I played this game for years on my Atari ST. It is winable. Don't just rely on the swords and throwing stars - you can punch, kick, and even knock an enemy out by doing a front flip and landing on top of them. I can't remember all of the joystick moves or key stroke combos, though.
The top level is a single room where you face 5 ninjas in a kind of slow-motion mode.
There was a really cool glitch if you won (at least in the ST version). You could go back through and fight the ninjas on the other levels, but they wouldn't fight back. It was really funny. I'd play and my God-brother would make "dubbed voiceover" type comments.
I remember having both the music and the sound FX. What was cool was, if you won a room and got the music and you waited long enough, the music would change. It was pretty cool.
