So the extension is pretty good, but there is one problem. The "Missing Resources" field (displayed as a negative number under the total amount of resources needed) and the "Buildable in" field get a little inaccurate after a moment. I think this is due to the fact that you actualize the first field's numbers in comparison to time, and I think it might be better for you to actualise it in comparison to the resources the player has. Otherwise great extension. :)