+		.. "button[3.2,0;1,1;execute;Execute]"
 		.. "container_end[]"
 		
 		.. "container[0,1]"
@@ -82,7 +82,7 @@ local get_controller_assembled_formspec = function(digtron_id, player_name)
 		.. "container_end[]"
 
 		.. "container[0.5,3.2]"
-		.. "box[0,0;3,2;#CCCCCC]"
+		.. "box[0,0;3,2;#DDDDDD]"
 		.. "label[1.3,0.825;Rotate]"
 		.. "button[0.1,0.1;1,1;rot_counterclockwise;Widdershins]"
 		.. "button[2.1,0.1;1,1;rot_clockwise;Clockwise]"
@@ -174,7 +174,7 @@ minetest.register_on_player_receive_fields(function(player, formname, fields)
 		digtron.rotate(digtron_id, digtron.facedir_to_up(facedir), player_name)
 	end
 
-	if fields.test_dig then
+	if fields.execute then
 		digtron.execute_cycle(digtron_id, player_name)
 	end
 	
@@ -195,7 +195,19 @@ minetest.register_on_player_receive_fields(function(player, formname, fields)
 	end	
 end)
 
-minetest.register_node("digtron:controller", {
+-- Doesn't deep-copy
+local combine_defs = function(base_def, override_content)
+	local out = {}
+	for key, value in pairs(base_def) do
+		out[key] = value
+	end
+	for key, value in pairs(override_content) do
+		out[key] = value
+	end
+	return out
+end
+
+local base_def = {
 	description = S("Digtron Control Module"),
 	_doc_items_longdesc = nil,
     _doc_items_usagehelp = nil,
@@ -231,6 +243,46 @@ minetest.register_node("digtron:controller", {
 		},
 	},
 	sounds = default.node_sound_metal_defaults(),
+	on_blast = digtron.on_blast,
+}
+
+minetest.register_node("digtron:controller_unassembled", combine_defs(base_def, {
+	_digtron_assembled_node = "digtron:controller",
+
+	on_rightclick = function(pos, node, clicker, itemstack, pointed_thing)
+		local returnstack, success = digtron.on_rightclick(pos, node, clicker, itemstack, pointed_thing)
+		if returnstack then
+			return returnstack, success
+		end
+
+		if clicker == nil then return end
+		
+		local player_name = clicker:get_player_name()
+		local digtron_id = digtron.assemble(pos, player_name)
+		if digtron_id then
+			local meta = minetest.get_meta(pos)
+			meta:set_string("digtron_id", digtron_id)
+			meta:mark_as_private("digtron_id")
+			player_interacting_with_digtron_id[player_name] = {digtron_id = digtron_id}
+			minetest.show_formspec(player_name,
+				"digtron:controller_assembled",
+				get_controller_assembled_formspec(digtron_id, player_name))
+		end
+	end
+}))
+
+minetest.register_node("digtron:controller", combine_defs(base_def, {
+
+	tiles = {
+		"digtron_plate.png^[transformR90",
+		"digtron_plate.png^[transformR270",
+		"digtron_plate.png",
+		"digtron_plate.png^[transformR180",
+		"digtron_plate.png",
+		"digtron_plate.png^digtron_control.png^digtron_intermittent.png",
+	},
+	_digtron_disassembled_node = "digtron:controller_unassembled",
+	groups = {cracky = 3, oddly_breakable_by_hand = 3, not_in_creative_inventory = 1},
 	
