Creating the animator and the gravity behaviour to animate our square

FallingSquareViewController.swift

    lazy var animator: UIDynamicAnimator = {
        return UIDynamicAnimator(referenceView: self.animationView)
        }()
    
    lazy var gravity:UIGravityBehavior = {
        let lazyGravity = UIGravityBehavior()
        return lazyGravity
        }()
        
    func animateSquare(){
        // 1. Add behaviors to the animator
        animator.addBehavior(gravity)

        // 2. Add items to the behavior
        gravity.addItem(squareView)
    }