Rating: Good, but too hard.
Positives:
(+) Working game.
(+) Good concept.
Negatives:
(-) No instructions.
(-) Steep learning curve.
(-) Just plain hard.
Overall:
Good game, I just don't like it because it's so hard... but I won't let that effect my review too much. You could've included a tutorial, easier levels, or, at the very least, instructions.
4 out of 5.