Thanks! It looks like I'm getting close. I'm pretty sure I needed to run
sudo cargo new gatchi --bin
before running
cargo run --release gatchi
and I needed to have its directory name in "snake-case".
I got
Compiling gatchi-same v0.1.0 (/[dir]/gatchi-same)
Finished release [optimized] target(s) in 0.28s
Running `target/release/gatchi-same gatchi`
Hello, world!
But I'm not playing yet