ludum-dare-22/objects/obj_menu/KeyPress_13.gml

sound_play(snd_menuselect)
switch menuchoice
   {
   case 0:   //game start
     room_goto(rm_plot)
     break;
   case 1:   //options
     room_goto(rm_options)
     break;
   case 2:   //credits
     room_goto(rm_credits)
     break;
   case 3:   //quit
     game_end()
   default:
     break;
   }