diff --git a/fs_edit_preconditions.lua b/fs_edit_preconditions.lua
index 7d0be79..cab5108 100644
--- a/fs_edit_preconditions.lua
+++ b/fs_edit_preconditions.lua
@@ -1,4 +1,82 @@
 
+-- some helper lists for creating the formspecs and evaulating
+-- the player's answers
+
+-- general direction of what a prerequirement may be about
+local check_what = {
+	"- please select -",
+	"an internal state (i.e. of a quest)", -- 2
+	"a block somewhere", -- 3
+	"a trade", -- 4
+	"the inventory of the player", -- 5
+	"the inventory of the NPC", -- 6
+}
+
+-- options for "a trade"
+local check_trade = {
+	"- please select -",
+	"The NPC has the item(s) he wants to sell in his inventory.",
+	"The player has the item(s) needed to pay the price.",
+	"The NPC ran out of stock.",
+	"The player cannot afford the price.",
+}
+
+-- options for "the inventory of " (either player or NPC; perhaps blocks later on)
+local check_inv = {
+	"- please select -",
+	"The inventory contains the following item:",
+	"The inventory *does not* contain the following item:",
+	"There is room for the following item in the inventory:",
+	"The inventory is empty.",
+}
+
+local check_block = {
+	"- please select -",
+	"The block is as it is now.",
+	"There shall be air instead of this block.",
+	"The block is diffrent from how it is now.",
+	"I can't punch it. The block is as the block *above* the one I punched.",
+}
+
+-- comparison operators for variables
+local check_operator = {
+	"- please select -", -- 1
+	"== (is equal)", -- 2
+	"~= (is not equal)", -- 3
+	">= (is greater or equal)", -- 4
+	">  (is greater)", -- 5
+	"<= (is smaller or equal)", -- 6
+	"<  (is smaller)", -- 7
+	"not (logically invert)", -- 8
+	"is_set (has a value)", -- 9
+	"is_unset (has no value)" -- 10
+}
+
+-- some internal ones...
+local check_variable = {
+	"- please select -",
+	"(internal) hour of ingame day",
+	"(internal) player's health points",
+}
+
+
+-- TODO: check inscription of a sign?
+-- TODO: invlist as dropdown of inventory lists at detected position
+-- TODO: variable as dropdown of allowed variables
+
+-- which diffrent types of preconditions are available?
+-- possible variables:
+-- 	item		an inventory item or block (check if it exists)
+-- 		-> needs to be a minetest.registered_item[ item ]
+-- 	text		some text
+-- 	pos		a position in the world (not too far from the NPC)
+-- 		-> determined by punching
+-- 	variable	name of a variable
+--
+-- TODO: may all boil down to automaticly setting some lua code?
+--       -> better write a function for each one that can be called when needed
+
+
 yl_speak_up.input_fs_edit_preconditions = function(player, formname, fields)
 	if(not(player)) then
 		return
@@ -8,12 +86,65 @@ yl_speak_up.input_fs_edit_preconditions = function(player, formname, fields)
 	local n_id = yl_speak_up.speak_to[pname].n_id
 	local d_id = yl_speak_up.speak_to[pname].d_id
 	local o_id = yl_speak_up.speak_to[pname].o_id
+	local p_id = yl_speak_up.speak_to[pname].p_id
 
 	-- this only works in edit mode
 	if(not(n_id) or yl_speak_up.edit_mode[pname] ~= n_id) then
 		return
 	end
 
+	-- TODO: make delete work
+	-- TODO: make save work
+	-- TODO: check parameters
+
+	if(fields.select_block_pos) then
+		minetest.chat_send_player(pname,
+			"Please punch the block you want to check in your precondition!")
+		-- this formspec expects the block punch:
+		yl_speak_up.speak_to[pname].expect_block_punch = "edit_preconditions"
+		return
+	end
+
+	-- select a general direction/type first
+	if(fields.select_what) then
+		local nr = table.indexof(check_what, fields.select_what)
+		yl_speak_up.speak_to[pname].tmp_prereq = { what = nr }
+
+	-- select a subtype for the "a trade" selection
+	elseif(fields.select_trade) then
+		local nr = table.indexof(check_trade, fields.select_trade)
+		yl_speak_up.speak_to[pname].tmp_prereq.trade = nr
+
+	-- select a subtype for the inventory selection (player or NPC)
+	elseif(fields.select_inv) then
+		local nr = table.indexof(check_inv, fields.select_inv)
+		yl_speak_up.speak_to[pname].tmp_prereq.inv = nr
+
+	-- select data regarding a block
+	elseif(fields.select_block) then
+		local nr = table.indexof(check_block, fields.select_block)
+		yl_speak_up.speak_to[pname].tmp_prereq.block = nr
+
+	-- select data regarding a variable
+	elseif(fields.select_variable) then
+		-- TODO: this needs to include player-specific variables
+		local nr = table.indexof(check_variable, fields.select_variable)
+		yl_speak_up.speak_to[pname].tmp_prereq.variable = nr
+
+	-- select data regarding an operator
+	elseif(fields.select_operator) then
+		local nr = table.indexof(check_operator, fields.select_operator)
+		yl_speak_up.speak_to[pname].tmp_prereq.operator = nr
+	end
+
+	-- the player wants to change/edit a precondition
+	if(fields.change_prereq or fields.select_what or fields.select_trade
+	  or fields.select_inv or fields.select_block
+	  or fields.select_variable or fields.select_operator) then
+		yl_speak_up.show_fs(player, "edit_preconditions")
+		return
+	end
+
 	-- go back to the edit option dialog
 	yl_speak_up.show_fs(player, "edit_option_dialog",
 		{n_id = n_id, d_id = d_id, o_id = o_id, caller="edit_precondition"})
@@ -21,7 +152,7 @@ end
 
