如何防止处理触摸位置的SKShapeNode超出圆路径？

import SpriteKit

class GameScene: SKScene {
    var circleNode: SKShapeNode!
    let circleRadius: CGFloat = 100.0
    
    override func didMove(to view: SKView) {
        // 创建圆形路径
        let circlePath = UIBezierPath(arcCenter: CGPoint.zero, radius: circleRadius, startAngle: 0, endAngle: CGFloat.pi * 2, clockwise: true)
        
        // 创建形状节点
        circleNode = SKShapeNode(path: circlePath.cgPath)
        circleNode.fillColor = .blue
        circleNode.position = CGPoint(x: frame.midX, y: frame.midY)
        
        // 添加形状节点到场景
        addChild(circleNode)
    }
    
    override func touchesMoved(_ touches: Set<UITouch>, with event: UIEvent?) {
        guard let touch = touches.first else { return }
        
        // 获取触摸位置
        let touchLocation = touch.location(in: self)
        
        // 计算触摸位置与圆心的距离
        let distance = sqrt(pow(touchLocation.x - circleNode.position.x, 2) + pow(touchLocation.y - circleNode.position.y, 2))
        
        if distance > circleRadius {
            // 计算触摸位置在圆上的坐标
            let angle = atan2(touchLocation.y - circleNode.position.y, touchLocation.x - circleNode.position.x)
            let x = circleNode.position.x + cos(angle) * circleRadius
            let y = circleNode.position.y + sin(angle) * circleRadius
            
            // 更新形状节点位置
            circleNode.position = CGPoint(x: x, y: y)
        } else {
            // 更新形状节点位置为触摸位置
            circleNode.position = touchLocation
        }
    }
}