You've spent hours memorizing Yellow Devil's movement patterns. You seem to be able to instinctively, almost clairvoyantly, know when you’ll find the next energy pellet so you can push your damage meter to the very edge before you have to refill. You can jump over every one of Gutsman's attacks. You can even beat Metalman without taking a single point of damage using only the Buster Shot, because charging shots just slows you down. You know everything there is to know about the Mega Man...
