Unnecessary tips: I found the "Special Weapons" to be the backbone of the middle game. I went Splitter->Plasma. Someone else suggested that you get regeneration early so you can get 3 stars on everything (by waiting to heal if you are less than 70%, before killing the last guy).
The fuhong puzzle has bugs. Semi-spoiler (really, it's a bug workaround). The email only worked for me in IE (!!?), not Firefox. The format is "reset password*newline*fuhong*newline*code". Clear error messages before trying.
QUESTION WITH SPOILERS. OK, what's up with Fuhong's computer? When I type resetpass, it tells me my password is 1b62ff22. I go to the website "http://mailer.mucomplex.com/", and send an email to "email@example.com" with the content "I would like a reset of fuhong; my ID is 1b62ff22". That email is rejected (along with several variations). Is my syntax wrong? Am I grabbing the password from the wrong location? (I tried the other passwords in the .mail files). Please give a tip! Thanks.
Challenge 16 took me more time than the rest of the challenges combined. I had a long unlucky streak, although I got lucky on 15 and a few others. It took a little bit, but I've had hard badges take longer than the impossible one here.
The level 7 challenge mode took me more tries than the final level hard mode in difficulty. An easy fix might be to increase the ball's hit zone a little (rolling *over* guys is more fun than trying to pinpoint them, anyway). I beat the final level with 2 cross/4sniper/red/black, and a little luck. Fun game!