         
         switch reason {
         case .newDeviceAvailable:
-            NSLog("Audio seesion route changed: new device available.")
+            print("Audio seesion route changed: new device available.")
             break
         case .oldDeviceUnavailable:
-            NSLog("Audio seesion route changed: old device unavailable.")
+            print("Audio seesion route changed: old device unavailable.")
             break
         default:
-            NSLog("Audio seesion route changed: \(reason.rawValue)")
+            print("Audio seesion route changed: \(reason.rawValue)")
             break
         }
     }

        slider.setProgress(volume, animated: true)
        
        do { try setSystem(volume: value) }
        catch { NSLog("unable to change system volume level.") }
       
        UIView.animateKeyframes(withDuration: animated ? 2 : 0, delay: 0, options: .beginFromCurrentState, animations: { () -> Void in
            UIView.addKeyframe(withRelativeStartTime: 0, relativeDuration: 0.1, animations: {

    
    @objc private func orientationDidChange(_ notification: Notification) {
        // TODO: [wip] support landscape mode.
        // print("orientation changed.")
        /**
        let currentOrientation = UIDevice.current.orientation
        switch currentOrientation {
