This is basically “winamp, but it plays (exclusively) .ogg files instead and is heavily optimized to provide the lowest CPU usage possible” – there’s an equalizer, playlist, a volume bar. A feature that minimizes CPU use when the application is on the foreground. And yes, the graph does work and is perfectly syncronized with the song. And all you see here are purely made of code – no .png or .bmp files included, don’t worry about it. And logically, no need to run wine or some other shoddy translation layer – it all runs natively on your PC.
CPU usage is comically low, as you can see here (tested on a orange pi 5 max):

To unpack the file, download dependencies and compile (on a debian distro, while in the same directory as where the llamamp.tar.gz file has been downloaded): tar -xf llamamp.tar.gz && sudo apt install -yq build-essential pkg-config libsdl2-dev && make -j$(nproc). Install it with sudo make install.
Compatibility: Pretty much anything you’ve got. It runs on X11, wayland or on nothing at all.
How to use it: Run “llamamp /path/to/song.ogg” or use the playlist.


Where’s the code?
The download link goes to gitlab, you can cut off the end to go to the source.
The gitlab repo appears to be a dump of random small .c programs and different .tar.gz archives. The download link OP provided is the source.
Oh. I was a bit confused at the names of the files, but now it makes sense.