diff --git a/atm.lua b/atm.lua
index a54f13f..f0b9a5f 100644
--- a/atm.lua
+++ b/atm.lua
@@ -14,8 +14,7 @@ button[1,1;4,1;transaction_log;Transaction Log]
 
 
 local function logout(x,y)
-	return "button[" .. x .. "," .. y ..
-		";2,1;logout;Log Out]"
+	return "button[" .. x .. "," .. y .. ";2,1;logout;Log Out]"
 end
 
 
@@ -41,58 +40,48 @@ end
 
 
 local function new_account_fs(p_name)
-	local fs = "size[4,3]"
-
 	local act_suc, err = exchange:new_account(p_name)
 
+	local fs
 	if not act_suc then
-		fs = fs .. label(0.5,0.5, "Error: " .. err)
+		fs = label(0.5,0.5, "Error: " .. err)
 	else
-		fs = fs .. label(0.5,0.5, "Congratulations on \nyour new account.")
+		fs = label(0.5,0.5, "Congratulations on \nyour new account.")
 	end
 
-	fs = fs .. logout(0.5,2)
-
-	return fs
+	return "size[4,3]" .. fs .. logout(0.5,2)
 end
 
 
 local function info_fs(p_name)
 	local balance = exchange:get_balance(p_name)
 
-	local fs = "size[4,3]"
-
+	local fs
 	if not balance then
-		fs = fs .. label(0.5,0.5, "You don't have an account.")
+		fs = label(0.5,0.5, "You don't have an account.")
 	else
-		fs = fs .. label(0.5,0.5, "Balance: " .. balance)
+		fs = label(0.5,0.5, "Balance: " .. balance)
 	end
 
-	fs = fs .. logout(0.5,2)
-
-	return fs
+	return "size[4,3]" .. fs .. logout(0.5,2)
 end
 
 
 local function wire_fs(p_name)
 	local balance = exchange:get_balance(p_name)
 
-	local fs = "size[4,5]"
-	fs = fs .. logout(0,4)
+	local fs = "size[4,5]" .. logout(0,4)
 
 	if not balance then
-		fs = fs .. label(0.5,0.5, "You don't have an account.")
-		return fs
+		return fs .. label(0.5,0.5, "You don't have an account.")
 	end
 
 	-- To prevent duplicates
-	fs = fs .. field(-100, -100, 0,0, "trans_id", "", unique())
-	fs = fs .. label(0.5,0.5, "Balance: " .. balance)
-	fs = fs .. field(0.5,1.5, 2,1, "recipient", "Send to:", "")
-	fs = fs .. field(0.5,2.5, 2,1, "amount", "Amount", "")
-	fs = fs .. "button[2,4;2,1;send;Send]"
-
-	return fs
+	return fs .. field(-100, -100, 0,0, "trans_id", "", unique()) ..
+		label(0.5,0.5, "Balance: " .. balance) ..
+		field(0.5,1.5, 2,1, "recipient", "Send to:", "") ..
+		field(0.5,2.5, 2,1, "amount", "Amount", "") ..
+		"button[2,4;2,1;send;Send]"
 end
 
 
@@ -102,41 +91,37 @@ local function send_fs(p_name, receiver, amt_str)
 	local amt = tonumber(amt_str)
 
 	if not amt or amt <= 0 then
-		fs = fs .. label(0.5,0.5, "Invalid transfer amount.")
-		fs = fs .. "button[0.5,2;2,1;wire;Back]"
-		
-		return fs
+		return fs .. label(0.5,0.5, "Invalid transfer amount.") ..
+			"button[0.5,2;2,1;wire;Back]"
 	end
-	
+
 	local succ, err = exchange:transfer_credits(p_name, receiver, amt)
 
 	if not succ then
-		fs = fs .. label(0.5,0.5, "Error: " .. err)
-		fs = fs .. "button[0.5,2;2,1;wire;Back]"
-	else
-		fs = fs.. label(0.5,0.5, "Successfully sent "
-					.. amt .. " credits to " .. receiver)
-		fs = fs .. "button[0.5,2;2,1;wire;Back]"
+		return fs .. label(0.5,0.5, "Error: " .. err) ..
+			"button[0.5,2;2,1;wire;Back]"
 	end
-
-	return fs
+	return fs.. label(0.5,0.5, "Successfully sent " ..
+		amt .. " credits to " .. receiver) ..
+		"button[0.5,2;2,1;wire;Back]"
 end
 
 
 local function log_fs(p_name)
-	local res = { "size[8,8]label[0,0;Transaction Log]button[0,7;2,1;logout;Log Out]",
-		      "tablecolumns[text;text]",
-		      "table[0,1;8,6;log_table;Time,Message",
+	local res = {
+		"size[8,8]label[0,0;Transaction Log]button[0,7;2,1;logout;Log Out]",
+		"tablecolumns[text;text]",
+		"table[0,1;8,6;log_table;Time,Message",
 	}
 
-	local log = exchange:player_log(p_name)
-	for i, entry in ipairs(log) do
-		table.insert(res, ",")
-		table.insert(res, tostring(entry.Time))
-		table.insert(res, ",")
-		table.insert(res, entry.Message)
+	for i, entry in ipairs(exchange:player_log(p_name)) do
+		i = i*4
+		res[i] = ","
+		res[i+1] = tostring(entry.Time)
+		res[i+2] = ","
+		res[i+3] = entry.Message
 	end
-	table.insert(res, "]")
+	res[#res+1] ="]"
 
 	return table.concat(res)
 end
@@ -145,9 +130,9 @@ end
 local trans_ids = {}
 
 
-local function handle_fields(player, formname, fields)
+minetest.register_on_player_receive_fields(function(player, formname, fields)
 	if formname ~= atm_form then return end
-	if fields["quit"] then return true end
+	if fields.quit then return true end
 
 	local p_name = player:get_player_name()
 
