Swift: Strange Collision Behavior - swift

Question

I'm building a Breakout game (#cs193p) and I've got the beginnings of the general working set up: The bricks, ball, and paddle all draw as they should. The collisions sort of work as they should, except the collision boundaries appear to be sort of wrong. They're generally larger than the paths I've constructed them with, but not always.
I've set the elasticity of the ball to zero, so that it rests on the paddle, so that the discrepancy is clear. This screenshot shows the ball resting on the incorrect collision boundary of the paddle.
The bricks and the black area at the bottom respond a little differently. For the bricks, the ball seems to be colliding with the bottom row of bricks when it visually reaches the next row. I've got the bricks disappearing "correctly" so the collision is doubly confirmed by the bricks disappearing. The black area at the bottom (the space for panning to move the paddle) has a similar issue: the ball dips a little into this area before bouncing.
Here is, well, a bunch of code, because I don't know where the problem might lie.
From my BreakoutBehavior class (I'm leaving out the gravity section because it doesn't seem to be a part of the problem):
let collider: UICollisionBehavior = {
let collider = UICollisionBehavior()
collider.translatesReferenceBoundsIntoBoundary = true
return collider
}()
private let ballBehavior: UIDynamicItemBehavior = {
let behavior = UIDynamicItemBehavior()
behavior.allowsRotation = true
behavior.elasticity = 1.25
return behavior
}()
internal func addColliderBoundary(path: UIBezierPath, named name: String) {
collider.removeBoundary(withIdentifier: name as NSCopying)
collider.addBoundary(withIdentifier: name as NSCopying, for: path)
}
override init() {
super.init()
addChildBehavior(gravity)
addChildBehavior(collider)
addChildBehavior(ballBehavior)
}
internal func addItem (_ item: UIDynamicItem) {
gravity.addItem(item)
collider.addItem(item)
ballBehavior.addItem(item)
}
And here's some code from my BreakoutView class:
I'm giving you the paddle as just one example of a boundary problem, rather than also giving the bricks and pan area, to be more efficient. So of course some of the variables I refer to won't be present in my excerpts. Note that I've left out some things like adding the behavior to the animator, but know that everything is indeed working, I'm just having these boundary problems.
private var paddleSize: CGSize {
return CGSize(width: brickSize.width * 3, height: brickSize.height)
}
private var paddleOrigin: CGPoint {
let x = frame.midX - paddleSize.width / 2
let y = panOrigin.y - paddleSize.height
return CGPoint(x: x, y: y)
}
private func addBallAndPaddle () {
let paddleFrame = CGRect(origin: paddleOrigin, size: paddleSize)
let paddleView = UIView(frame: paddleFrame)
paddleView.backgroundColor = UIColor.white
paddleView.layer.borderWidth = 0.25
addSubview(paddleView)
paddle = paddleView
behavior.addColliderBoundary(path: UIBezierPath(rect: paddleFrame), named: Boundaries.paddle)
let ballFrame = CGRect(origin: ballOrigin, size: ballSize)
let ballView = UIView(frame: ballFrame)
ballView.backgroundColor = UIColor.white
ballView.layer.borderWidth = 0.25
addSubview(ballView)
behavior.addItem(ballView)
ball = ballView
}
private lazy var animator: UIDynamicAnimator = {
let animator = UIDynamicAnimator(referenceView: self.superview!)
animator.delegate = self
return animator
}()
private lazy var behavior: BreakoutBehavior = {
let behavior = BreakoutBehavior()
behavior.collider.collisionDelegate = self
return behavior
}()
And here's code from the BreakoutViewController. configureGameView() is called in viewDidLayoutSubviews
private func configureGameView () {
gameView.frame = topView.frame // topView is the view in IB
gameView.backgroundColor = UIColor.lightGray
gameView.addViews() // adds bricks, ball, paddle, pan area
firstTap.numberOfTapsRequired = 1
gameView.addGestureRecognizer(firstTap) // DOESN'T WORK
if let panView = gameView.panner {
panView.addGestureRecognizer(UIPanGestureRecognizer(target: gameView, action: #selector(gameView.movePaddle(_:))))
panView.addGestureRecognizer(firstTap) // DOESN'T WORK
}
}
Thanks!