Navigation events

// a navigation event
package
{
    import flash.events.Event;
    public class NavigationEvent extends Event
    {
        public static const RESTART:String = "restart"; // defining a constant for RESTART
        public static const START:String = "start"; // constant for START
        public static const MENUSCREEN:String = "menu"; // constant for MENU

        public function NavigationEvent(type:String)
        {
            super(type);
        }
    }
}

// below is the code for the Game Over screen, the restart button works and calls the navigation event, but the onClickMenu function gives a compiler error "TypeError: Error #1034: Type Coercion failed: cannot convert flash.events::MouseEvent@271aa089 to NavigationEvent."

// Game Over screen class
package
{
    import flash.display.MovieClip;
    import flash.display.SimpleButton;
    import flash.events.MouseEvent;
    import flash.text.TextField;
    import flash.ui.Mouse;

    public class GameOverScreen extends MovieClip
    {
        public function GameOverScreen()
        {
            Mouse.show(); // show mouse cursor
            restartButton.addEventListener( MouseEvent.CLICK, onClickRestart ); // add click listener to button
            menuButton.addEventListener( MouseEvent.CLICK, onClickMenu); // add menu button listener
        }

        public function onClickRestart(mouseEvent:MouseEvent):void // restarts the game when the restart button is clicked!
        {
            dispatchEvent(new NavigationEvent(NavigationEvent.RESTART));
        }

        public function setFinalScore(scoreValue:Number):void // sets the final score display
        {
            finalScore.text = scoreValue.toString();
        }

        public function onClickMenu(navigationEvent:NavigationEvent):void // brings you back to the menu!
        {
            dispatchEvent(new NavigationEvent(NavigationEvent.MENUSCREEN));
        }
    }
}