diff --git a/cybersyn/scripts/global.lua b/cybersyn/scripts/global.lua
index 449030a..569b43b 100644
--- a/cybersyn/scripts/global.lua
+++ b/cybersyn/scripts/global.lua
@@ -2,6 +2,7 @@
 ---@class MapData
 ---@field public total_ticks uint
 ---@field public layout_top_id uint
+---@field public to_comb {[uint]: LuaEntity}
 ---@field public to_output {[uint]: LuaEntity}
 ---@field public to_stop {[uint]: LuaEntity}
 ---@field public stations {[uint]: Station}
@@ -56,6 +57,7 @@ mod_settings.r_threshold = settings.global["cybersyn-request-threshold"].value
 mod_settings.p_threshold = settings.global["cybersyn-provide-threshold"].value
 
 global.total_ticks = 0
+global.to_comb = {}
 global.to_output = {}
 global.to_stop = {}
 global.stations = {}
diff --git a/cybersyn/scripts/gui.lua b/cybersyn/scripts/gui.lua
index 9c3c493..42aff8c 100644
--- a/cybersyn/scripts/gui.lua
+++ b/cybersyn/scripts/gui.lua
@@ -1,5 +1,6 @@
 --By Mami
-local gui = require("__flib__.gui")
+local flib_gui = require("__flib__.gui")
+local flib_event = require("__flib__.event")
 
 local RED = "utility/status_not_working"
 local GREEN = "utility/status_working"
@@ -25,11 +26,24 @@ STATUS_NAMES[defines.entity_status.disabled_by_script] = "entity-status.disabled
 STATUS_NAMES[defines.entity_status.marked_for_deconstruction] = "entity-status.marked-for-deconstruction"
 STATUS_NAMES_DEFAULT = "entity-status.disabled"
 
----@param entity LuaEntity
-function gui_opened(entity, player)
+---@param comb LuaEntity
+---@param player LuaPlayer
+function gui_opened(comb, player)
 	local rootgui = player.gui.screen
-	local window = gui.build(rootgui, {
-		{type="frame", direction="vertical", ref={"main_window"}, name=COMBINATOR_NAME, tags={unit_number=entity.unit_number}, actions={
+	local selected_index = 0
+	local control = comb.get_or_create_control_behavior().parameters
+	if control.operation == OPERATION_PRIMARY_IO then
+		selected_index = 1
+	elseif control.operation == OPERATION_SECONDARY_IO then
+		selected_index = 2
+	elseif control.operation == OPERATION_DEPOT then
+		selected_index = 3
+	elseif control.operation == OPERATION_WAGON_MANIFEST then
+		selected_index = 4
+	end
+
+	local window = flib_gui.build(rootgui, {
+		{type="frame", direction="vertical", ref={"main_window"}, name=COMBINATOR_NAME, actions={
 			on_close = {"test"}
 		}, children={
 			--title bar
@@ -37,15 +51,15 @@ function gui_opened(entity, player)
 				{type="label", style="frame_title", caption={"cybersyn-gui.combinator-title"}, elem_mods={ignored_by_interaction=true}},
 				{type="empty-widget", style="flib_titlebar_drag_handle", elem_mods={ignored_by_interaction=true}},
 				{type="sprite-button", style="frame_action_button", mouse_button_filter={"left"}, sprite="utility/close_white", hovered_sprite="utility/close_black", name=COMBINATOR_NAME, actions={
-					on_click = {"test"}
+					on_click = {"close", comb.unit_number}
 				}}
 			}},
 			{type="frame", style="inside_shallow_frame_with_padding", style_mods={padding=8}, children={
 				{type="flow", direction="vertical", style_mods={horizontal_align="left"}, children={
 					--status
 					{type="flow", style = "status_flow", direction = "horizontal", style_mods={vertical_align="center", horizontally_stretchable=true}, children={
-						{type="sprite", sprite=STATUS_SPRITES[entity.status] or STATUS_SPRITES_DEFAULT, style="status_image", ref={"status_icon"}, style_mods={stretch_image_to_widget_size=true}},
-						{type="label", caption={STATUS_NAMES[entity.status] or STATUS_NAMES_DEFAULT}, ref={"status_label"}}
+						{type="sprite", sprite=STATUS_SPRITES[comb.status] or STATUS_SPRITES_DEFAULT, style="status_image", ref={"status_icon"}, style_mods={stretch_image_to_widget_size=true}},
+						{type="label", caption={STATUS_NAMES[comb.status] or STATUS_NAMES_DEFAULT}, ref={"status_label"}}
 					}},
 					--preview
 					{type="frame", style="deep_frame_in_shallow_frame", style_mods={minimal_width=0, horizontally_stretchable=true, padding=0}, children={
@@ -53,8 +67,8 @@ function gui_opened(entity, player)
 					}},
 					{type="label", caption={"cybersyn-gui.operation"}, style_mods={top_padding=8}},
 					{type="drop-down", ref={"operation"}, actions={
-						on_selection_state_changed = {"test"}
-					}, items={
+						on_selection_state_changed = {"drop-down", comb.unit_number}
+					}, selected_index=selected_index, items={
 						{"cybersyn-gui.comb1"},
 						{"cybersyn-gui.comb2"},
 						{"cybersyn-gui.depot"},
@@ -65,34 +79,71 @@ function gui_opened(entity, player)
 		}}
 	})
 
