code: function Quadtree(bounds, max_objects, max_levels, level) {
         this.max_objects = max_objects || 4;
         this.max_levels = max_levels || 4;
         this.level = level || 0;
         this.bounds = bounds;
         this.objects = [];
         this.nodes = [];
       }
docs: Quadtree Constructor <br>
  note: the global quadtree instance is available through `me.collision.quadTree`
  @class
  @name QuadTree
  @extends Object
  @memberOf me
  @constructor
  @see me.collision.quadTree
  @param {me.Rect} bounds bounds of the node
  @param {Number} [max_objects=4] max objects a node can hold before splitting into 4 subnodes
  @param {Number} [max_levels=4] total max levels inside root Quadtree
  @param {Number} [level] deepth level, required for subnodes