 
 yl_speak_up.get_fs_edit_preconditions = function(player, table_click_result)
-	if(not(player) or not(table_click_result)) then
+	if(not(player)) then
 		return ""
 	end
 	local pname = player:get_player_name()
@@ -29,6 +160,7 @@ yl_speak_up.get_fs_edit_preconditions = function(player, table_click_result)
 	local n_id = yl_speak_up.speak_to[pname].n_id
 	local d_id = yl_speak_up.speak_to[pname].d_id
 	local o_id = yl_speak_up.speak_to[pname].o_id
+	local p_id = yl_speak_up.speak_to[pname].p_id
 
 	-- this only works in edit mode
 	if(not(n_id) or yl_speak_up.edit_mode[pname] ~= n_id) then
@@ -47,17 +179,176 @@ yl_speak_up.get_fs_edit_preconditions = function(player, table_click_result)
 	if(not(prereq)) then
 		prereq = {}
 	end
-	-- which precondition has the player selected?
-	local sorted_key_list = yl_speak_up.sort_keys(prereq)
-	local selected = minetest.explode_table_event(table_click_result)
-	-- use "new" if nothing fits
-	local p_id = "new"
-	if((selected.type == "CHG" or selected.type == "DLC")
-	  and selected.row <= #sorted_key_list) then
-		p_id = sorted_key_list[ selected.row ]
+
+	-- did we arrive here through clicking on a prereq in the dialog edit options menu?
+	if(table_click_result) then
+		-- which precondition has the player selected?
+		local sorted_key_list = yl_speak_up.sort_keys(prereq)
+		local selected = minetest.explode_table_event(table_click_result)
+		-- use "new" if nothing fits
+		p_id = "new"
+		if((selected.type == "CHG" or selected.type == "DLC")
+		  and selected.row <= #sorted_key_list) then
+			p_id = sorted_key_list[ selected.row ]
+		end
+
+		-- store which prereq we are talking about
+		yl_speak_up.speak_to[pname].p_id = p_id
+		-- display the selected prereq
+		if(p_id ~= "new") then
+			return "formspec_version[3]"..
+				"size[20,3]"..
+				"bgcolor[#00000000;false]"..
+				"label[0.2,0.5;Selected pre(C)ondition:]"..
+				"tablecolumns[text;color,span=1;text;text]"..
+				"table[0.2,0.8;19.6,0.7;table_of_preconditions;"..
+					minetest.formspec_escape(prereq[ p_id ].p_id)..",#FFFF00,"..
+					minetest.formspec_escape(prereq[ p_id ].p_type)..","..
+					minetest.formspec_escape(prereq[ p_id ].p_value)..";0]"..
+				"button[2.0,1.8;1.5,0.9;delete_prereq;Delete]"..
+				"button[4.0,1.8;1.5,0.9;change_prereq;Change]"..
+				"button[6.0,1.8;1,0.9;back;Back]"
+		end
 	end
 
