diff --git a/c4mate b/c4mate
index c229b01..7e28490 100755
--- a/c4mate
+++ b/c4mate
@@ -9,14 +9,14 @@
 USER = nil
 HOST = "http://mate.labor.koeln.ccc.de"
 
-function utf8_decode(str)
+local function utf8_decode(str)
     -- Replace JSON Unicode escape sequences with chars.
     if str == nil then return "" end
     return string.gsub(str, "\\u(%x%x%x%x)",
         function (s) return utf8.char(tonumber(s, 16)) end)
 end
 
-function url_encode(str)
+local function url_encode(str)
     -- URL-encode string. Used only for usernames.
     -- Todo: make this more sophisticated.
     return string.gsub(str, " ", "%%20")
@@ -25,10 +25,10 @@ end
 MatePad = {
     CURL_FLAGS = "--silent --show-error --fail --user-agent 'c4mate' --max-redirs 0 --max-filesize 65536",
 }
-function MatePad:new(HOST, USER)
+function MatePad:new(host, user)
     local o = {
-        HOST = HOST,
-        USER = USER,
+        HOST = host,
+        USER = user,
         COOKIE_JAR,
         balance
     }
@@ -199,13 +199,13 @@ function MatePad:print_log(log)
             ))
         elseif event.method == "transferTo" then
             print(string.format(
-                "[%s] Transferred %.2f € to #%d (%s)",
+                "[%s] Transferred %.2f € to user #%d (%s)",
                 event.time, (event.oldbalance - event.newbalance)/100,
                 event.parameter, event.reason
             ))
         elseif event.method == "transferFrom" then
             print(string.format(
-                "[%s] Received %.2f € from #%d (%s)",
+                "[%s] Received %.2f € from user #%d (%s)",
                 event.time, (event.newbalance - event.oldbalance)/100,
                 event.parameter, event.reason
             ))
@@ -306,7 +306,7 @@ Buy by item id (non-interactive):
 Show log:
     c4mate -l|--log
 Add or subtract credits:
-    c4mate <difference>
+    c4mate +/-<amount>
 Give credits:
     c4mate -g <amount> <user> [<reason>]]=])
     os.exit(0)
@@ -327,7 +327,7 @@ if USER == nil then
         os.exit(1)
     end
 end
-pad = MatePad:new(HOST, USER)
+local pad = MatePad:new(HOST, USER)
 
 if arg[1] == nil then
     -- Print balance.
@@ -387,7 +387,7 @@ elseif tonumber(arg[1]) ~= nil then
     -- Add to (or subtract from) balance.
     pad:init()
     if pad:update_balance() then
-        new = math.tointeger(pad.balance + tonumber(arg[1])*100)
+        local new = math.tointeger(pad.balance + tonumber(arg[1])*100)
         if pad:set_balance(new) == "OK" then
             pad:update_balance()
             print(string.format(
@@ -420,7 +420,7 @@ else
     table.sort(menu, function (e1, e2) return e1.id < e2.id end)
 
     -- Check if we can invoke stty.
-    is_tty = os.execute("tty -s") == true
+    local is_tty = os.execute("tty -s") == true
 
     for i, item in ipairs(menu) do
         io.stdout:write(string.format("[%d/%d] Buy %s (#%d) for %.2f €? ",