angularjs validation css tutorial

<!DOCTYPE html>
  <html>
    <head>
      <title>Wikitechy AngularJS Tutorials</title>
      <script src="https://ajax.googleapis.com/ajax/libs/angularjs/1.5.6/angular.min.js"></script>
      <style>
        input.ng-pristine {
            background-color:orange;
        }
        input.ng-touched.ng-invalid {
            background-color:red;
        }
        input.ng-touched.ng-valid {
            background-color:green;
        }
      </style>
    </head> 
    <body>
      <h3>AngularJS HTML CSS Class Validation </h3>
      <form ng-app="myApp" ng-controller="inputCtrl" name="myform">
        Enter Mobile Number : 
        <input type="text" name="number" ng-model="number" required ng-minlength="10" ng-maxlength="13" ng-pattern="/^[0-9]+$/">
        <input type="submit" ng-click="submit()" value="Submit" />
      </form>
      <script>
        var app = angular.module("myApp", []);
        app.controller("inputCtrl", function($scope) {
          $scope.submit = function() {
            if($scope.myform.$valid) {
              alert("Form Submitted Successfully!" );
            }
            else {
              alert("Invalid Form!" );
            }
          };
        });
      </script>
     </body>
  </html>