Wow! I love your take on the theme and I think you nailed the sound design and atmosphere. Making a game in complete darkness sounds next to impossible to me, and you managed to pull it off so well! However...
I think that the echolocation-cooldown could be a little shorter. Either that or increasing the area affected because right now I found myself taking a step, then checking for dangers, taking a step, then checking for dangers, and so on.
Other then that, the gameplay is unique and really enjoyable.
I really hope that you continue to develop this game.
Cheers!