I kind of expected to be lifted out of the plane at the end of the game, so that it would have at least one thing in common with the novel (well, apart from isosceles being lowlifes). ;)
One thing that is really annoying me: Unlocking higher difficulties in Survival Mode doesn't work properly half the time. I hate to get to 1500m in Normal Mode twice to unlock Hard Mode, and now I've finally gotten to 1000m in Hard Mode and it didn't give me Nightmare Mode. That bites. :(
Mr. Right achievement doesn't work. Also, it seems to be a bit laggy at times (not registering the key I pressed, resulting in a mistake for pressing the next key). Still, it's a decent and fun game.
@ Dataslayer: You NEVER have to guess on any kind of Sudoku, and your example was even pretty obvious (just look at the 4's). However, even on those extremely hard ones (which are not included in this game), there's always some advanced techniques (naked pairs/triples, mostly) which can be used to prevent having to guess.
If he does his attack where he shoots tons of small bullets, orient yourself to the right edge of the screen (NOT the corner). You should position yourself in the middle of the space between the bottom edge of the screen and the boss (vertically), not directly at the right edge, but pretty close. You might take some damage, but that's okay. You should now be in a larger diamond-shaped safe spot which moves slowly to the left and to the right again, just move with it. If you chose a safe spot too close to the bottom or the edge of the screen, you might get into problems when the bullet-lines move back to the right. Just fly through one stream of bullets into the safe spot directly left and above yours to avoid getting splattered. Hint: You might not have the time to move to your save spot before the bullets come in - just hurry and fly through them, you will still take less damage than by choosing a crappy safe spot on the left or something like that.
Acydyk already described how to dodge the missiles, but here's how to deal with the other ones (though not always without taking damage): The pulsar should be quite easy, just pay attention to the flashing lights at the boss's spikes and fly where there were none. If you get hit, this attack does quite a lot of damage. When he's shooting those small bullet-lines, move to the left-hand corner of the screen. The first two lines of larger bullets won't hit you. After the second line, move a little to the right to dodge the third one, then to the left again and back to the right for the fourth and fifth. After that, move through the lines of small bullets (you can do this very slowly and carefully).
Why do so many people think that the impossible badge is sooo hard (or "only acquired by hackers")? It takes waaay less practice and patience than the badges over at SCGMD, and the percentage needed on Eight Circles could really have been increased to 95%, since after practising the stairs a bit, it's not even harder than Seven Circles. A real impossible badge would be to get a crazy star on Dash Hopes 3, but that would just be mean. :) However, in my opinion, it would have been better to either require the player to get a star on ever song (except for Dash Hopes 3) or to finish every song without a single miss (percentage doesn't matter, but this time including Dash Hopes 3) to get the impossible. But it's too late for that anyways, and I'm happy with my impossible. :) And got a star on anything besides Dash Hopes 3.
Please, please, PLEASE lower the combat skill achievement requirement to 850, or at least 900. I have got every other achievement (well, doing the demon quest one in the next hours), and already farmed for a while, but I only have about 880 magic attack skill. 1000 really is too much. (Maybe you might also consider adding potions or books that add +5 to weapon/archery/magic skill, then 1000 might be reasonable.)
3. Difficulty: After correcting those pesky off-beat notes, you have a hard mode that is not really hard. My advice: Keep those three modes, but add a fourth mode that also uses all 5 notes (like in the real Guitar Hero), to satisfy the more professional player, too. :)
4. Configuration: A game like this just needs the option to manually choose the keys you want to use. Pretty self-explanatory.
As a foot note: I only played the basic ("tap") mode, because i do not like strumming on the PC keyboard. So everything I said is based on this mode.
All in all, it is at least a decent try, which is worth 3/5 points in my opinion. :)
I normally like these Guitar Hero style games - those of high quality, that is - but i did not really like this one.
Let me explain why:
1. Off-Beat: This, for this type of game, is an absolute no-go. I do not have a problem with single misplaced notes, but especially on the later songs with notes following quiet close to each other, it seems impossible to play the song and play the note chart at the same time. You must not just put some notes after each other if the music gets a bit faster.
2. Higher and lower notes: In my opinion, the notes on the right should be the higher ones and those on the left should be lower. Partly, this is not really considered, so that the notes just do not really fit the melody, but only the rhythm.
Ah, after thinking about it again, it seems logical to me, because the 0 is kinda easy to find, so it is clear that the person who made the note with the order of the colors found that one, too. In addition, the dice is more likely bound to the room because you do not need an extra item to find out its number so there is no need to take it with you.
 "Flatland: Fallen Angle"){kind=icon}
 "Boss Slayer"){kind=icon}
 "Running Fred"){kind=icon}
 "LethalRPGDestiny 2: Conquest"){kind=icon}
 "volcaNOM"){kind=icon}
 "Mix Sudoku Light Vol.1"){kind=icon}
 "Reactance"){kind=icon}
 "DJManiax"){kind=icon}
 "Arkandian Crusade"){kind=icon}
 "Santa Rockstar: Metal Xmas 3"){kind=icon}
 "Endless Migration"){kind=icon}
 "Cursor Catalog 2"){kind=icon}
 "Get Off My Lawn"){kind=icon}
 "GeoSketch"){kind=icon}
 "Detained"){kind=icon}