It is the Year of Our Lord 1510, and one has to wonder how differently history could have played out if Niccolò Machiavelli, the military commissioner of the Republic of Florence, had not understood the true scale of Leonardo da Vinci’s genius. In such a world, the visionary might simply have wasted his time painting portraits of women and doodling in a sketchbook. Instead, he unleashed a technological revolution where primitive computers, decorated with delicately painted cupids, run on water clocks; spring-powered tanks whir across the battlefield, with cannons thundering from their flanks; and gliders flit across perfectly blue Tuscan skies.