@@ -159,36 +144,33 @@ local function handle_fields(player, formname, fields)
 
 	trans_ids[p_name] = this_id
 
-	if fields["logout"] then
+	if fields.logout then
 		minetest.show_formspec(p_name, atm_form, main_menu)
 	end
 
-	if fields["new_account"] then
+	if fields.new_account then
 		minetest.show_formspec(p_name, atm_form, new_account_fs(p_name))
 	end
 
-	if fields["info"] then
+	if fields.info then
 		minetest.show_formspec(p_name, atm_form, info_fs(p_name))
 	end
 
-	if fields["wire"] then
+	if fields.wire then
 		minetest.show_formspec(p_name, atm_form, wire_fs(p_name))
 	end
 
-	if fields["send"] then
+	if fields.send then
 		minetest.show_formspec(p_name, atm_form,
 				       send_fs(p_name, fields.recipient, fields.amount))
 	end
 
-	if fields["transaction_log"] then
+	if fields.transaction_log then
 		minetest.show_formspec(p_name, atm_form, log_fs(p_name))
 	end
 
 	return true
-end
-
-
-minetest.register_on_player_receive_fields(handle_fields)
+end)
 
 
 minetest.register_node("global_exchange:atm", {
@@ -198,10 +180,8 @@ minetest.register_node("global_exchange:atm", {
 		 "global_exchange_atm_side.png",
 	},
 	groups = {cracky=2},
-	on_rightclick = function(pos, node, clicker)
-		local p_name = clicker:get_player_name()
-
-		minetest.show_formspec(p_name, atm_form, main_menu)
+	on_rightclick = function(pos, _, clicker)
+		minetest.show_formspec(clicker:get_player_name(), atm_form, main_menu)
 	end,
 })
 
diff --git a/digital_mailbox.lua b/digital_mailbox.lua
index 0697d78..96107f0 100644
--- a/digital_mailbox.lua
+++ b/digital_mailbox.lua
@@ -19,37 +19,37 @@ end
 
 
 local function mk_inbox_list(results, x, y, w, h)
-	local res = {}
-	table.insert(res, "textlist[")
-	table.insert(res, tostring(x))
-	table.insert(res, ",")
-	table.insert(res, tostring(y))
-	table.insert(res, ";")
-	table.insert(res, tostring(w))
-	table.insert(res, ",")
-	table.insert(res, tostring(h))
-	table.insert(res, ";result_list;")
+	local res = {
+		"textlist[",
+		tostring(x),
+		",",
+		tostring(y),
+		";",
+		tostring(w),
+		",",
+		tostring(h),
+		";result_list;"
+	}
 
 	for i, row in ipairs(results) do
-		table.insert(res, row.Amount .. " " .. row.Item)
-		table.insert(res, ",")
+		res[i*2+8] = row.Amount .. " " .. row.Item
+		res[i*2+9] = ","
 	end
-	table.insert(res, "]")
+	res[#res+1] = "]"
 
 	return table.concat(res)
 end
 
 
 local function mk_mail_fs(p_name, results, err_str)
-	fs = "size[6,8]"
-	fs = fs .. "label[0,0;Inbox]"
+	fs = "size[6,8]" ..
+		"label[0,0;Inbox]"
 	if err_str then
 		fs = fs .. "label[3,0;Error: " .. err_str .. "]"
 	end
-	fs = fs .. mk_inbox_list(results, 0, 1, 6, 6)
-	fs = fs .. "button[0,7;2,1;claim;Claim]"
 
-	return fs
+	return fs .. mk_inbox_list(results, 0, 1, 6, 6) ..
+		"button[0,7;2,1;claim;Claim]"
 end
 
 
@@ -58,14 +58,15 @@ local function show_mail(p_name, results, err_str)
 end
 
 
-local function handle_fields(player, formname, fields)
+minetest.register_on_player_receive_fields(function(player, formname, fields)
 	if formname ~= mailbox_form then return end
-	if fields["quit"] then return true end
+	if fields.quit then return true end
 
 	local p_name = player:get_player_name()
 	local idx = selected_index[p_name]
 
-	if fields["claim"] and idx then
+	if fields.claim
+	and idx then
 		local row = get_mail(p_name)[idx]
 
 		if row then
@@ -77,7 +78,7 @@ local function handle_fields(player, formname, fields)
 				show_mail(p_name, get_mail(p_name), "Not enough room.")
 				return true
 			end
-			
+
 			local succ, res = exchange:take_inbox(row.Id, row.Amount)
 			if not succ then
 				show_mail(p_name, get_mail(p_name), res)
@@ -92,8 +93,8 @@ local function handle_fields(player, formname, fields)
 		end
 	end
 
-	if fields["result_list"] then
-		local event = minetest.explode_textlist_event(fields["result_list"])
+	if fields.result_list then
+		local event = minetest.explode_textlist_event(fields.result_list)
 
 		if event.type == "CHG" then
 			selected_index[p_name] = event.index
@@ -101,10 +102,7 @@ local function handle_fields(player, formname, fields)
 	end
 
 	return true
-end
-
-
-minetest.register_on_player_receive_fields(handle_fields)
+end)
 
 
 minetest.register_node("global_exchange:mailbox", {
@@ -116,7 +114,7 @@ minetest.register_node("global_exchange:mailbox", {
 	groups = {cracky=2},
 	on_rightclick = function(pos, node, clicker)
 		local p_name = clicker:get_player_name()
-		local succ, res = exchange:view_inbox(p_name)
+		local _,res = exchange:view_inbox(p_name)
 		mailbox_contents[p_name] = res
 		minetest.show_formspec(p_name, mailbox_form, mk_mail_fs(p_name, res))
 	end,
diff --git a/exchange.lua b/exchange.lua
index 904332d..e23d488 100644
--- a/exchange.lua
+++ b/exchange.lua
@@ -77,7 +77,7 @@ SELECT
     AND Orders.Type = "sell"
   )
 FROM distinct_items;
-    
+
 
