The reversed skill tree system is brilliant! I played it for a long while as I tried to get my high score.
Ultimately, I ended up with a score of 6 turns. The balance of this game is also brilliant! I found astronomy to be navigation, which directly depends on astronomy---so I would need an extra turn to clear off an era. I'm really curious how your team finished the game in 5 turns, since I tried a lot of combinations but ultimately it still took an extra turn to clear off navigation. I loved this gameplay and wanted to know the optimal solution haha:D
In addition, I loved the visuals, especially the hilarious "wise" words said by the monkey!
Great job overall!