Zombie Nation [Nes][CompleteTheGame]

It is the near future 1999.
A meteorite crashes in the Nevada Desert, carrying the evil alien Darc Seed.
He uses his strange magnetic rays to turn 98% of USA into highly advanced zombies (if zombies can use helicopters and airplanes, they must be highly advanced) which helps him taking over the country.
He also turned the Statue of Liberty into a giant Medusa for some reason.
Thanks to controlling the US military, he got access to many deadly weapons. But the deadliest weapon is an old legendary samurai sword named Shura.
And the moment Darc Seed touches Shura, the great samurai Kamakubi awakes from his slumber.
...or his head... he probably got his head cut off while dying, probably some honor-related thing.
His only goal is to prevent Shura from falling into the hands of evil, so he goes on a rampage killing tons of mindless American zombies. And if he find an un-affected person, he eats that person to become more powerful.
...you ask how a head can take back a sword?
Well, first of all it is a giant head.
...that floats...
...and he attacks by puking and shooting eyeballs...
...and the sword is never mentioned again...
Darc Seed himself is like a giant grey alien that can't move his body. He attacks by moving around some blue balls that kills everything they touch.

The game is kinda fun, but hard. The head got a momentum so it keeps moving for a while after you release the D-Pad. And there are a ot of bullets in the way in some places.
The good news is that you can take multiple hits. And when you kill enemies, you will start regenerate your health back.
The bad news is that you wont see your health at the boss fights, so you never know how near death you are.
The stage select at the start only allows you to chose which level to start on, you must still complete all four levels no matter where you begin.
And as usual, this gem was never released in Europe.