 END TRANSACTION;
 ]=]
@@ -239,7 +239,7 @@ end
 
 
 local function is_integer(num)
-	return math.floor(num) == num
+	return num%1 == 0
 end
 
 
@@ -248,7 +248,7 @@ local function exec_stmt(db, stmt, names)
 
 	local res = stmt:step()
 	stmt:reset()
-	
+
 	if res == sqlite3.BUSY then
 		return false, "Database Busy."
 	elseif res ~= sqlite3.DONE then
@@ -292,7 +292,7 @@ function exports.open_exchange(path)
 		transaction_log_stmt = assert(db:prepare(transaction_log_query)),
 	}
 
-	
+
 	local ret = { db = db,
 		      stmts = stmts,
 	}
@@ -332,7 +332,7 @@ function ex_methods.log(self, message, recipient)
 		return true
 	end
 end
-		
+
 
 -- Returns success boolean and error.
 function ex_methods.new_account(self, p_name, amt)
@@ -346,7 +346,7 @@ function ex_methods.new_account(self, p_name, amt)
 	end
 
 	db:exec("BEGIN TRANSACTION;")
-	
+
 	local stmt = self.stmts.new_act_stmt
 
 	stmt:bind_names({
@@ -385,7 +385,7 @@ function ex_methods.new_account(self, p_name, amt)
 	end
 
 	db:exec("COMMIT;")
-	
+
 	return true
 end
 
@@ -394,7 +394,7 @@ end
 function ex_methods.get_balance(self, p_name)
 	local db = self.db
 	local stmt = self.stmts.get_balance_stmt
-	
+
 	stmt:bind_values(p_name)
 	local res = stmt:step()
 
@@ -534,11 +534,6 @@ end
 
 -- Returns a list of orders, sorted by price.
 function ex_methods.search_orders(self, ex_name, order_type, item_name)
-	local params = { ex_name = ex_name,
-			 order_type = order_type,
-			 item_name = item_name,
-	}
-
 	local stmt
 	if order_type == "buy" then
 		stmt = self.stmts.search_asc_stmt
@@ -546,12 +541,17 @@ function ex_methods.search_orders(self, ex_name, order_type, item_name)
 		stmt = self.stmts.search_desc_stmt
 	end
 
-	stmt:bind_names(params)
+	stmt:bind_names({
+		ex_name = ex_name,
+		order_type = order_type,
+		item_name = item_name,
+	})
 
-	local orders = {}
+	local orders,n = {},1
 
 	for tab in stmt:nrows() do
-		table.insert(orders, tab)
+		orders[n] = tab
+		n = n+1
 	end
 
 	stmt:reset()
@@ -561,17 +561,15 @@ end
 
 -- Same as above, except not sorted in any particular order.
 function ex_methods.search_player_orders(self, p_name)
-	local params = { p_name = p_name,
-	}
-
 	local stmt = self.stmts.search_own_stmt
 
-	stmt:bind_names(params)
+	stmt:bind_names({p_name = p_name})
 
-	local orders = {}
+	local orders,n = {},1
 
 	for tab in stmt:nrows() do
-		table.insert(orders, tab)
+		orders[n] = tab
+		n = n+1
 	end
 
 	stmt:reset()
@@ -692,31 +690,31 @@ end
 -- remaining desired amount. Returns success. If succeeded, also returns amount
 -- bought. If failed, returns an error message
 function ex_methods.buy(self, p_name, ex_name, item_name, amount, rate)
-	if math.floor(amount) ~= amount then
+	if not is_integer(amount) then
 		return false, "Noninteger quantity"
 	elseif amount <= 0 then
 		return false, "Nonpositive quantity"
-	elseif math.floor(rate) ~= rate then
+	elseif not is_integer(rate) then
 		return false, "Noninteger rate"
 	elseif rate <= 0 then
 		return false, "Nonpositive rate"
 	end
 
 	local db = self.db
-	
+
 	local bal = self:get_balance(p_name)
 
 	if not bal then
 		return false, "Nonexistent account."
 	end
-	
+
 	if bal < amount * rate then
 		return false, "Not enough money."
 	end
-	
+
 
 	db:exec("BEGIN TRANSACTION");
-	
+
 	local remaining = amount
 
 	local del_stmt = self.stmts.del_order_stmt
@@ -748,7 +746,7 @@ function ex_methods.buy(self, p_name, ex_name, item_name, amount, rate)
 			end
 			del_stmt:reset()
 
-			local ch_succ, ch_err = 
+			local ch_succ, ch_err =
 				self:change_balance(poster, rate * row_amount)
 			if not ch_succ then
 				search_stmt:reset()
@@ -756,7 +754,7 @@ function ex_methods.buy(self, p_name, ex_name, item_name, amount, rate)
 				return false, ch_err
 			end
 
-			local log_succ, log_err = 
+			local log_succ, log_err =
 				self:log(p_name .. " bought " .. row_amount .. " "
 						 .. item_name .. " from you. (+"
 						 .. rate * row_amount .. ")", poster)
@@ -793,7 +791,7 @@ function ex_methods.buy(self, p_name, ex_name, item_name, amount, rate)
 			end
 			red_stmt:reset()
 