 	on_dig = function(pos, node, digger)
 		local player_name
@@ -249,7 +301,7 @@ minetest.register_node("digtron:controller", {
 		if stack:get_count() > 0 then
 			minetest.add_item(pos, stack)
 		end		
-		-- call on_dignodes callback
+		-- TODO call on_dignodes callback
 		if digtron_id ~= "" then
 			local removed = digtron.remove_from_world(digtron_id, player_name)
 			for _, removed_pos in ipairs(removed) do
@@ -280,11 +332,6 @@ minetest.register_node("digtron:controller", {
 		local stack_meta = itemstack:get_meta()
 		local digtron_id = stack_meta:get_string("digtron_id")
 		if digtron_id ~= "" then
-			-- Test if Digtron will fit the surroundings
-			-- if not, try moving it up so that the lowest y-coordinate on the Digtron is
-			-- at the y-coordinate of the place clicked on and test again.
-			-- if that fails, show ghost of Digtron and fail to place.
-			
 			local target_pos
 			local below_node = minetest.get_node(pointed_thing.under)
 			local below_def = minetest.registered_nodes[below_node.name]
@@ -293,23 +340,36 @@ minetest.register_node("digtron:controller", {
 			else
 				target_pos = pointed_thing.above
 			end
+			-- TODO rotate layout based on player orientation
+			
+			-- move up so that the lowest y-coordinate on the Digtron is
+			-- at the y-coordinate of the place clicked on and test again.
+			local bbox = digtron.get_bounding_box(digtron_id)
+			target_pos.y = target_pos.y + math.abs(bbox.minp.y)
 
 			if target_pos then
 				local success, succeeded, failed = digtron.is_buildable_to(digtron_id, nil, target_pos, player_name)
 				if success then
-					digtron.build_to_world(digtron_id, nil, target_pos, player_name)
+					local built_positions = digtron.build_to_world(digtron_id, nil, target_pos, player_name)
+					for _, built_pos in ipairs(built_positions) do
+						minetest.check_for_falling(built_pos)
+					end
+
 					minetest.sound_play("digtron_machine_assemble", {gain = 0.5, pos=target_pos})
 					-- Note: DO NOT RESPECT CREATIVE MODE here.
 					-- If we allow multiple copies of a Digtron running around with the same digtron_id,
 					-- human sacrifice, dogs and cats living together, mass hysteria
 					return ItemStack("")
 				else
+					-- if that fails, show ghost of Digtron and fail to place.
 					digtron.show_buildable_nodes(succeeded, failed)
 					minetest.sound_play("digtron_buzzer", {gain = 0.5, pos=target_pos})
 				end
 			end
 			return itemstack
 		else
+			-- Should be impossible to have a controller without an ID, but if it happens place an unassembled node
+			itemstack:set_name("digtron:controller_unassembled")
 			return minetest.item_place(itemstack, placer, pointed_thing)
 		end
 	end,
@@ -336,29 +396,15 @@ minetest.register_node("digtron:controller", {
 		
 		local meta = minetest.get_meta(pos)
 		local digtron_id = meta:get_string("digtron_id")
-		local player_name = clicker:get_player_name()
 		
 		if digtron_id == "" then
-			local digtron_id = digtron.assemble(pos, player_name)
-			if digtron_id then
-				meta:set_string("digtron_id", digtron_id)
-				meta:mark_as_private("digtron_id")
-				player_interacting_with_digtron_id[player_name] = {digtron_id = digtron_id}
-				minetest.show_formspec(player_name,
-					"digtron:controller_assembled",
-					get_controller_assembled_formspec(digtron_id, player_name))
-			end
+			-- TODO: error message, fix digtron
 		else
-			-- initialized
+			local player_name = clicker:get_player_name()
 			player_interacting_with_digtron_id[player_name] = {digtron_id = digtron_id}
 			minetest.show_formspec(player_name,
 				"digtron:controller_assembled",
 				get_controller_assembled_formspec(digtron_id, player_name))
 		end
 	end,
-	
-	on_timer = function(pos, elapsed)
-	end,
-	
-	on_blast = digtron.on_blast,
-})
\ No newline at end of file
+}))
\ No newline at end of file
diff --git a/functions.lua b/functions.lua
index 4a1fa06..690c710 100644
--- a/functions.lua
+++ b/functions.lua
@@ -24,8 +24,6 @@ local get_predictive_inventory = inventory_functions.get_predictive_inventory
 local commit_predictive_inventory = inventory_functions.commit_predictive_inventory
 local clear_predictive_inventory = inventory_functions.clear_predictive_inventory
 
