Hi there, first of all, great mod!
Recently the Mining Productivity technology underwent some drastic changes. The second Deep Mine research requires Mining Productivity 4, which in turn costs 2500 space science, putting the Deep Mine research a little bit too far down the research tree. So I humbly suggest to change the prerequisite to Mining Productivity 2, or Mining Productivity 3 and add Utility science to the Deep Mining 2 research cost. Also, it would be cool if Deep Mining 2 would have Deep Mining as prerequisite, so their connection is visible in the research tree.
Thank you very much.
