actionscript 3 - AS3 Error #1010 -

im taking as3 course , on 1 of lessons, on output of program: typeerror: error #1010: term undefined , has no properties. @ main()

this code:

package      {  import flash.display.movieclip; import flash.events.mouseevent;  public class main extends movieclip {      var startpage:startpage;     var hillpage:hillpage;     var lakepage:lakepage;      public function main()     {         startpage = new startpage();         hillpage = new hillpage();         lakepage = new lakepage();         addchild(startpage);          //add event listeners         startpage.hillbutton.addeventlistener(mouseevent.click, onhillbuttonclick);         startpage.pondbutton.addeventlistener(mouseevent.click, onlakebuttonclick);     }     //event handlers     function onhillbuttonclick(event:mouseevent):void     {         addchild(hillpage);         removechild(startpage);     }     function onlakebuttonclick(event:mouseevent):void     {         addchild(lakepage);         removechild(startpage);     }    } } 

if have please post it, driving me crazy.

oh , buttons on file wont work odd reason, same exact code lesson.

thank you

basically means trying access invalid parameter.

most either or both of startpage.hillbutton & startpage.pondbutton not exist. cant perform addeventlistener on items.