 	func thumbImage(state: ControlState) -> Image
 }
 
-protocol Stepper {
+//class
+protocol Stepper: VisibleMediaObject {
 	var continuous: Bool { get set }
 	var autorepeats: Bool { get set }
 	var wraps: Bool { get set }

    
}

protocol Timer {
    var valid: Bool { get }
    var fireDate: NSDate { get set }
    var interval: Double { get }

    func initialize(url: NSURL, frame: C4Rect)
}

//class
protocol Sound: MediaObject {
    var pan: Double { get set }
    var player: AVAudioPlayer { get }
    var numberOfChannels: Int { get }
