Alright, I played the game for a while.
I really like the concept and the atmosphere. I imagine that you get by by hearing things, which is why throwing pebbles helps you get around. I like that everything is pretty dark and the light is limited.
The levels so far have been okay too. I'm only at level 4 though, as I ran into a weird issue.
I don't like the fact that your character always turns to face the right direction when you jump from standing still. It gets annoying if you want to stand still, jump and throw something to the left.
The grenades were an okay mechanic, as was the gun.
I think it should be more clear that restarting the level will also reset all the levers and platforms, whereas dying will only move you to the start of one.
The enemies are okay as well. They are simple, but do their job.
The moving platforms work fine, but there's a weird thing when they run into eachother, which can happen in level 4, for instance. You will end up jerking a bit and going through one if they crash.
Now, about the level I got stuck on (level 4). I think I did pretty much everything. The objective, is of course, to get rid of the lasers blocking the door. However, I went to all the places, and turned all the levers. The one down at the bottom right, which recommends you shoot it (it is actually possible to jump over there). the three at the top (start of the level), and the one to the very left which also gets some platforms moving (like the one that moves across almost the entire map).
Still, when I get back there's still one laser in the way of the door out.
I might've missed something (I did find the grenades too), or then I ran into a glitch or something.
I can't comment too much on the story, as I have not been able to finish the game.
All in all, I don't think the game should be much longer. There are a few more things that could be done with the level tools, but after a while, I think it would get boring. Anyhow, this is a pretty good game, and I enjoyed playing it.
Good job!