Piston – A modular game engine written in Rust
I'm currently learning rust and it's an interesting experience dealing with libraries where I can't judge which parts of libraries are typical rust and which parts are just design decisions by the library developer.Since Rust is so new, perhaps there is no real difference, but the piston example shows some ideas that I'm not sure I like but I also don't know if that is just how things are done in the Rust world.    let window: PistonWindow = 
        WindowSettings::new("Hello Piston!", [640, 480])
        .exit_on_esc(true).build().unwrap();
    for e in window {
        e.draw_2d(|c, g| {
            clear([1.0; 4], g);
            rectangle([1.0, 0.0, 0.0, 1.0], // red
                      [0.0, 0.0, 100.0, 100.0],
                      c.transform, g);
        });
    }

That's iterating on a window which seems an odd choice.  
The functions clear and rectangle seem to me to be things that should be in traits rather than functions that require a parameter to say what the target of the drawing function is.