override func viewDidLoad() {
super.viewDidLoad()
//グラデーションの開始色
let topColor = UIColor(red:147, green:6, blue:229, alpha:1)
//グラデーションの開始色
let bottomColor = UIColor(red:23, green:232, blue:252, alpha:1)
let gradientLayer = CAGradientLayer()
gradientLayer.frame = view.frame
gradientLayer.colors = [topColor.cgColor, bottomColor.cgColor]
gradientLayer.locations = [0.0, 1.0]
gradientLayer.startPoint = CGPoint(x: 0.0, y: 1.0)
gradientLayer.endPoint = CGPoint(x: 1.0, y: 1.0)
gradientLayer.cornerRadius = 20.0
self.view.layer.insertSublayer(gradientLayer, at: 0)
}