-			local ch_succ, ch_err = 
+			local ch_succ, ch_err =
 				self:change_balance(poster, rate * remaining)
 			if not ch_succ then
 				search_stmt:reset()
@@ -801,7 +799,7 @@ function ex_methods.buy(self, p_name, ex_name, item_name, amount, rate)
 				return false, ch_err
 			end
 
-			local log_succ, log_err = 
+			local log_succ, log_err =
 				self:log(p_name .. " bought " .. remaining .. " "
 						 .. item_name .. " from you. (+"
 						 .. rate * remaining .. ")", poster)
@@ -867,20 +865,20 @@ end
 -- Tries to sell to orders at the provided rate, and posts an offer with any
 -- remaining desired amount. Returns success. If failed, returns an error message.
 function ex_methods.sell(self, p_name, ex_name, item_name, amount, rate)
-	if math.floor(amount) ~= amount then
+	if not is_integer(amount) then
 		return false, "Noninteger quantity"
 	elseif amount <= 0 then
 		return false, "Nonpositive quantity"
-	elseif math.floor(rate) ~= rate then
+	elseif not is_integer(rate) then
 		return false, "Noninteger rate"
 	elseif rate <= 0 then
 		return false, "Nonpositive rate"
 	end
 
 	local db = self.db
-	
+
 	db:exec("BEGIN TRANSACTION");
-	
+
 	local remaining = amount
 	local revenue = 0
 
@@ -913,7 +911,7 @@ function ex_methods.sell(self, p_name, ex_name, item_name, amount, rate)
 			end
 			del_stmt:reset()
 
-			local in_succ, in_err = 
+			local in_succ, in_err =
 				self:put_in_inbox(poster, item_name, row_amount)
 			if not in_succ then
 				search_stmt:reset()
@@ -921,7 +919,7 @@ function ex_methods.sell(self, p_name, ex_name, item_name, amount, rate)
 				return false, in_err
 			end
 
-			local log_succ, log_err = 
+			local log_succ, log_err =
 				self:log(p_name .. " sold " .. row_amount .. " "
 						 .. item_name .. " to you." , poster)
 			if not log_succ then
@@ -958,7 +956,7 @@ function ex_methods.sell(self, p_name, ex_name, item_name, amount, rate)
 			end
 			red_stmt:reset()
 
-			local in_succ, in_err = 
+			local in_succ, in_err =
 				self:put_in_inbox(poster, item_name, remaining)
 			if not in_succ then
 				search_stmt:reset()
@@ -966,7 +964,7 @@ function ex_methods.sell(self, p_name, ex_name, item_name, amount, rate)
 				return false, in_err
 			end
 
-			local log_succ, log_err = 
+			local log_succ, log_err =
 				self:log(p_name .. " sold " .. remaining .. " "
 						 .. item_name .. " to you.", poster)
 			if not log_succ then
@@ -986,7 +984,6 @@ function ex_methods.sell(self, p_name, ex_name, item_name, amount, rate)
 			end
 
 			remaining = 0
-			revenue = revenue + remaining * row.Rate
 		end
 
 		if remaining == 0 then break end
@@ -1018,17 +1015,17 @@ end
 
 
 -- On success, returns true and a list of inbox entries.
--- On failure, returns false and an error message.
+-- TODO: On failure, return false and an error message.
 function ex_methods.view_inbox(self, p_name)
-	local db = self.db
 	local stmt = self.stmts.view_inbox_stmt
 
 	stmt:bind_values(p_name)
 
-	local res = {}
+	local res,n = {},1
 
 	for row in stmt:nrows() do
-		table.insert(res, row)
+		res[n] = row
+		n = n+1
 	end
 
 	stmt:reset()
@@ -1049,7 +1046,7 @@ function ex_methods.take_inbox(self, id, amount)
 		id = id,
 		change = amount
 	})
-	
+
 	local res = get_stmt:step()
 
 	if res == sqlite3.BUSY then
@@ -1066,7 +1063,7 @@ function ex_methods.take_inbox(self, id, amount)
 	get_stmt:reset()
 
 	db:exec("BEGIN TRANSACTION;")
-	
+
 	if available > amount then
 		red_stmt:bind_names({
 			id = id,
@@ -1115,18 +1112,18 @@ end
 --   sell_volume: Number of items for sale
 --   sell_min: Minimum sell rate
 function ex_methods.market_summary(self)
-	local db = self.db
 	local stmt = self.stmts.summary_stmt
 
-	local res = {}
+	local res,n = {},1
 	for a in stmt:rows() do
-		table.insert(res, {
+		res[n] = {
 			item_name = a[1],
 			buy_volume = a[2],
 			buy_max = a[3],
 			sell_volume = a[4],
 			sell_min = a[5],
-		})
+		}
+		n = n+1
 	end
 	stmt:reset()
 
@@ -1138,11 +1135,12 @@ end
 function ex_methods.player_log(self, p_name)
 	local stmt = self.stmts.transaction_log_stmt
 	stmt:bind_names({ p_name = p_name })
-	
-	local res = {}
+
+	local res,n = {},1
 
 	for row in stmt:nrows() do
-		table.insert(res, row)
+		res[n] = row
+		n = n+1
 	end
 
 	stmt:reset()
@@ -1162,7 +1160,7 @@ function exports.test()
 		print("Bob: ", ex:get_balance("Bob"))
 	end
 
