 
     var applicationDelegate: AppDelegate
     {
-		return NSApplication.sharedApplication().delegate as! AppDelegate
+        return NSApplication.shared.delegate as! AppDelegate
     }
 
     var windowIsVisible: Bool = true


    private var letters: [Letter] = []

    func displayLetter(letter: Letter)
    {
        let letterCount = letters.count


        outputLetters.stringValue = ""
        for letter in savedLetters
        {
            display(letter: letter)
        }
    }

	@IBAction func clearOutput(sender: Any)
	{
        letters = []
        redisplayLetters()
