He breaks the enemy units down to "grunt," "grunt leader," and "boss." Sato explains that the "grunts" are essentially pushovers and the challenge they present is not simply just to defeat them, but to defeat them in the most stylish way possible, for the most points possible. Sato says that in a game "where running around killing all the enemies is supposed to be fun, making them so hard that you can't kill them wouldn't be fun at all."
However, for those that crave difficult combat, the "grunt leader" is always on hand to provide an ample spanking. This guy is a bit tougher to battle, so it's not as much about getting the most points possible as it is about just surviving his attacks. Then, there are the "bosses," which are pretty self-explanatory.
Sato also tells us of a cool in-game item called the "Money Grubber," a briefcase stuffed with money that you throw at enemies. Once the "grunts" see it, they'll start clawing for it, and eventually fight each other over the money. While they're busy, Sato offers a few ideas, including tossing "a drum filled with gasoline their way" and even tossing the case "onto some busy train tracks."