-	
+
 	-- Initialize balances
 	if alice_bal then
 		ex:set_balance("Alice", 420)
@@ -1178,7 +1176,7 @@ function exports.test()
 
 	print_balances()
 
-	
+
 	-- Transfer a valid amount
 	print("Transfering 1000 credits from Bob to Alice")
 
@@ -1207,7 +1205,7 @@ function exports.test()
 	local succ, err = ex:sell("Bob", "", "default:cobble", 20, 1)
 	print("Success: ", succ, " ", err)
 	print_balances()
-	
+
 	ex:close()
 end
 
diff --git a/exchange_machine.lua b/exchange_machine.lua
index d071e38..17d2fee 100644
--- a/exchange_machine.lua
+++ b/exchange_machine.lua
@@ -3,46 +3,41 @@ local exchange = ...
 local search_cooldown = 2
 local summary_interval = 600
 
+local summary_fs = ""
 local function mk_summary_fs()
-	local summary = exchange:market_summary()
-	local res = {}
-	table.insert(res, "size[8,8]")
-	table.insert(res, "label[0,0;Updated Periodically]")
-	table.insert(res, "tablecolumns[text;text;text;text;text;text]")
-	table.insert(res, "table[0,1;8,6;summary_table;")
-	table.insert(res, "Item,Description,Buy Vol,Buy Max,Sell Vol,Sell Min")
+	local res = {
+		"size[8,8]",
+		"label[0,0;Updated Periodically]",
+		"tablecolumns[text;text;text;text;text;text]",
+		"table[0,1;8,6;summary_table;",
+		"Item,Description,Buy Vol,Buy Max,Sell Vol,Sell Min"
+	}
 
 	local all_items = minetest.registered_items
-	for i, row in ipairs(summary) do
-		table.insert(res, "," .. row.item_name)
-		local def = all_items[row.item_name]
-		if def then
-			table.insert(res, "," .. def.description)
-		else
-			table.insert(res, "," .. "Unknown Item")
-		end
-		table.insert(res, "," .. (row.buy_volume or 0))
-		table.insert(res, "," .. (row.buy_max or "N/A"))
-		table.insert(res, "," .. (row.sell_volume or 0))
-		table.insert(res, "," .. (row.sell_min or "N/A"))
+	for i, row in ipairs(exchange:market_summary()) do
+		local n = #res+1
+		res[n] = "," .. row.item_name
+		local def = all_items[row.item_name] or {}
+		res[n+1] = "," .. (def.description or "Unknown Item")
+		res[n+2] = "," .. (row.buy_volume or 0)
+		res[n+3] = "," .. (row.buy_max or "N/A")
+		res[n+4] = "," .. (row.sell_volume or 0)
+		res[n+5] = "," .. (row.sell_min or "N/A")
 	end
 
-	table.insert(res, "]")
-	table.insert(res, "button[3,7;2,1;back;Back]")
-	
-	return table.concat(res)
+	res[#res+1] = "]"
+	res[#res+1] = "button[3,7;2,1;back;Back]"
+
+	summary_fs = table.concat(res)
 end
-local summary_fs = ""
-minetest.after(0, function()
-	summary_fs = mk_summary_fs()
-end)
+minetest.after(0, mk_summary_fs)
 
 
 local elapsed = 0
 minetest.register_globalstep(function(dtime)
 	elapsed = elapsed + dtime
 	if elapsed >= summary_interval then
-		summary_fs = mk_summary_fs()
+		mk_summary_fs()
 		elapsed = 0
 	end
 end)
@@ -61,17 +56,12 @@ local main_state = {}
 --                       a cooldown on searches
 --     sell: A boolean whether the player has sell selected
 
-
-local function default_main_state()
-	return { old_fields = {},
-		 search_results = {},
-		 last_search_time = 0,
-	}
-end
-
-
 minetest.register_on_joinplayer(function(player)
-	main_state[player:get_player_name()] = default_main_state()
+	main_state[player:get_player_name()] = {
+		old_fields = {},
+		search_results = {},
+		last_search_time = 0,
+	}
 end)
 
 minetest.register_on_leaveplayer(function(player)
@@ -87,16 +77,18 @@ local tablecolumns =
 
 
 local function table_from_results(results, x, y, w, h, selected)
-	local fs_tab = {}
+	local fs_tab
 
 	local function insert(str)
-		table.insert(fs_tab, str)
+		fs_tab[#fs_tab+1] = str
 	end
 
-	insert(tablecolumns)
-	insert("table[" .. x .. "," .. y .. ";" .. w .. "," .. h .. ";")
-	insert("result_table;")
-	insert("Poster,Type,Item,Description,Amount,Rate")
+	fs_tab = {
+		tablecolumns,
+		"table[" .. x .. "," .. y .. ";" .. w .. "," .. h .. ";",
+		"result_table;",
+		"Poster,Type,Item,Description,Amount,Rate"
+	}
 
 	local all_items = minetest.registered_items
 
@@ -108,11 +100,8 @@ local function table_from_results(results, x, y, w, h, selected)
 		insert(",")
 		insert(tostring(row.Item))
 		insert(",")
-		if all_items[row.Item] then
-			insert(all_items[row.Item].description)
-		else
-			insert("Unknown Item")
-		end
+		local def = all_items[row.Item] or {}
+		insert(def.description or "Unknown Item")
 		insert(",")
 		insert(tostring(row.Amount))
 		insert(",")
@@ -130,8 +119,6 @@ end
 
 
 local function mk_main_fs(p_name, new_item, err_str, success)
-	local fs = "size[8,9]"
-
 	local state = main_state[p_name]
 	if not state then return end -- Should have been initialized on player join
 