-digtron.retrieve_inventory = retrieve_inventory -- used by formspecs
-
 --------------------------------------------------------------------------------------
 
 local create_new_id = function()
@@ -58,11 +56,11 @@ end
 -- Name
 
 -- Not bothering with a dynamic table store for names, they're just strings with no need for serialization or deserialization
-digtron.get_name = function(digtron_id)
+local get_name = function(digtron_id)
 	return mod_meta:get_string(digtron_id..":name")
 end
 
-digtron.set_name = function(digtron_id, digtron_name)
+local set_name = function(digtron_id, digtron_name)
 	-- Don't allow a name to be set for a non-existent Digtron
 	if mod_meta:get(digtron_id..":layout") then
 		mod_meta:set_string(digtron_id..":name", digtron_name)
@@ -109,8 +107,6 @@ end
 local persist_layout, retrieve_layout = get_table_functions("layout")
 local persist_pos, retrieve_pos, dispose_pos = get_table_functions("pos")
 
-digtron.get_pos = retrieve_pos
-
 -------------------------------------------------------------------------------------------------------
 -- Layout creation helpers
 
@@ -253,15 +249,9 @@ table.insert(dispose_callbacks, invalidate_layout_cache)
 -- assemble and disassemble
 
 -- Returns the id of the new Digtron record, or nil on failure
-digtron.assemble = function(root_pos, player_name)
-	local node = minetest.get_node(root_pos)
-	-- TODO: a more generic test? Not needed with the more generic controller design, as far as I can tell. There's only going to be the one type of controller.
-	if node.name ~= "digtron:controller" then
-		-- Called on an incorrect node
-		minetest.log("error", "[Digtron] digtron.assemble called with pos " .. minetest.pos_to_string(root_pos)
-			.. " but the node at this location was " .. node.name)
-		return nil
-	end
+local assemble = function(root_pos, player_name)
+	local root_node = minetest.get_node(root_pos)
+		
 	local root_meta = minetest.get_meta(root_pos)
 	if root_meta:contains("digtron_id") then
 		-- Already assembled. TODO: validate that the digtron_id actually exists as well
@@ -269,8 +259,18 @@ digtron.assemble = function(root_pos, player_name)
 			.. " but the controller at this location was already part of a assembled Digtron.")
 		return nil
 	end
+	local digtron_name = root_meta:get_string("infotext")
+	
+	-- This should be called on an unassembled node.
+	if root_node.name ~= "digtron:controller_unassembled" then
+		-- Called on an incorrect node
+		minetest.log("error", "[Digtron] digtron.assemble called with pos " .. minetest.pos_to_string(root_pos)
+			.. " but the node at this location was " .. root_node.name)
+		return nil
+	end
+	
 	local root_hash = minetest.hash_node_position(root_pos)
-	local digtron_nodes = {[root_hash] = node} -- Nodes that are part of Digtron.
+	local digtron_nodes = {[root_hash] = root_node} -- Nodes that are part of Digtron.
 		-- Initialize with the controller, it won't be added by get_all_adjacent_digtron_nodes
 	local digtron_adjacent = {} -- Nodes that are adjacent to Digtron but not a part of it.
 	-- There's a slight inefficiency in throwing away digtron_adjacent when retrieve_all_adjacent_pos could
@@ -326,9 +326,9 @@ digtron.assemble = function(root_pos, player_name)
 		layout[relative_hash] = {meta = current_meta_table, node = node}
 	end
 	
-	digtron.set_name(digtron_id, root_meta:get_string("infotext"))
 	persist_inventory(digtron_id)
 	persist_layout(digtron_id, layout)
+	set_name(digtron_id, digtron_name)
 	invalidate_layout_cache(digtron_id)
 	persist_pos(digtron_id, root_pos)
 	
