Ahh... I really like the idea of only seeing what echoes off walls. Really good idea! The simple controls also make it easy to understand & play. The 9-10 seconds of silence after you run out of echoes is super tense which I love. I got stuck at a point where I spawned with 0 echoes, but I had fun with what I played.
One suggestion, unrelated to the game tho, is to go for a Web build over a Windows build. Take a lot more effort to play the game when you have to download & extract vs. just clicking "Play".
Great job anyways!