I think this game would really benefit from being able to restart on the screen that you lost on. It's not all that exciting to play through a bunch of levels you've already beaten, especially as the early levels are pretty simple & similar to each other.
I think there's enough meat in terms of the actual execution that re-trying a level would not get too boring too quickly. (That is, I could easily see myself failing a more-difficult level multiple times in a row, even if I was able to quickly restart it).
Besides that, I quite like this. It's like an action puzzle game that resembles a programming puzzle game, something I haven't quite seen before. And, always fun to see games written in Rust. :)