I ask that because using the main cannon is damned impossible unless the enemy fighters get really close to it but not on top of it. By that time, they've already hit your ship for so much damage. Can I get to chapter 4 on hard mode without upgrading the main gun?
And yes, the strategy guide does seem to assume that you have at least 500RU at the start. It doesn't tell you what to do with the first 100RU. I think I'll be trying to complete the game without the strategy guide's aid.
father_alexander, your theory of just shooting around the zone and hoping for hits would be fine if the cannon fired one projectile every 0.1 seconds. Instead, it can't be any more than two per second, and the speed at which they travel is pretty much the same as the small enemies' speed. You have to predict where the enemy is going to fly to.
My only two platinums are in combos (133) and accuracy (142%) so I won't be going for the impossible badge. Not that it matters, because even when I'm not going for badges, this is still a fun game to play and the more intense music that comes in later is some of the most epic music I have ever heard.
Antarctic Chainsaw Massacre
Dude! You just completed the Antarctic Chainsaw Massacre achievement in Penguinz and won the Antarctic Chainsaw Massacre badge and 30 points! I fought the lag and I won!
 "faze"){kind=icon}
 "Death Vegas"){kind=icon}
 "Orbital Decay"){kind=icon}
 "Oozing Forever"){kind=icon}
 "RetroShoot"){kind=icon}
 "The Great Siege"){kind=icon}
 "me and the key"){kind=icon}
 "MAD: Mutually Assured Destruction"){kind=icon}
 "Farragomate"){kind=icon}
 "Exploit"){kind=icon}
 "Penguinz"){kind=icon}
 "The Great Sperm Race"){kind=icon}