Build more supervision buildings. For example, one base power plant needs 10 seconds, then two base power plants need 0.6× 10=6 seconds, and three base power plants need 0.8×0.6× 10=4.8 seconds, and each additional one needs 0.8 seconds. As for the fastest speed, it seems that I have never tried it. At most, I built sixteen chariot factories at a time, and the apocalypse was similar to that of infantry. ...