Vanilla

Fine tuning applied to selection areas, and think I've eliminated an odd bug that cropped up when you clicked and dragged and a new node appeared unexpectedly.

That's that, so next up is actually looking into whether I can also make this auto-detect if a graph is a tree, and if so then allow the standard A-level tree algorithms to be run (as well/instead), ie traversals.

As usual, Windows exe file attached for convenience.