private void generateTree(Tree t, int layer, Chip first) {
                List connections = connectedChips(( Chip ) (t.getDatum()));
                ListNode ptr;
                Chip c;

                /**** DEBUGGING ****/
                int i = layer;
                while (i-- > 0)
                        System.out.print("-");
                ((Chip)t.getDatum()).printChip();

                try {
                        /* go through each possible connection */
                        for (ptr = connections.front(); ptr.isValidNode(); ptr = ptr.next()) {
                                c = (Chip)ptr.item();
                                /* add the chip to tree if it isn't in it already */
                                if (inTree(t, c) || straightLine(t, c) || inWrongZone(first, c))
                                        continue;
                                t.addChild(c);
                        }
                        if (t.getChildren().isEmpty())
                                return;
                        /* for each new child, call this recursively */
                        for (ptr = t.getChildren().front(); ptr.isValidNode(); ptr = ptr.next()) {
                                generateTree((Tree)ptr.item(), layer + 1, first);
                        }
                }
                catch (InvalidNodeException e) {
                }
        }