I thought I'd give it a go, but if I run make darkecho, I get an error: main.c:9:10: fatal error: SDL.h: No such file or directory. I dont think everyone has the sdl development headers installed. I installed them with sudo apt-get install libsdl2-dev.
Then I got an error that it could not find libm. I had to add -lm to the LDLIBS line in Makefile. Then it compiled.
And now it works! I played room.txt
You completed the level in 2 minutes and 39 seconds!
I think it's an open door to state that only someone experienced in the terminal can play the game. I'm sure you are aware. What I really liked is your echolocation system. It took me a minute to understand what I was listening at. But then I understood it's like a radar system going around and there are wall and bell sounds. After that, it was quite doable to collect the rings/bells! I go tthat ooooh feeling and wanted to finish the level, that counts for fun!
Well done on submitting something, even if it's a very rough gem. Hope you will create a linux/windows/mac executable for it, or at least a shell script to build the game, select the level and play ;).