How to use "boolen"?

1

Hi, I m tring to learn how to use a “boolean” in flash so I created a car MC
it moves and hits a wall then I want my car MC to change its direction to another way
and keep moving(say backward)
but it seems there are some mistake to be fixed…
Thanks for any help.


 
onClipEvent(enterFrame)
{
    _root.mcar._x+=3;
    if(_root.mcar.hitTest(_root.wall))
    {
        _root.mcar._rotation+=60;
        dir_back=true;
    }
    if(dir_back)
    {
        _root.mcar._x-=3;
 
        }
 
}