         let button = UIBarButtonItem(title: NSLocalizedString("Next", comment: ""), style: .Plain, target: self, action: "next:")
         return button
         }()
+
+    var isDirty = false {
+        willSet {
+            nextButton.enabled = newValue
+            promptTermsLabel.alpha = newValue ? 1.0 : 0.5
+        }
+    }
 
     override func viewDidLoad() {
         super.viewDidLoad()


        promptTermsLabel.attributedText = attributedText
        promptTermsLabel.textAlignment = .Center

        promptTermsLabel.userInteractionEnabled = true
        let tap = UITapGestureRecognizer(target: self, action: "tapTerms")

    }

    func textFieldDidChange(textField: UITextField) {
        isDirty = !textField.text.isEmpty
    }

    func next(sender: UIBarButtonItem) {