@@ -145,21 +132,22 @@ local function mk_main_fs(p_name, new_item, err_str, success)
 
 	local bal = exchange:get_balance(p_name)
 
+	local fs
 	if bal then
-		fs = fs .. "label[0,0;Balance: " .. bal .. "]"
+		fs = "label[0,0;Balance: " .. bal .. "]"
 	else
-		fs = fs .. "label[0.2,0.5;Use an ATM to make your account.]"
+		fs = "label[0.2,0.5;Use an ATM to make your account.]"
 	end
 
-	fs = fs .. "button[4,0;2,1;summary;Market Summary]"
-	fs = fs .. "button[6,0;2,1;your_orders;Your Orders]"
-	fs = fs .. "field[0.2,1.5;3,1;item;Item: ;" .. item_def .. "]"
-	fs = fs .. "field[3.2,1.5;3,1;amount;Amount: ;" .. amount_def .. "]"
-	fs = fs .. "button[6,1;2,1.4;select_item;Select Item]"
-	fs = fs .. "checkbox[5,3;sell;Sell;" .. tostring(sell_def) .. "]"
-	fs = fs .. "field[0.2,2.5;2,1;rate;Rate: ;" .. rate_def .. "]"
-	fs = fs .. "button[2,2;2,1.4;search;Search]"
-	fs = fs .. "button[4,2;3,1.4;post_order;Post Order]"
+	fs = fs .. "button[4,0;2,1;summary;Market Summary]" ..
+		"button[6,0;2,1;your_orders;Your Orders]" ..
+		"field[0.2,1.5;3,1;item;Item: ;" .. item_def .. "]" ..
+		"field[3.2,1.5;3,1;amount;Amount: ;" .. amount_def .. "]" ..
+		"button[6,1;2,1.4;select_item;Select Item]" ..
+		"checkbox[5,3;sell;Sell;" .. tostring(sell_def) .. "]" ..
+		"field[0.2,2.5;2,1;rate;Rate: ;" .. rate_def .. "]" ..
+		"button[2,2;2,1.4;search;Search]" ..
+		"button[4,2;3,1.4;post_order;Post Order]"
 
 	if err_str then
 		fs = fs .. "label[0,3;Error: " .. err_str .. "]"
@@ -169,9 +157,7 @@ local function mk_main_fs(p_name, new_item, err_str, success)
 		fs = fs .. "label[0,3;Success!]"
 	end
 
-	fs = fs .. table_from_results(results, 0, 4, 8, 5, selected_def)
-
-	return fs
+	return "size[8,9]" .. fs .. table_from_results(results, 0, 4, 8, 5, selected_def)
 end
 
 
@@ -181,15 +167,16 @@ end
 
 
 -- Something similar to creative inventory
-local selectable_inventory_size = 0
+local pagemax = 1
 
 -- Create detached inventory after loading all mods
 minetest.after(0, function()
 	local inv = minetest.create_detached_inventory("global_exchange", {
-		allow_move = function(inv, from_list, from_index, to_list, to_index, count, player)
+		allow_move = function(inv, from_list, _, to_list, _,_, player)
 			local p_name = player:get_player_name()
 
-			if from_list == "main" and to_list == "p_" .. p_name then
+			if from_list == "main"
+			and to_list == "p_" .. p_name then
 				return 1
 			else
 				return 0
@@ -201,7 +188,7 @@ minetest.after(0, function()
 		allow_take = function()
 			return 0
 		end,
-		on_move = function(inv, from_list, from_index, to_list, to_index, count, player)
+		on_move = function(inv, _, _, _, _, _, player)
 			local p_name = player:get_player_name()
 			local p_list = "p_" .. p_name
 
@@ -212,11 +199,14 @@ minetest.after(0, function()
 		end,
 	})
 
-	local selectable_list = {}
+	local selectable_list,n = {},1
 	for name, def in pairs(minetest.registered_items) do
-		if (not def.groups.not_in_creative_inventory or def.groups.not_in_creative_inventory == 0)
-		and def.description and def.description ~= "" then
-			table.insert(selectable_list, name)
+		if (not def.groups.not_in_creative_inventory
+			or def.groups.not_in_creative_inventory == 0)
+		and def.description
+		and def.description ~= "" then
+			selectable_list[n] = name
+			n = n+1
 		end
 	end
 	table.sort(selectable_list)
@@ -225,32 +215,29 @@ minetest.after(0, function()
 		inv:add_item("main", ItemStack(itemstring))
 	end
 
-	selectable_inventory_size = #selectable_list
+	pagemax = math.ceil((#selectable_list - 1) / (8 * 4))
 end)
 
 
 minetest.register_on_joinplayer(function(player)
-	local big_inv = minetest.get_inventory({type="detached", name="global_exchange"})
-	local p_list = "p_" .. player:get_player_name()
-
-	big_inv:set_size(p_list, 1)
+	-- the inventory list name is "p_"..player_name
+	minetest.get_inventory({
+		type="detached",
+		name="global_exchange"
+	}):set_size("p_" .. player:get_player_name(), 1)
 end)
-	
+
 
 local select_form = "global_exchange:select_form"
 
 
 local function mk_select_formspec(p_name, start_i, pagenum)
-	pagenum = math.floor(pagenum)
-	local pagemax = math.floor((selectable_inventory_size - 1) / (8 * 4) + 1)
-	local p_list = "p_" .. p_name
-
 	return "size[9.3,8]" ..
 		"list[detached:global_exchange;main;0.3,0.5;8,4;" .. tostring(start_i) .. "]" ..
 		"button[0.3,4.5;1.6,1;select_prev;<<]"..
 		"button[6.7,4.5;1.6,1;select_next;>>]"..
-		"label[2.0,5.55;"..tostring(pagenum).."/"..tostring(pagemax).."]"..
-		"list[detached:global_exchange;" .. p_list .. ";0.3,7;1,1;]"
+		"label[2.0,5.55;"..tostring(math.floor(pagenum)).."/"..tostring(pagemax).."]"..
+		"list[detached:global_exchange;p_" .. p_name .. ";0.3,7;1,1;]"
 end
 
