A portion of a G4 interview with GameFreak director Junicihi Masuda and game designer Takeshi Kawachimaru...

G4: Many people erroneously think that Pokemon games are just for children, but there are many complex features in the game like IVs, EV training, Hidden Power, and more. How did these features come about?

JM: The reason why we put things like IVs and EVs into the game is because we wanted to give players that are really into Pokemon battles much more to work with and much more to enjoy. We have a team that's dedicated to constantly enhancing and evolving the battle system. They have so many ideas and such a willingness to enhance the game. They're always thinking of ways to make battles more interesting. One example from this generation is that they separated moves into physical attacks and special attacks, which adds more versatility and strategy to both offense and defense. They always listen to player feedback and they battle a lot themselves. This team is the reason why Pokemon has such a rich battle system that's always evolving.

Check out the full interview here (thanks Oscar and Joe!)