-	minetest.chat_send_player("singleplayer","input: "..minetest.serialize(table_click_result))
-	return "size[4,1.5]label[0,0;Formspec: edit preconditions\n-> "..tostring(p_id).."]"..
-		"button[1,1.0;1,1.0;back;Back]"
+	-- did the player get here through punching a block in the meantime?
+	local block_pos = yl_speak_up.speak_to[pname].block_punched
+	yl_speak_up.speak_to[pname].block_punched = nil
+
+	local data = yl_speak_up.speak_to[pname].tmp_prereq
+	if(not(data) or not(data.what)) then
+		data = { what = 1}
+	end
+	-- fallback
+	if(not(p_id)) then
+		p_id = "new"
+	end
+	local save_button = "button[5.0,9.0;1,0.7;save_prereq;Save]"
+	local formspec =
+		"formspec_version[3]"..
+		"size[20,10]"..
+		"label[5,0.5;Edit pre(C)ondition \""..minetest.formspec_escape(p_id).."\"]"..
+		"label[0.2,1.5;What do you want to check in this precondition?]"..
+		"label[0.2,2.0;Something regarding...]"..
+		"dropdown[4.0,1.8;14.0,0.6;select_what;"..
+			table.concat(check_what, ",")..";"..
+			tostring(data.what)..";]"..
+		"button[3.0,9.0;1,0.7;back;Abort]"
+
+	-- "an internal state (i.e. of a quest)", -- 2
+	if(data.what and data.what == 2) then
+		if(not(data.variable) or data.variable == 1) then
+			data.variable = 1
+			-- not enough selected yet for saving
+			save_button = ""
+		elseif(not(data.operator) or data.operator == 1) then
+			data.operator = 1
+			save_button = ""
+		end
+		local field_for_value = "field[11.2,4.8;7.0,0.6;var_cmp_value;;]"
+		-- do not show value input field for unary operators
+		if(not(data.operator) or data.operator == 1 or data.operator >= 8) then
+			field_for_value = "label[11.2,5.1;- not used for this operator -]"
+		end
+		-- TODO: the list of available variables needs to be extended
+		--       with the ones the player has read access to
+		formspec = formspec..
+			"label[0.2,3.3;The following expression shall be true:]"..
+			"label[0.2,4.3;Name of variable:]"..
+			"dropdown[0.2,4.8;6.5,0.6;select_variable;"..
+				table.concat(check_variable, ",")..";"..
+				tostring(data.variable)..";]"..
+			"label[7.0,4.3;Operator:]"..
+			"dropdown[7.0,4.8;4.0,0.6;select_operator;"..
+				table.concat(check_operator, ",")..";"..
+				tostring(data.operator)..";]"..
+			"label[11.2,4.3;Value to compare with:]"..
+			field_for_value
+
+	-- "a trade", -- 4
+	elseif(data.what and data.what == 4) then
+		if(not(data.trade) or data.trade == 1) then
+			data.trade = 1
+			-- not enough selected yet for saving
+			save_button = ""
+		end
+		formspec = formspec..
+			"label[0.2,3.3;If the action is a trade, the following shall be true:]"..
+			"dropdown[4.0,3.5;16.0,0.6;select_trade;"..
+				table.concat(check_trade, ",")..";"..
+				tostring(data.trade)..";]"
+
+	-- "the inventory of the player", -- 5
+	-- "the inventory of the NPC", -- 6
+	elseif(data.what and data.what >= 5 and data.what <= 6) then
+		if(not(data.inv) or data.inv == 1) then
+			data.inv = 1
+			-- not enough selected yet for saving
+			save_button = ""
+		end
+		formspec = formspec..
+			"label[0.2,3.3;The following shall be true about the inventory:]"..
+			"dropdown[4.0,3.5;16.0,0.6;select_inv;"..
+				table.concat(check_inv, ",")..";"..
+				tostring(data.inv)..";]"..
+			"label[0.2,4.5;Name of the item(stack):]"..
+			"field[4.0,4.3;16.0,0.6;inv_stack_name;;]"..
+			"tooltip[inv_stack_name;Enter name of the block and amount.\n"..
+				"Example: \"default:apple 3\" for three apples,\n"..
+				"         \"farming:bread\" for a bread.]"
+
+	-- "a block somewhere", -- 3
+	elseif(data.what and data.what == 3) then
+		local block_pos_str = "- none set -"
+		local node = {name = "- unknown -", param2 = "- unkown -"}
+		if(not(block_pos) and data and data.block_pos) then
+			block_pos = data.block_pos
+		end
+		if(block_pos) then
+			-- store for later usage
+			data.block_pos = block_pos
+			tmp_pos = {x=block_pos.x, y=block_pos.y, z=block_pos.z}
+			-- "I can't punch it. The block is as the block *above* the one I punched.",
+			if(data.block and data.block == 5) then
+				tmp_pos.y = block_pos.y + 1
+			end
+			block_pos_str = minetest.pos_to_string(tmp_pos)
+			node = minetest.get_node_or_nil(tmp_pos)
+			if(not(node)) then
+				node = {name = "- unknown -", param2 = "- unkown -"}
+			end
+			-- "There shall be air instead of this block.",
+			if(data.block and data.block == 3) then
+				node = {name = "air", param2 = 0}
+			end
+			-- cache that (in case a sapling grows or someone else changes it)
+			data.node_data = node
+		end
+		if(node.name == "- unknown -") then
+			save_button = ""
+		end
+		if(not(data.block) or data.block == 1) then
+			data.block = 1
+			-- not enough selected yet for saving
+			save_button = ""
+		end
+		formspec = formspec..
+			"label[0.2,3.3;The following shall be true about the block:]"..
+			"dropdown[4.0,3.5;16.0,0.6;select_block;"..
+				table.concat(check_block, ",")..";"..
+				tostring(data.block)..";]"..
+			"label[0.2,4.8;Position of the block:]"..
+			"label[4.0,4.8;"..minetest.formspec_escape(block_pos_str).."]"..
+			"label[0.2,5.8;Name of block:]"..
+			"label[4.0,5.8;"..minetest.formspec_escape(node.name).."]"..
+			"label[0.2,6.8;Orientation (param2):]"..
+			"label[4.0,6.8;"..minetest.formspec_escape(node.param2).."]"..
+			"button_exit[10.0,5.5;4.0,0.7;select_block_pos;Set position of block]"..
+			"tooltip[select_block_pos;Click on this button to select a block.\n"..
+				"This menu will close and you will be asked to punch\n"..
+				"the block at the position you want to check.\n"..
+				"After punching it, you will be returned to this menu.]"
+	end
+
+	return formspec..save_button
 end