Ok, so, I voted low, and now I should say why. The art & mechanics are interesting, and the music is nice enough. It also has some challenges (getting through entire levels without dying, getting through the game without dying).
But there are problems. Deaths are penalized with the death animation, and a secondary game-over screen. A simple respawn here after a quicker animation is all that's necessary.
Secondly, there are a few bugs in hit detection: When climbing up to a ledge, if an enemy passes under you at the wrong time, even though your character will appear to be on the ledge, it appears that the hit detection teleports back to start then to the top. This can make a few moments in the game frustrating.
Finally, the ending is nothing special. There is no climax to the game, just a cessation of the game for now. Rather simply, this kills the game, because it's not really over, but there's no hint of what happens next. Just a cessation, so it's rather bland, and while you don't know what happens next, you don't care or fear either. Needs polish in that respect.
That said, decent art and atmosphere, but with a SMALL extra bit of HL-style storytelling, and a bug fixed here and there, it'd be 4 stars.