-	window.preview.entity = entity
+	window.preview.entity = comb
 	window.titlebar.drag_target = window.main_window
 	window.main_window.force_auto_center()
 
 	player.opened = window.main_window
 end
 
-local function o(event)
+local function on_gui_opened(event)
 	local entity = event.entity
-	if not entity or not entity.valid then return end
+	if not entity or not entity.valid or entity.name ~= COMBINATOR_NAME then return end
+	local player = game.get_player(event.player_index)
+	if not player then return end
+
+	gui_opened(entity, player)
+end
+
+local function on_gui_closed(event)
+	if not event.element or event.element.name ~= COMBINATOR_NAME then return end
 	local player = game.get_player(event.player_index)
 	if not player then return end
 	local rootgui = player.gui.screen
 
 	if rootgui[COMBINATOR_NAME] then
-		--rootgui[COMBINATOR_NAME].destroy()
-	else
-		gui_opened(entity, player)
+		rootgui[COMBINATOR_NAME].destroy()
+		--TODO: play close sound to player
 	end
 end
 
 function register_gui_actions()
-	gui.hook_events(function(event)
-		local msg = gui.read_action(event)
+	flib_gui.hook_events(function(event)
+		local msg = flib_gui.read_action(event)
 		if msg then
+			local player = game.get_player(event.player_index)
+			if not player then return end
+			local rootgui = player.gui.screen
 			-- read the action to determine what to do
-			local hi = 2
+			if msg[1] == "close" then
+				if rootgui[COMBINATOR_NAME] then
+					rootgui[COMBINATOR_NAME].destroy()
+					--TODO: play close sound to player
+				end
+			elseif msg[1] == "drop-down" then
+				local element = event.element
+				if not element then return end
+				local comb = global.to_comb[msg[2]]
+				if not comb or not comb.valid then return end
+
+				local a = comb.get_or_create_control_behavior()
+				local control = a.parameters
+				if element.selected_index == 1 then
+					control.operation = OPERATION_PRIMARY_IO
+				elseif element.selected_index == 2 then
+					control.operation = OPERATION_SECONDARY_IO
+				elseif element.selected_index == 3 then
+					control.operation = OPERATION_DEPOT
+				elseif element.selected_index == 4 then
+					control.operation = OPERATION_WAGON_MANIFEST
+				else
+					return
+				end
+				a.parameters = control
+				on_combinator_updated(global, comb)
+			end
 		end
 	end)
-	script.on_event(defines.events.on_gui_opened, o)
+	flib_event.register(defines.events.on_gui_opened, on_gui_opened)
+	flib_event.register(defines.events.on_gui_closed, on_gui_closed)
 end
diff --git a/cybersyn/scripts/layout.lua b/cybersyn/scripts/layout.lua
index 5dafdfa..6831692 100644
--- a/cybersyn/scripts/layout.lua
+++ b/cybersyn/scripts/layout.lua
@@ -107,7 +107,7 @@ local function reset_station_layout(map_data, station, forbidden_entity)
 		direction_filter = {defines.direction.east, defines.direction.west}
 		is_ver = true
 	elseif station_direction == defines.direction.east then
-		search_area = {left_top = {y = middle_y - reach, x = middle_x}, right_bottom = {y = middle_y + reach, x = middle_x - 6}}
+		search_area = {left_top = {y = middle_y - reach, x = middle_x - 6}, right_bottom = {y = middle_y + reach, x = middle_x}}
 		area_delta = {x = -7, y = 0}
 		direction_filter = {defines.direction.north, defines.direction.south}
 		is_ver = false
@@ -117,7 +117,7 @@ local function reset_station_layout(map_data, station, forbidden_entity)
 		direction_filter = {defines.direction.east, defines.direction.west}
 		is_ver = true
 	elseif station_direction == defines.direction.west then
-		search_area = {left_top = {y = middle_y - reach, x = middle_x + 6}, right_bottom = {y = middle_y + reach, x = middle_x}}
+		search_area = {left_top = {y = middle_y - reach, x = middle_x}, right_bottom = {y = middle_y + reach, x = middle_x + 6}}
 		area_delta = {x = 7, y = 0}
 		direction_filter = {defines.direction.north, defines.direction.south}
 		is_ver = false
diff --git a/cybersyn/scripts/main.lua b/cybersyn/scripts/main.lua
index 2d69b9b..4baf7f6 100644
--- a/cybersyn/scripts/main.lua
+++ b/cybersyn/scripts/main.lua
@@ -1,4 +1,5 @@
 --By Mami
+local flib_event = require("__flib__.event")
 