@@ -394,8 +394,7 @@ local get_valid_data = function(digtron_id, root_pos, hash, data, function_name)
 end
 
 -- Turns the Digtron back into pieces
-digtron.disassemble = function(digtron_id, player_name)
-	local bbox = retrieve_bounding_box(digtron_id)
+local disassemble = function(digtron_id, player_name)
 	local root_pos = retrieve_pos(digtron_id)
 	if not root_pos then
 		minetest.log("error", "[Digtron] digtron.disassemble was unable to find a position for " .. digtron_id
@@ -403,11 +402,8 @@ digtron.disassemble = function(digtron_id, player_name)
 		return
 	end
 
-	local root_meta = minetest.get_meta(root_pos)
-	root_meta:set_string("infotext", digtron.get_name(digtron_id))
-	
 	local layout = retrieve_layout(digtron_id)
-	local inv = digtron.retrieve_inventory(digtron_id)
+	local inv = retrieve_inventory(digtron_id)
 	
 	if not (layout and inv) then
 		minetest.log("error", "[Digtron] digtron.disassemble was unable to find either layout or inventory record for " .. digtron_id
@@ -451,7 +447,16 @@ digtron.disassemble = function(digtron_id, player_name)
 			-- Clear digtron_id, this node is no longer part of an active digtron
 			node_meta:set_string("digtron_id", "")
 		end
-	end	
+	end
+	
+	-- replace the controller node with the disassembled version
+	local root_node = minetest.get_node(root_pos)
+	if root_node.name == "digtron:controller" then
+		root_node.name = "digtron:controller_disassembled"
+		minetest.set_node(root_pos, root_node)
+	end
+	local root_meta = minetest.get_meta(root_pos)
+	root_meta:set_string("infotext", get_name(digtron_id))
 
 	minetest.log("action", "Digtron " .. digtron_id .. " disassembled at " .. minetest.pos_to_string(root_pos)
 		.. " by " .. player_name)
@@ -468,7 +473,7 @@ end
 -- Removes the in-world nodes of a digtron
 -- Does not destroy its layout info
 -- returns a table of vectors of all the nodes that were removed
-digtron.remove_from_world = function(digtron_id, player_name)
+local remove_from_world = function(digtron_id, player_name)
 	local layout = retrieve_layout(digtron_id)
 	local root_pos = retrieve_pos(digtron_id)
 	
@@ -504,7 +509,7 @@ digtron.remove_from_world = function(digtron_id, player_name)
 end
 
 -- Tests if a Digtron can be built at the designated location
-digtron.is_buildable_to = function(digtron_id, layout, root_pos, player_name, ignore_nodes, return_immediately_on_failure)
+local is_buildable_to = function(digtron_id, layout, root_pos, player_name, ignore_nodes, return_immediately_on_failure)
 	-- If this digtron is already in-world, we're likely testing as part of a movement attempt.
 	-- Record its existing node locations, they will be treated as buildable_to
 	local old_root_pos = retrieve_pos(digtron_id)
@@ -557,10 +562,11 @@ digtron.is_buildable_to = function(digtron_id, layout, root_pos, player_name, ig
 end
 
 -- Places the Digtron into the world.
-digtron.build_to_world = function(digtron_id, layout, root_pos, player_name)
+local build_to_world = function(digtron_id, layout, root_pos, player_name)
 	if layout == nil then
 		layout = retrieve_layout(digtron_id)
 	end
+	local built_positions = {}
 	for hash, data in pairs(layout) do
 		-- Don't use get_valid_data, the Digtron isn't in-world yet
 		local node_pos = vector.add(minetest.get_position_from_hash(hash), root_pos)
@@ -571,18 +577,19 @@ digtron.build_to_world = function(digtron_id, layout, root_pos, player_name)
 		end
 		meta:set_string("digtron_id", digtron_id)
 		meta:mark_as_private("digtron_id")
+		table.insert(built_positions, node_pos)
 	end
 	persist_pos(digtron_id, root_pos)
 	
