Put it simply it is a unique game. It has many flaws like every good "punk game" but it has an interesting spirit. This game clearly is aimed to VG lovers ( in certain point it has an Atari/Famicom taste ).
What I found amusing is that if you analyze the structure of this game you'll note that under the skin of "simple action" there is a structure that resemble a Shmups
( emblematic is the 5th killer were basically it is a vertical shmups in all sense and ,well, the 4th mission when you encounter that "Pure Glasborry" robot).
The game play with the gamer because he demand you to reflect on why you play.
NMH is cleary a meta-game, similar in some way to Grashopper's Contact on DS.
EDIT:
NMH is also a metaphor of Travis sex initiation.
“In the entertainment business, there are only heaven and hell, and nothing in between and as soon as our customers bore of our products, we will crash.” Hiroshi Yamauchi
TAG: Like a Yamauchi pimp slap delivered by Il Maelstrom; serving it up with style.
