Interesting. My biggest mistake (besides excessing a ton of metal) was right near the beginning. I sent forward a group of glaives that arrived at Superninja's base shortly after a constructor left. Since he hadn't grabbed any mexes outside of his base, I assumed that no constructors had yet left his base. Therefore, early on I thought I was expanding faster and had more time. And while I got the turtle-shell award, tactically I think I lost more important assets to Superninja's towers than vice-versa.