One of the most wonderful games of the last decade.
I remember playing this when I was young - I had it on my XT for quite a while (and still do). I think that for a CGA/EGA game, the graphics are really good.. the game is very hard (I never managed to get past level 3, as far as I recall) and really interesting.
It has all sorts of little secrets and stuff you find if you shoot things, and is generally an interesting concept.
Well, it's difficult, but other than that... nothing comes to mind.
The Bottom Line
Recommended, very recommended.