oh 1 more thing regarding graphics and the delete box, if the box had a 1 pixel, solid trim around it, possibly with very slightly rounded corners I think that would look very nice as well.
And the X could be smaller, or potentially be removed (maybe an option?) since you're finger covers it up anyway the parts that stick out just block me from seeing the nodes I'm going over if I'm trying to be very precise. Maybe drop it lower in the Z buffer so it's behind the nodes? but that would probably look weird.
Again, gratz, awsome game!