public void undonode ()
	// Undo everything that has been changed in the node.
	// (This will not correct the last move marker!)
	{
		Node n = Pos.node();
		clearrange();
		ListElement p = n.lastchange();
		while (p != null)
		{
			Change c = (Change)p.content();
			P.color(c.I, c.J, c.C);
			P.number(c.I, c.J, c.N);
			update(c.I, c.J);
			p = p.previous();
		}
		n.clearchanges();
		Pw -= n.Pw;
		Pb -= n.Pb;
	}