There is none.
Ok, ok, that's not entirely true.
But if you're looking for good code samples or tutorials, how to write your own raycaster, you should turn around and leave this place.
Go and download Wolfenstein 3D source code and spent some time analyzing it - much better idea than looking through these directories.
But if you still want to see what's in there, I can tell you: my playground.
For some time I am absolutely fascinated with ray casting and ray tracing.
My goal is to undesrtand basics behind those algorithms and then try to write something using just Vulkan.
So here's this little sandbox. Mainly coded in C and C++ but I tried myself with Fortran (don't ask me why...) and Rust (that was actually fun!). I did some coding for AVR and ARM too.
I used ncurses, SFML, my own OLED and LCD drivers to draw on screen, the next is SDL (I wanna try to write good C code for PC - I am ARM dev / Yocto Engineer on normal days).
So that's it. My little, fun side gig where I try to understand how did idSoftware write Wolfenstein 3D for 12 MHz 80286 :)