Hi guys.. I was wondering how i could unlock all of thechallengearenas.. Ive completed the game on normal mode (im trying it on hard, but it is pretty hard) and done most of the riddles.. and i still have at least 5 arenas still locked! The levels that are unlocked i have completed with all therequiredchallenges..Does anyone know how i go about unlocking the rest of them.

I only have one stealth mission.. I really want more! thanks