One other tip for getting the hard badge, when reaching the 3rd/4th month of the game, DO NOT graduate a student until you have an extra student to back up with that is equally or stronger than the student you want to graduate.
You know, I would rate this pretty high if the freaking AI won't stop getting stuck on some stupid spots and run in place, not helping me out killing enemies.
"Take out the gunner underneath the north building next to the sandbags."
Well why does the rest get alarmed? Apparently, you're supposed to shoot at the guy on the northwest building.
To everyone who wants a 4th sequel:
SHINKI is NOT GOING TO MAKE SCGMD4!!! It's answered in the Shinki Productions FAQ, HE DOES NOT WANT TO MAKE A 4th sequel.
Quick Level Tip: When doing Level 10 on all three challenges, blow up the oil truck to release a car that destroys a bank and moves into the train tracks which a train stops and the next train crashes onto it.
One thing though, how do all those writings fit into the paper plane? There's the girl's note a love letter filling one page, the end of the world, a boy who thought the plane was a dead bird (not included), and some japanese hobo wishing to be famous writing his composition lyrics.
 "Hacker vs Hacker"){kind=icon}
 "Papa's Taco Mia!"){kind=icon}
 "Valthirian Arc"){kind=icon}
 "Upgrade Complete 2"){kind=icon}
 "Tactical Assassin 3"){kind=icon}
 "Super Crazy Guitar Maniac Deluxe 3"){kind=icon}
 "Bullet Heaven"){kind=icon}
 "Roadkill Revenge"){kind=icon}
 "The Legend of the Golden Robot"){kind=icon}
 "Flight"){kind=icon}
 "Reactance"){kind=icon}