-	return true
+	return built_positions
 end
 
-digtron.move = function(digtron_id, dest_pos, player_name)
+local move = function(digtron_id, dest_pos, player_name)
 	local layout = retrieve_layout(digtron_id)
-	local permitted, succeeded, failed = digtron.is_buildable_to(digtron_id, layout, dest_pos, player_name)
+	local permitted, succeeded, failed = is_buildable_to(digtron_id, layout, dest_pos, player_name)
 	if permitted then
-		local removed = digtron.remove_from_world(digtron_id, player_name)
-		digtron.build_to_world(digtron_id, layout, dest_pos, player_name)
+		local removed = remove_from_world(digtron_id, player_name)
+		build_to_world(digtron_id, layout, dest_pos, player_name)
 		minetest.sound_play("digtron_truck", {gain = 0.5, pos=dest_pos})
 		for _, removed_pos in ipairs(removed) do
 			minetest.check_for_falling(removed_pos)
@@ -646,13 +653,13 @@ local rotate_layout = function(digtron_id, axis)
 	return rotated_layout
 end
 
-digtron.rotate = function(digtron_id, axis, player_name)
+local rotate = function(digtron_id, axis, player_name)
 	local rotated_layout = rotate_layout(digtron_id, axis)
 	local root_pos = retrieve_pos(digtron_id)
-	local permitted, succeeded, failed = digtron.is_buildable_to(digtron_id, rotated_layout, root_pos, player_name)
+	local permitted, succeeded, failed = is_buildable_to(digtron_id, rotated_layout, root_pos, player_name)
 	if permitted then
-		local removed = digtron.remove_from_world(digtron_id, player_name)
-		digtron.build_to_world(digtron_id, rotated_layout, root_pos, player_name)
+		local removed = remove_from_world(digtron_id, player_name)
+		build_to_world(digtron_id, rotated_layout, root_pos, player_name)
 		minetest.sound_play("digtron_hydraulic", {gain = 0.5, pos=dest_pos})
 		persist_layout(digtron_id, rotated_layout)
 		-- Don't need to do fancy callback checking for digtron nodes since I made all those
@@ -947,7 +954,7 @@ local insert_or_eject = function(digtron_id, item_list, pos)
 	end
 end
 
-digtron.execute_cycle = function(digtron_id, player_name)
+local execute_cycle = function(digtron_id, player_name)
 	local old_root_pos = retrieve_pos(digtron_id)
 	local root_node = minetest.get_node(old_root_pos)
 	local root_facedir = root_node.param2
@@ -1005,7 +1012,7 @@ end
 -- If the digtron node has an assigned ID and a layout for that ID exists and
 -- a matching node exists in the layout then don't let it be dug.
 -- TODO: add protection check?
-digtron.can_dig = function(pos, digger)
+local can_dig = function(pos, digger)
 	local meta = minetest.get_meta(pos)
 	local digtron_id = meta:get_string("digtron_id")
 	if digtron_id == "" then
@@ -1025,7 +1032,7 @@ digtron.can_dig = function(pos, digger)
 		minetest.log("error", "[Digtron] can_dig was called on a " .. node.name .. " at location "
 			.. minetest.pos_to_string(pos) .. " that claimed to belong to " .. digtron_id
 			.. ". However, layout and/or location data are missing: " .. missing)
-		-- May be better to do this to prevent node duplication. But we're already in bug land here so tread gently.
+		-- TODO May be better to do this to prevent node duplication. But we're already in bug land here so tread gently.
 		--minetest.remove_node(pos)
 		--return false
 		return true
@@ -1053,7 +1060,7 @@ end
 