 
@@ -274,17 +261,12 @@ local own_state = {}
 --     own_results: Results for own orders.
 
 local function mk_own_orders_fs(p_name, results, selected)
-	local fs = "size[8,8]"
-	
-	local state = main_state[p_name]
-
-	fs = fs .. "label[0.5,0.2;Your Orders]"
-	fs = fs .. "button[6,0;2,1;refresh;Refresh]"
-	fs = fs .. table_from_results(results, 0, 2, 8, 4.5, selected or "")
-	fs = fs .. "button[0,7;2,1;cancel;Cancel]"
-	fs = fs .. "button[3,7;2,1;back;Back]"
-
-	return fs
+	return "size[8,8]" ..
+		"label[0.5,0.2;Your Orders]" ..
+		"button[6,0;2,1;refresh;Refresh]" ..
+		table_from_results(results, 0, 2, 8, 4.5, selected or "") ..
+		"button[0,7;2,1;cancel;Cancel]" ..
+		"button[3,7;2,1;back;Back]"
 end
 
 
@@ -296,11 +278,11 @@ end
 -- Returns success, and also returns an error message if failed.
 local function post_order(player, ex_name, order_type, item_name, amount_str, rate_str)
 	local p_name = player:get_player_name()
-	
+
 	if item_name == "" then
 		return false, "You must input an item"
 	end
-	
+
 	if not minetest.registered_items[item_name] then
 		return false, "That item does not exist."
 	end
@@ -323,7 +305,7 @@ local function post_order(player, ex_name, order_type, item_name, amount_str, ra
 	local p_inv = player:get_inventory()
 	local stack = ItemStack(item_name)
 	stack:set_count(amount)
-	
+
 	if order_type == "buy" then
 		if not p_inv:room_for_item("main", stack) then
 			return false, "Not enough space in inventory."
@@ -353,8 +335,7 @@ local function post_order(player, ex_name, order_type, item_name, amount_str, ra
 end
 
 
-local function handle_main(player, formname, fields)
-	if formname ~= main_form then return end
+local function handle_main(player, fields)
 	local p_name = player:get_player_name()
 	local state = main_state[p_name]
 	local old_fields = state.old_fields
@@ -363,17 +344,17 @@ local function handle_main(player, formname, fields)
 		old_fields[k] = v
 	end
 
-	if fields["select_item"] then
+	if fields.select_item then
 		show_select(p_name)
 	end
 
-	if fields["search"] then
+	if fields.search then
 		local now = os.time()
 		local last_search = state.last_search_time
 
 		if now - last_search < search_cooldown then
 			show_main(p_name, nil, "Please wait before searching again.")
-			return true
+			return
 		end
 
 		-- If the player is selling, she wants "buy" type offers.
@@ -392,22 +373,18 @@ local function handle_main(player, formname, fields)
 		show_main(p_name)
 	end
 
-	if fields["sell"] then
-		if fields["sell"] == "true" then
-			state.sell = true
-		else
-			state.sell = false
-		end
+	if fields.sell then
+		state.sell = fields.sell == "true"
 	end
-	
 
-	if fields["post_order"] then
+
+	if fields.post_order then
 		local now = os.time()
 		local last_search = state.last_search_time
 
 		if now - last_search < search_cooldown then
 			show_main(p_name, nil, "Please wait before posting.")
-			return true
+			return
 		end
 
 		local order_type
@@ -416,12 +393,9 @@ local function handle_main(player, formname, fields)
 		else
 			order_type = "buy"
 		end
-		local item_name = fields["item"]
-		local amount_str = fields["amount"]
-		local rate_str = fields["rate"]
 
 		local succ, err =
-			post_order(player, "", order_type, item_name, amount_str, rate_str)
+			post_order(player, "", order_type, fields.item, fields.amount, fields.rate)
 
 		if succ then
 			state.search_results = {}
@@ -432,17 +406,17 @@ local function handle_main(player, formname, fields)
 	end
 
 
-	if fields["result_table"] then
+	if fields.result_table then
 		local results = state.search_results
-		local event = minetest.explode_table_event(fields["result_table"])
+		local event = minetest.explode_table_event(fields.result_table)
 
 		if event.type ~= "CHG" then
-			return true
+			return
 		end
 
 		local index = event.row - 1
 		result = results[index]
-		
+
 		if result then
 			old_fields.amount = tostring(result.Amount)
 			old_fields.rate = tostring(result.Rate)
@@ -451,11 +425,11 @@ local function handle_main(player, formname, fields)
 		show_main(p_name)
 	end
 
-	if fields["summary"] then
+	if fields.summary then
 		show_summary(p_name)
 	end
 
-	if fields["your_orders"] then
+	if fields.your_orders then
 		if not own_state[p_name] then
 			own_state[p_name] = {}
 		end
@@ -465,46 +439,37 @@ local function handle_main(player, formname, fields)
 
 		show_own_orders(p_name, o_state.own_results)
 	end
-
-	return true
 end
 
 
-local function handle_select(player, formname, fields)
-	if formname ~= select_form then return end
-
+local function handle_select(player, fields)
 	local p_name = player:get_player_name()
-	
-	local pagemax = math.floor((selectable_inventory_size - 1) / (8 * 4) + 1)
+
 	local pagenum = player_pages[p_name] or 1
 
