BallView.swift

class BallView: UIImageView {
    init(size: CGFloat) {
        super.init(frame: CGRect(origin: .zero, size: CGSize(width: size, height: size)))
        image = UIImage(named: "basketball-png-0")
        contentMode = .scaleToFill
        layer.cornerRadius = size * 0.5
    }
    
    required init?(coder aDecoder: NSCoder) {
        fatalError("init(coder:) has not been implemented")
    }

    override var collisionBoundsType: UIDynamicItemCollisionBoundsType {
        return .ellipse
    }
}