Comment by mattparas

Yep - you can write standalone steel code without interacting with Rust at all, just interacting with the interpreter. I've done the first few days of the advent of code in Steel without needing to touch any Rust. Now, I will say that Steel has gotten visibility faster than I've been able to keep up with, so you might find a native function missing, or something that you would like to use that isn't implemented yet - at which point you either need to implement it yourself or open up an issue for someone to get to :)