Minimalistic expandable angular tree

http://angularjs.org/

HTML

<script type="text/ng-template"  id="tree_item_renderer.html">
    <span  ng-dblclick="expand_collapse(data)">{{data.name}}</span>
    <!--<button ng-click="add(data)">Add node</button>
    <button ng-click="delete(data)" ng-show="data.nodes.length > 0">Delete nodes</button>
    <button ng-click="expand_collapse(data)" ng-show="data.show && data.nodes.length > 0">collapse</button>
    <button ng-click="expand_collapse(data)" ng-show="!data.show && data.nodes.length > 0">expand</button> -->
    <ul ng-show="data.show">
        <li ng-repeat="data in data.nodes" ng-include="'tree_item_renderer.html'" class="{{!data.nodes.length ? 'empty' : (data.show ? 'down' : 'right')}}"></li>
    </ul>
</script>

<ul ng-app="Application" ng-controller="TreeController">
    <li ng-repeat="data in tree" ng-include="'tree_item_renderer.html'" class="{{!data.nodes.length ? 'empty' : (data.show ? 'down' : 'right')}}"></li>
</ul>

CSS

ul {
  list-style: none;
  cursor: pointer;
  -webkit-user-select: none;
  -moz-user-select: none;
  -khtml-user-select: none;
  -ms-user-select: none;
}
ul li:before {
	content: "";
  border-style: solid;
  display: block;
  height: 0;
  width: 0;
  left: -1em;
  top: 0.9em;
  position: relative;
}
/* top right bottom left */
ul li.down:before {
  border-color: #111 transparent transparent;
  border-width: 0.45em 0.35em 0 0.35em; 
}
ul li.right:before {
  border-color: transparent #111;
  border-width: 0.35em 0 0.35em 0.45em;
}
ul li.empty:before {
  border-color: #111;
  border-width: 0.2em 0.2em 0.2em 0.2em;
}
li {
    margin-left: 20px;
}

JavaScript

angular.module("myApp", []).
controller("TreeController", ['$scope', function($scope) {
    $scope.delete = function(data) {
        data.nodes = [];
    };
    $scope.expand_collapse = function(data) {
    		if(!data.nodes.length) return;
        data.show = !data.show;
    }          
    $scope.add = function(data) {
        var post = data.nodes.length + 1;
        var newName = data.name + '-' + post;
        data.nodes.push({name: newName, show: true, nodes: []});
    };
$scope.tree = [{name: "Node", show:true, nodes: []}];
}]);