/// <summary>
/// sets the right sizes of the objects according to the screen size
/// </summary>
/// <param name="canvas"></param>
private void InitSizes(Canvas canvas)
{
resume.UpdateSize(canvas);
pause.UpdateSize(canvas);
start.UpdateSize(canvas);
ball.SetRadius(canvas);
TopBat.SetSize(canvas);
BottomBat.SetSize(canvas);
}