Great job, really cool mechanic!  I think having a bit more audio for the ghouls, like ping when the ghoul is hit, and when it starts moving (if those sfx did exist, I couldn't hear them).  Also adding contrast adjustment would be nice, as well as gamepad support.

I'll admit, I'm a sucker for sonar-based gameplay (once made a fully-dark-but-with-sonar asteroids), and this is a pretty good implementation of it. It's a shame death means resetting the whole game, because I didn't quite feel like redoing the first four levels after dying (and the noise covering the screen was getting a bit unpleasant). But until that point I had a lot of fun attacking the darkness!

Really unique and well-polished gameplay, I really enjoyed it, especially once I found out that if I don't charge the sonar, it will still travel the distance, only at a narrower angle. It feels really rewarding to shoot one of those thing at the last minute.

Some improvement ideas:

• There should be a way to turn off or tone down the screen effect, it was really hurting my eyes after a while.
• It would be probably friendlier to reset the player to the beginning of the same level instead of level 1, or maybe give three attempts before the final reset, it feels bad to lose all progress.
• Some kind of a narrative, even an intro and some small snippets before each level would really add to the feel, while I was roaming those halls and looking for these weird monstrosities, I felt like I want to know where I am, what they are and where they came from.

Overall, nice work with the smooth gameplay and the sounds effects.

Good game. I got scared a little but I like it.

The game mechanics were really unique and interesting, I liked the gameplay although it took  a while to charge the scan. Im not sure how to balance that though so it makes sense. Really cool concept!

Good job, I discover it was way easier after being able to spam the light down the hall way and using the big bursts to decided what hallway I wanted to go to. great mechanic. 

This one gave me the willies well done, this can be greatly expanded upon into a full game.

Great game!  I got jump scared a few times.  I wish there was more ambiance and music and a visual indicator that one died and not just the window popping up.  The player character controlled a little too sluggish for my taste.  I also wish there were more landmarks in order to memorize the locations / enemies placements a bit better.  Couple menu glitches.  Game like these with the light pulse mechanic are unique and interesting.  Overall, terrific job!

Edit:  I played up to middle of level 2.