-	if fields["select_prev"] then
+	if fields.select_prev then
 		player_pages[p_name] = math.max(1, pagenum - 1)
 		show_select(p_name)
-	elseif fields["select_next"] then
+	elseif fields.select_next then
 		player_pages[p_name] = math.min(pagemax, pagenum + 1)
 		show_select(p_name)
 	end
-
-	return true
 end
 
 
-local function handle_own_orders(player, formname, fields)
-	if formname ~= own_form then return end
-
+local function handle_own_orders(player, fields)
 	local p_name = player:get_player_name()
 
 	local state = own_state[p_name] or {}
 	local results = state.own_results or {}
 	local idx = state.selected_index
 
-	if fields["refresh"] then
+	if fields.refresh then
 		state.own_results = exchange:search_player_orders(p_name) or {}
 		show_own_orders(p_name, state.own_results)
 	end
 
-	if fields["cancel"] and idx then
+	if fields.cancel and idx then
 		local row = results[idx]
 		if not row then return true end
 		local p_inv = player:get_inventory()
@@ -535,39 +500,41 @@ local function handle_own_orders(player, formname, fields)
 		show_own_orders(p_name, state.own_results)
 	end
 
-	if fields["result_table"] then
-		local event = minetest.explode_table_event(fields["result_table"])
+	if fields.result_table then
+		local event = minetest.explode_table_event(fields.result_table)
 		if event.type == "CHG" then
 			state.selected_index = event.row - 1
 			show_own_orders(p_name, results, event.row)
 		end
 	end
 
-	if fields["back"] then
+	if fields.back then
 		show_main(p_name)
 	end
-
-	return true
 end
 
 
-local function handle_summary(player, formname, fields)
-	if formname ~= summary_form then return end
-
-	local p_name = player:get_player_name()
-
-	if fields["back"] then
-		show_main(p_name)
+local function handle_summary(player, fields)
+	if fields.back then
+		show_main(player:get_player_name())
 	end
-
-	return true
 end
 
 
-minetest.register_on_player_receive_fields(handle_main)
-minetest.register_on_player_receive_fields(handle_select)
-minetest.register_on_player_receive_fields(handle_own_orders)
-minetest.register_on_player_receive_fields(handle_summary)
+minetest.register_on_player_receive_fields(function(player, formname, fields)
+	if formname == main_form then
+		handle_main(player, fields)
+	elseif formname == select_form then
+		handle_select(player, fields)
+	elseif formname == own_form then
+		handle_own_orders(player, fields)
+	elseif formname == summary_form then
+		handle_summary(player, fields)
+	else
+		return
+	end
+	return true
+end)
 
 
 minetest.register_node("global_exchange:exchange", {
@@ -577,7 +544,7 @@ minetest.register_node("global_exchange:exchange", {
 		 "global_exchange_exchange_side.png",
 	},
 	groups = {cracky=2},
-	on_rightclick = function(pos, node, clicker)
+	on_rightclick = function(_, _, clicker)
 		local p_name = clicker:get_player_name()
 		local state = main_state[p_name]
 		if state then
diff --git a/init.lua b/init.lua
index 158b4f6..aed516b 100644
--- a/init.lua
+++ b/init.lua
@@ -1,9 +1,7 @@
 
 local modpath = minetest.get_modpath(minetest.get_current_modname()) .. "/"
-local savepath = minetest.get_worldpath() .. "/global_exchange.db"
 
-local income_str = minetest.setting_get("citizens_income")
-local income = income_str and tonumber(income_str) or 10
+local income = tonumber(minetest.setting_get("citizens_income")) or 10
 
 local income_interval = 1200
 
@@ -11,41 +9,40 @@ local income_msg = "You receive your citizen's income (+" .. income .. ")"
 
 local next_payout = os.time() + income_interval
 
-local ex = dofile(modpath .. "exchange.lua")
-local exchange = ex.open_exchange(savepath)
+local exchange = (dofile(modpath .. "exchange.lua")).open_exchange(
+	minetest.get_worldpath() .. "/global_exchange.db"
+)
 
 
 minetest.register_on_shutdown(function()
-		exchange:close()
+	exchange:close()
 end)
 
 
--- Only check once in a while
-local elapsed = 0
+local function check_giving()
+	local now = os.time()
+	if now < next_payout then
+		return
+	end
 
-minetest.register_globalstep(function(dtime)
-		elapsed = elapsed + dtime
-		if elapsed <= 5 then return end
+	next_payout = now + income_interval
 
-		elapsed = 0
+	for _, player in ipairs(minetest.get_connected_players()) do
+		local p_name = player:get_player_name()
 
-		local now = os.time()
-		if now < next_payout then return end
+		local succ = exchange:give_credits(p_name, income,
+			"Citizen's Income (+" .. income .. ")")
 
-		next_payout = now + income_interval
-
-		for i, player in ipairs(minetest.get_connected_players()) do
-			local p_name = player:get_player_name()
-
-			local succ =
-				exchange:give_credits(p_name, income,
-						      "Citizen's Income (+" .. income .. ")")
-
-			if succ then
-				minetest.chat_send_player(p_name, income_msg)
-			end
+		if succ then
+			minetest.chat_send_player(p_name, income_msg)
 		end
-end)
+	end
+
+	minetest.after(5, check_giving)
+end
+
+minetest.after(5, check_giving)
+
 
 
 assert(loadfile(modpath .. "atm.lua"))(exchange)