One thing that is surprising about this game is just how similar the gameplay is from prehistory through enlightenment, with each age basically just increasing scale. So far it works historically, but it would be thoroughly disappointing if this continues into industrial as walls more or less became obsolete with the introduction of mechanized warfare. Changing this dynamic will require fundamental changes to the game engine (think trenches, urban warfare, explosive shells, multi-kilometer-range artillery, eventually flight, etc.).