The first secret area is in the second mission. When you see five posts, (four green, and one red)destroy the four green ones first and then destroy the one red one. If you do this you'll finish the mission a different way without having to face the boss, and then you'll get to play a secret mission.
GamesRadar is the premiere source for everything that matters in the world of video games. Casual or core, console or handheld - whatever systems you own or whatever genres you love, GamesRadar is there to filter out what's worth your time and to help you get even more from your games. We deliver the best advice, the most in-depth features, expert reviews, and the essential guides for all the top games.