"The Rules of Crust
Every function is unsafe. No references, only pointers. No cargo, build with rustc directly. No std, but libc is allowed. Only Edition 2021. All user structs and enums #[derive(Clone, Copy)]. Everything is pub by default."
The least recreational languages are probably like Java,C#
He doesn't actually use rust "idiomatically". He calls this "crust":
1. Every function is unsafe
2. No references, only pointers
3. No cargo, just rustc
4. No std, only libc
...
I don't know if he is sticking to these rules throughout but that was the idea in the beginning of this project.