This is how stealth needs to be done!
A very nice game. In the beginning it actually gave that nice feeling of discovery that only a few games are able to deliver.
I don't have that much experience about stealth in games in general, but from the experience I've had, I think that at least sometimes the problem lies in failing to find the right balance between realism and good gameplay. True realism would require very complicated rules, but on the other hand good gameplay should often be based on relatively simple, easily understandable rules.
I think many games try to reach the realism without really succeeding in that, but by trying to do so, they also make the rules too obscure for ideally fun gameplay: the player doesn't that easily know what are the things that the enemies actually do easily notice and what are the things that the enemies do not notice. Or then it might be that I just haven't played good stealth games. :)
Any way this game shows, that stealth can work in a game. Simple rules, and even though the enemies are stupid, their behaviour can be understood, and there is a clear way their area of vision is visualized.
Now as for the game itself. The gameplay combines skill with tactics in a nice way, with the luring sounds and all. The graphics are extremely simple, but that doesn't really matter much. One thing that I would perhaps include though would be some kind of a level skipping possibility, since this is a quite tough game. Of course you shouldn't make it too easy with that either. Maybe you could get 1 skip per 30 or 40 stars or something. :) But this is of course a matter of taste. As I'm writing this, I'm at level 28.
All in all, this is a nice game that stands out for being different in a positive way. Score 8+/10. If you make a sequel that somehow offers an even better gaming experience, eg. with more interesting gameplay elements, more variation to the levels, more of a plot or character, or more features like a game editor, that could very well be worth a 10.