Screens are Rounded Rectangles.

Implementing Rounded Corners in iOS

//  AppDelegate.swift

import UIKit

@UIApplicationMain
class AppDelegate: UIResponder, UIApplicationDelegate {
    
    var window: UIWindow?
    var activeCornerRadius : Int = 6
    var incativeCornerRadius : Int = 0
    
    func application(application: UIApplication!, didFinishLaunchingWithOptions launchOptions: NSDictionary!) -> Bool {
        window!.clipsToBounds = true
        
        var animation : CABasicAnimation = CABasicAnimation(keyPath: "cornerRadius")
        animation.timingFunction = CAMediaTimingFunction(name: kCAMediaTimingFunctionEaseOut)
        animation.fromValue = activeCornerRadius
        animation.toValue = 6
        animation.duration = 0.15
        window!.layer.cornerRadius = 6
        window!.layer.addAnimation(animation, forKey: "cornerRadius")
        
        return true
    }
    
    func applicationWillResignActive(application: UIApplication!) {
        var animation : CABasicAnimation = CABasicAnimation(keyPath: "cornerRadius")
        animation.timingFunction = CAMediaTimingFunction(name: kCAMediaTimingFunctionEaseOut)
        animation.fromValue = 6
        animation.toValue = 0
        animation.duration = 0.15
        window!.layer.cornerRadius = 0
        window!.layer.addAnimation(animation, forKey: "cornerRadius")
    }
    
    func applicationDidBecomeActive(application: UIApplication!) {
        var animation : CABasicAnimation = CABasicAnimation(keyPath: "cornerRadius")
        animation.timingFunction = CAMediaTimingFunction(name: kCAMediaTimingFunctionEaseOut)
        animation.fromValue = 0
        animation.toValue = 6
        animation.duration = 0.15
        window!.layer.cornerRadius = 6
        window!.layer.addAnimation(animation, forKey: "cornerRadius")
    }
}