code: @Override
  	public KdTree.Node findNeighbor(P target) {
  		if( tree.root == null )
  			return null;
  
  		this.target = target;
  		this.closest = null;
  		this.bestDistanceSq = maxDistanceSq;
  
  		stepClosest(tree.root);
  
  		return closest;
  	}
docs: Finds the node which is closest to 'target'
  
  @param target A point
  @return Closest node or null if none is within the minimum distance.