 -- put this on all Digtron nodes. If other inventory types are added (eg, batteries)
 -- update this.
-digtron.on_blast = function(pos, intensity)
+local on_blast = function(pos, intensity)
 	if intensity < 1.0 then return end -- The Almighty Digtron ignores weak-ass explosions
 
 	local meta = minetest.get_meta(pos)
@@ -1079,7 +1086,7 @@ end
 -- Use this inside other on_rightclicks for configuring Digtron nodes, this
 -- overrides if you're right-clicking with another Digtron node and assumes
 -- that you're trying to build it.
-digtron.on_rightclick = function(pos, node, clicker, itemstack, pointed_thing)
+local on_rightclick = function(pos, node, clicker, itemstack, pointed_thing)
 	local item_def = itemstack:get_definition()
 	if item_def.type == "node" and minetest.get_item_group(itemstack:get_name(), "digtron") > 0 then
 		local returnstack, success = minetest.item_place_node(itemstack, clicker, pointed_thing)
@@ -1115,3 +1122,29 @@ if minetest.get_modpath("creative") then
 		end
 	end
 end
+
+
+
+---------------------------------------------------------------------------------------------------------------------------
+-- External API
+
+-- node definition methods
+digtron.can_dig = can_dig
+digtron.on_blast = on_blast
+digtron.on_rightclick = on_rightclick
+
+digtron.get_name = get_name
+digtron.set_name = set_name
+digtron.get_pos = retrieve_pos
+digtron.get_bounding_box = retrieve_bounding_box
+
+digtron.retrieve_inventory = retrieve_inventory -- used by formspecs
+
+digtron.assemble = assemble
+digtron.disassemble = disassemble
+digtron.remove_from_world = remove_from_world
+digtron.is_buildable_to = is_buildable_to
+digtron.build_to_world = build_to_world
+digtron.move = move
+digtron.rotate = rotate
+digtron.execute_cycle = execute_cycle
\ No newline at end of file
diff --git a/init.lua b/init.lua
index 3415d18..c46c5af 100644
--- a/init.lua
+++ b/init.lua
@@ -1,6 +1,21 @@
 digtron = {}
 digtron.doc = {} -- TODO: move to doc file
 
+-- A global dictionary is used here so that other substitutions can be added easily by other mods, if necessary
+digtron.builder_read_item_substitutions = {
+	["default:torch_ceiling"] = "default:torch",
+	["default:torch_wall"] = "default:torch",
+	["default:dirt_with_grass"] = "default:dirt",
+	["default:dirt_with_grass_footsteps"] = "default:dirt",
+	["default:dirt_with_dry_grass"] = "default:dirt",
+	["default:dirt_with_rainforest_litter"] = "default:dirt",
+	["default:dirt_with_snow"] = "default:dirt",
+	["default:furnace_active"] = "default:furnace",
+	["farming:soil"] = "default:dirt",
+	["farming:soil_wet"] = "default:dirt",
+	["farming:desert_sand_soil"] = "default:desert_sand",
+	["farming:desert_sand_soil_wet"] = "default:desert_sand",
+}
 
