MainWindow.xaml.cs

        private void border1_Click( object sender, RoutedEventArgs e )
        {

            Point p = ( ( MouseEventArgs )e.OriginalSource ).GetPosition( border1.Child );
            Vector2D v = new Vector2D( p.X, p.Y );
            v = v * multransform + addtransform;
            SkillTree.SkillNode node = null;

            var nodes = Tree.Skillnodes.Where(n => ((n.Value.Position - v).Length < 50));
            if (nodes != null && nodes.Count() != 0)
            {
                node = nodes.First().Value;

                if (Tree.SkilledNodes.Contains(node.id))
                {
                    Tree.ForceRefundNode(node.id);
                    UpdateAllAttributeList();

                    prePath = Tree.GetShortestPathTo(node.id);
                    Tree.DrawPath(prePath);
                }
                else if (prePath != null)
                {
                    foreach (ushort i in prePath)
                    {
                        Tree.SkilledNodes.Add(i);
                    }
                    UpdateAllAttributeList();
                    Tree.UpdateAvailNodes();

                    toRemove = Tree.ForceRefundNodePreview(node.id);
                    if (toRemove != null)
                        Tree.DrawRefundPreview(toRemove);
                }
            }
            tbSkillURL.Text = Tree.SaveToURL( );
        }