Unable to assign buttons to move my character

1

I am trying to assign buttons my on my ‘gameScreen’ to move my character. though I am receiving an error msg saying: Error #1010: A term is undefined and has no properties.
at Mainas()
Could somebody please help me out on this matter.
Thank you.

package{
import flash.display.MovieClip;
import flash.events.MouseEvent;

public class Mainas extends MovieClip{
    var instructions:InstructionsPage;
    var gameScreen:GameScreen;
    var endGameScreen:EndGameScreen;
    var sc:Scuba
    
    public function Mainas(){
    instructions = new InstructionsPage();
    gameScreen = new GameScreen();
    endGameScreen = new EndGameScreen();
    sc = new Scuba
    
    instructions.playBtn.addEventListener(MouseEvent.CLICK,gotoGame);
    gameScreen.endgameBtn.addEventListener(MouseEvent.CLICK,endGame);
    endGameScreen.playagainBtn.addEventListener(MouseEvent.CLICK,playAgain);
    
    gameScreen.upBtn.addEventListener(MouseEvent.CLICK,moveUp)
    gameScreen.downBtn.addEventListener(MouseEvent.CLICK,moveDown);
    gameScreen.leftBtn.addEventListener(MouseEvent.CLICK,moveLeft);
    gameScreen.rightBtn.addEventListener(MouseEvent.CLICK,moveRight);
    gameScreen.rotateBtn.addEventListener(MouseEvent.CLICK,rotate);
    gameScreen.biggerBtn.addEventListener(MouseEvent.CLICK,makeBigger);
    gameScreen.smallerBtn.addEventListener(MouseEvent.CLICK,makeSmaller);
    gameScreen.visibleBtn.addEventListener(MouseEvent.CLICK,makeInvisible);
    
    init();

    addChild(instructions);
    }

    private function gotoGame(evt:MouseEvent):void{
        removeChild(instructions);
        addChild(gameScreen);
        sc.x = 320;
        sc.y = 300;
        addChild(sc);
        }
        
        private function endGame(evt:MouseEvent):void{
            removeChild(gameScreen);
            addChild(endGameScreen);
            }

        private function playAgain(evt:MouseEvent):void{
            removeChild(endGameScreen);
            addChild(instructions);
            }
                
    private function moveUp(event:MouseEvent):void{
        sc.y -= 10;
    }
    
    private function moveDown(event:MouseEvent):void{
        sc.y += 10;
    }
    
    private function moveLeft(event:MouseEvent):void{
        sc.x -= 10;
    }
    
    private function moveRight(event:MouseEvent):void{
        sc.x += 10;
    }
    
    private function rotate(event:MouseEvent):void{
        sc.rotation += 10;
    }
    
    private function makeBigger(event:MouseEvent):void{
        sc.scaleX = sc.scaleY += 0.1;
    }
    
    private function makeSmaller(event:MouseEvent):void{
        sc.scaleX = sc.scaleY -= 0.1;
    }
    
    private function makeInvisible(event:MouseEvent):void{
        sc.visible=false;
    }
    
                
                }
            }