 -- Sometimes we want builder heads to call an item's "on_place" method, other times we
 -- don't want them to. There's no way to tell which situation is best programmatically
diff --git a/nodes/node_builder.lua b/nodes/node_builder.lua
index e6ba720..2962aa2 100644
--- a/nodes/node_builder.lua
+++ b/nodes/node_builder.lua
@@ -23,17 +23,21 @@ local get_formspec = function(pos)
 	"listcolors[#00000069;#5A5A5A00;#141318;#30434C;#FFF]" ..
 	"list[detached:digtron:builder_item;main;0,0;1,1;]" ..
 	"field[1.3,0.8;1,0.1;extrusion;" .. S("Extrusion") .. ";" ..extrusion .. "]" ..
+	"field_close_on_enter[extrusion;false]" ..
 	"tooltip[extrusion;" .. S("Builder will extrude this many blocks in the direction it is facing.\nCan be set from 1 to @1.\nNote that Digtron won't build into unloaded map regions.", digtron.config.maximum_extrusion) .. "]" ..
 	"field[2.3,0.8;1,0.1;period;" .. S("Periodicity") .. ";".. period .. "]" ..
+	"field_close_on_enter[period;false]" ..
 	"tooltip[period;" .. S("Builder will build once every n steps.\nThese steps are globally aligned, so all builders with the\nsame period and offset will build on the same location.") .. "]" ..
 	"field[3.3,0.8;1,0.1;offset;" .. S("Offset") .. ";" .. offset .. "]" ..
+	"field_close_on_enter[offset;false]" ..
 	"tooltip[offset;" .. S("Offsets the start of periodicity counting by this amount.\nFor example, a builder with period 2 and offset 0 builds\nevery even-numbered block and one with period 2 and\noffset 1 builds every odd-numbered block.") .. "]" ..
 	"button[4.0,0.5;1,0.1;set;" .. S("Save &\nShow") .. "]" ..
-	"tooltip[set;" .. S("Saves settings") .. "]" ..
+	"tooltip[set;" .. S("Saves settings, closes interface, and shows the locations this builder will build to in-world.") .. "]" ..
 	"field[5.3,0.8;1,0.1;facing;" .. S("Facing") .. ";" .. facing .. "]" ..
+	"field_close_on_enter[facing;false]" ..
 	"tooltip[facing;" .. S("Value from 0-23. Not all block types make use of this.\nUse the 'Read & Save' button to copy the facing of the block\ncurrently in the builder output location.") .. "]" ..
-	"button[6.0,0.5;1,0.1;read;" .. S("Read &\nSave") .. "]" ..
-	"tooltip[read;" .. S("Reads the facing of the block currently in the build location,\nthen saves all settings.") .. "]" ..
+	"button[6.0,0.5;1,0.1;read;" .. S("Read") .. "]" ..
+	"tooltip[read;" .. S("Reads the facing of the block currently in the build location.") .. "]" ..
 	"list[current_player;main;0,1.3;8,1;]" ..
 	default.get_hotbar_bg(0,1.3) ..
 	"list[current_player;main;0,2.5;8,3;8]" ..
@@ -44,6 +48,19 @@ end
 ----------------------------------------------------------------------
 -- Detached inventory for setting the builder item
 
+local is_item_allowed = function(item)
+	-- Ignore unknown items
+	if minetest.registered_items[item] == nil then return false end
+
+	local stack_def = minetest.registered_nodes[item]
+	if not stack_def and not digtron.whitelisted_on_place(item) then
+		return false -- don't allow craft items unless their on_place is whitelisted.
+	end
+	
+	return true
+end
+
+
 local inv = minetest.create_detached_inventory("digtron:builder_item", {
 	allow_move = function(inv, from_list, from_index, to_list, to_index, count, player)
 		return 0
@@ -52,9 +69,10 @@ local inv = minetest.create_detached_inventory("digtron:builder_item", {
 		-- Always disallow put, but use this to read what the player *tried* adding and set the builder appropriately
 		local item = stack:get_name()
 		
-		-- Ignore unknown items
-		if minetest.registered_items[item] == nil then return 0 end
-		
+		if not is_item_allowed(item) then
+			return 0
+		end
+
 		local player_name = player:get_player_name()
 		local pos = player_interacting_with_builder_pos[player_name]
 		if pos == nil then
@@ -78,11 +96,6 @@ local inv = minetest.create_detached_inventory("digtron:builder_item", {
 			return 0
 		end
 		
-		local stack_def = minetest.registered_nodes[item]
-		if not stack_def and not digtron.whitelisted_on_place(item) then
-			return 0 -- don't allow craft items unless their on_place is whitelisted.
-		end
-		
 		-- If we're adding a wallmounted item and the build facing is greater than 5, reset it to 0
 		if stack_def ~= nil and stack_def.paramtype2 == "wallmounted" and tonumber(meta:get_int("facing")) > 5 then
 			meta:set_int("facing", 0)
@@ -97,12 +110,6 @@ local inv = minetest.create_detached_inventory("digtron:builder_item", {
 	allow_take = function(inv, listname, index, stack, player)
 		return 0
 	end,
---	on_move = function(inv, from_list, from_index, to_list, to_index, count, player)
---	end,
---	on_take = function(inv, listname, index, stack, player)
---	end,
---	on_put = function(inv, listname, index, stack, player)
---	end
 })
 inv:set_size("main", 1)
 
