SwiftPong（NoSpriteKit）：如何计算移动球的角度

我正在尝试使用Swift制作游戏Pong，但不使用SpriteKit。到目前为止，我已经能够在视图上成功绘制一个矩形，并且能够在屏幕上拖动它。这是我当前的代码：

import UIKit

class PongView: UIView {
    lazy var paddle: CGRect = {
        return CGRect(x: 200,
                             y: 200,
                             width: self.frame.width / 6,
                             height: self.frame.height / 60)
    }()
    var movePaddle = false

    required init?(coder aDecoder: NSCoder) {
        super.init(coder: aDecoder)
        let gesture = UIPanGestureRecognizer(target: self, action: #selector(dragPaddle(recognizer:)))
        addGestureRecognizer(gesture)
    }

    override func draw(_ rect: CGRect) {
        drawPaddle(rect)
    }

    func drawPaddle(_ rect: CGRect) {
        let path = UIBezierPath(rect: paddle)
        UIColor.black.set()
        path.fill()
    }

    func paddleInBounds() -> Bool {
        //padding vars are calculated in another file
        return (paddle.minX >= frame.minX + leftPadding) &&
               (paddle.maxX <= frame.maxX - rightPadding) &&
               (paddle.minY >= frame.minY + topPadding) &&
               (paddle.maxY <= frame.maxY - bottomPadding)
    }

    func setPaddleInBounds() {
        if (paddle.minX  frame.maxX - rightPadding) {
            paddle.origin.x = frame.maxX - rightPadding - paddle.width
        }
        if (paddle.minY  frame.maxY - bottomPadding) {
            paddle.origin.y = frame.maxY - bottomPadding - paddle.height
        }
    }

    @objc func dragPaddle(recognizer: UIPanGestureRecognizer) {
        print(paddle.origin)
        print(paddle.minX)
        print(paddle.minY)
        if paddleInBounds() {
            let translation = recognizer.translation(in: self)
            paddle.origin = CGPoint(x: paddle.minX + translation.x, y: paddle.minY + translation.y)
            recognizer.setTranslation(CGPoint.zero, in: self)
            setNeedsDisplay()
        } else {
            setPaddleInBounds()
        }
    }
}

现在，我想创建一个球。不过，我不确定如何开始。碰撞应该很容易：

if (ball coordinates are within boundaries) || 
   (ball coordinates touch paddle coordinates) {
    //collision detected
}

但是，如果没有SpriteKit，我不确定如何计算球的弹跳角度并相应地移动球，这是游戏的主要部分。有什么建议么？