BELIEVE IN THE ME THAT DOESN'T BELIEVE IN YOU
then give up because your friend's been playing way more Civ than you and already has mechanized infantry in 1500 AD
Something tells me Chrome is going to come up with something original right at the end of the story and he'll be like "look I know this has probably been invented but..."
But man, Chrome is the smartest guy in this manga. He invents tools that is present in the modern world sure it is funny cause modern man knows what it is but Chrome is from stone age .