@@ -142,30 +149,31 @@ minetest.register_on_player_receive_fields(function(sender, formname, fields)
 			.. " no position was recorded.")
 		return
 	end
-
+	
     local meta = minetest.get_meta(pos)
-	local period = tonumber(fields.period)
-	local offset = tonumber(fields.offset)
-	local facing = tonumber(fields.facing)
-	local extrusion = tonumber(fields.extrusion)
 	
 	local item = meta:get_string("item")
 	
+	local period = tonumber(fields.period)
 	if period and period > 0 then
 		meta:set_int("period", math.floor(period))
 	else
 		period = meta:get_int("period")
 	end
+	
+	local offset = tonumber(fields.offset)
 	if offset then
 		meta:set_int("offset", math.floor(offset))
 	else
 		offset = meta:get_int("offset")
 	end
+	
+	local facing = tonumber(fields.facing)
 	if facing and facing >= 0 and facing < 24 then
 		local target_item = ItemStack(item)
 		if target_item:get_definition().paramtype2 == "wallmounted" then
 			if facing < 6 then
-				meta:set_int("facing", facing)
+				meta:set_int("facing", math.floor(facing))
 				-- wallmounted facings only run from 0-5
 			end
 		else
@@ -175,27 +183,32 @@ minetest.register_on_player_receive_fields(function(sender, formname, fields)
 		facing = meta:get_int("facing")
 	end
 	
+	local extrusion = tonumber(fields.extrusion)
 	if extrusion and extrusion > 0 and extrusion <= digtron.config.maximum_extrusion then
 		meta:set_int("extrusion", math.floor(extrusion))
 	else
 		extrusion = meta:get_int("extrusion")
 	end
 	
---	if fields.set then
---		digtron.show_offset_markers(pos, offset, period)
---
---	elseif fields.read then
---		local facing = minetest.get_node(pos).param2
---		local buildpos = digtron.find_new_pos(pos, facing)
---		local target_node = minetest.get_node(buildpos)
---		if target_node.name ~= "air" and minetest.get_item_group(target_node.name, "digtron") == 0 then
---			local meta = minetest.get_meta(pos)
---			local inv = meta:get_inventory()
---			local target_name = digtron.builder_read_item_substitutions[target_node.name] or target_node.name
---			inv:set_stack("main", 1, target_name)
---			meta:set_int("facing", target_node.param2)
---		end
---	end
+	if fields.set then
+		--digtron.show_offset_markers(pos, offset, period)
+	end
+
+	if fields.read then
+		local builder_facing = minetest.get_node(pos).param2
+		local buildpos = vector.add(minetest.facedir_to_dir(builder_facing), pos)
+		local target_node = minetest.get_node(buildpos)
+		local target_name = target_node.name
+		if digtron.builder_read_item_substitutions[target_name] then
+			target_name = digtron.builder_read_item_substitutions[target_name]
+		end
+		if target_name ~= "air" and is_item_allowed(target_name) then
+			local meta = minetest.get_meta(pos)
+			item = target_name
+			meta:set_string("item", item)
+			meta:set_int("facing", target_node.param2)
+		end
+	end
 	
 	if fields.help then
 		minetest.after(0.5, doc.show_entry, sender:get_player_name(), "nodes", "digtron:builder", true)
@@ -208,8 +221,9 @@ minetest.register_on_player_receive_fields(function(sender, formname, fields)
 	end
 	
 	meta:set_string("infotext", S("Builder for @1\nperiod @2, offset @3, extrusion @4", item_desc, period, offset, extrusion))
-	
 	digtron.update_builder_item(pos)
+	minetest.show_formspec(player_name, "digtron:builder", get_formspec(pos))
+
 end)