Since I'm not done exploring what I want to explore in Normal mode, might as well start off with some Normal Mode boss fights. Their pattern isn't that hard to recognize really. Just aim at one direction and wait for them to switch sides if you're going for the Medals (I have the Gold and Bronze ones, Silver is up next), since you would need to kill them both at the same time. On the average, your play time with them should easily be under 1 minute.