I recall the aspects of a game from a number of years ago -- pre trading, pre a lot of things. I was under pressure from one side (about Prince level, but it still a challenge for me at the time) & I was defending my continent , & otherwise was perfecting the landscape, RR & Farms everywhere. Science every four turns or so -- had maybe a third of the Wonders. No trade routes, no a rifle or two defending every city (all 15 of them) when I get the enemy pouring in from another sector the 20 cities of the Indians open up a new front.
Replayed the entire game with a new awareness -- I need more cities in the NW, before they came over & closed the isthmus. Second time through, I had about 30 cities & built a fine spaceship.
Lesson learned -- grow; build more cities -- something the five advisors never offer. actually lesson only semi-learned -- I still dont get out the door fast enough & dont shift over to the offensive soon enough.