.directive( 'shift', [ '$animate', function( $animate ){
        return {
            restrict    : 'A',
            priority    : '400',
            terminal    : true,
            transclude  : 'element',
            link        : function( $scope, $element, $attrs, ctrl, $transclude ) {
                var
                    child = open();

                $scope.$watch( $attrs.shift, function( curr, prev ) {
                    if ( curr === prev ) {
                        return;
                    }
                    shift();
                });

                function shift(){
                    close( child );
                    child = open();
                }

                function open(){
                    var child = {};
                    child.scope = $scope.$new();
                    $transclude( child.scope, function( clone ){
                        child.element = clone;
                        child.element.addClass( 'ng-shift ng-shift-enter' );
                        $animate.enter( clone, $element.parent(), $element );
                    });
                    return child;
                }

                function close( child ){
                    if ( child.element ) {
                        child.element.removeClass( 'ng-shift-enter' );
                        child.element.addClass( 'ng-shift-leave' );
                        $animate.leave( child.element );
                        delete child.element;
                    }
                    if ( child.scope ) {
                        child.scope.$destroy();
                        delete child.scope;
                    }
                }
            }
        }
    }]);