 ---@param map_data MapData
 ---@param train Train
@@ -151,6 +152,7 @@ local function on_combinator_built(map_data, comb)
 		wire = defines.wire_type.red,
 	})
 
+	map_data.to_comb[comb.unit_number] = comb
 	map_data.to_output[comb.unit_number] = out
 	map_data.to_stop[comb.unit_number] = stop
 
@@ -229,12 +231,13 @@ local function on_combinator_broken(map_data, comb)
 	if out and out.valid then
 		out.destroy()
 	end
+	map_data.to_comb[comb.unit_number] = nil
 	map_data.to_output[comb.unit_number] = nil
 	map_data.to_stop[comb.unit_number] = nil
 end
 ---@param map_data MapData
 ---@param comb LuaEntity
-local function on_combinator_updated(map_data, comb)
+function on_combinator_updated(map_data, comb)
 	--NOTE: this is the lazy way to implement updates and puts strong restrictions on data validity on on_combinator_broken
 	on_combinator_broken(map_data, comb)
 	on_combinator_built(map_data, comb)
@@ -588,40 +591,39 @@ local filter_broken = {
 }
 local function register_events()
 	--NOTE: I have no idea if this correctly registers all events once in all situations
-	script.on_event(defines.events.on_built_entity, on_built, filter_built)
-	script.on_event(defines.events.on_robot_built_entity, on_built, filter_built)
-	script.on_event({defines.events.script_raised_built, defines.events.script_raised_revive, defines.events.on_entity_cloned}, on_built)
+	flib_event.register(defines.events.on_built_entity, on_built, filter_built)
+	flib_event.register(defines.events.on_robot_built_entity, on_built, filter_built)
+	flib_event.register({defines.events.script_raised_built, defines.events.script_raised_revive, defines.events.on_entity_cloned}, on_built)
 
-	script.on_event(defines.events.on_pre_player_mined_item, on_broken, filter_broken)
-	script.on_event(defines.events.on_robot_pre_mined, on_broken, filter_broken)
-	script.on_event(defines.events.on_entity_died, on_broken, filter_broken)
-	script.on_event(defines.events.script_raised_destroy, on_broken)
+	flib_event.register(defines.events.on_pre_player_mined_item, on_broken, filter_broken)
+	flib_event.register(defines.events.on_robot_pre_mined, on_broken, filter_broken)
+	flib_event.register(defines.events.on_entity_died, on_broken, filter_broken)
+	flib_event.register(defines.events.script_raised_destroy, on_broken)
 
-	script.on_event({defines.events.on_pre_surface_deleted, defines.events.on_pre_surface_cleared}, on_surface_removed)
+	flib_event.register({defines.events.on_pre_surface_deleted, defines.events.on_pre_surface_cleared}, on_surface_removed)
 
 	local nth_tick = math.ceil(60/mod_settings.tps);
-	script.on_nth_tick(nil)
-	script.on_nth_tick(nth_tick, on_tick)
+	flib_event.on_nth_tick(nth_tick, on_tick)
 
-	script.on_event(defines.events.on_train_created, on_train_built)
-	script.on_event(defines.events.on_train_changed_state, on_train_changed)
+	flib_event.register(defines.events.on_train_created, on_train_built)
+	flib_event.register(defines.events.on_train_changed_state, on_train_changed)
 
-	script.on_event(defines.events.on_entity_renamed, on_rename)
+	flib_event.register(defines.events.on_entity_renamed, on_rename)
 
 	register_gui_actions()
 end
 
-script.on_load(function()
+flib_event.on_load(function()
 	register_events()
 end)
 
-script.on_init(function()
+flib_event.on_init(function()
 	--TODO: we are not checking changed cargo capacities
 	--find_and_add_all_stations(global)
 	register_events()
 end)
 
-script.on_configuration_changed(function(data)
+flib_event.on_configuration_changed(function(data)
 	--TODO: we are not checking changed cargo capacities
 	--find_and_add_all_stations(global)
 	register_events()