ascii donuts art in rust

main.rs
use std::{io::{stdout, Write}, thread, time::Duration};

fn main() {
    let donut_width = 50;
    let donut_height = 25;
    let donut_chars = vec![
        ' ', '.', '`', ',', ':', ';', 'i', 'l', '!', 'i', 'l', ':', ';', ':', '.', ',', '\'',
        '.',
    ];
    let donut_radius1 = 1.0;
    let donut_radius2 = 2.0;
    let mut a1 = 0.0;
    let mut a2 = 0.0;
    let mut output = String::new();
    loop {
        output.clear();
        for j in 0..donut_height {
            for i in 0..donut_width {
                let x = (i as f64 - donut_width as f64 / 2.0) / (donut_width as f64 / 2.0);
                let y = (j as f64 - donut_height as f64 / 2.0) / (donut_height as f64 / 2.0);
                let mut z = 0.0;
                z += (donut_radius1.powi(2) - x.powi(2) - y.powi(2)).sqrt();
                let r2 = donut_radius2.powi(2);
                let x2 = x * (a1 as f64).cos() - y * (a1 as f64).sin();
                let y2 = x * (a1 as f64).sin() + y * (a1 as f64).cos();
                z += (r2 - x2.powi(2) - y2.powi(2) - (a2 as f64).sin()).sqrt();
                let index = ((z * donut_chars.len() as f64) / 3.0).round() as usize;
                output.push(donut_chars[index]);
            }
            output.push('\n');
        }
        print!("{esc}[2J{esc}[1;1H", esc = 27 as char);
        print!("{}", output);
        stdout().flush().unwrap();
        a1 += 0.07;
        a2 += 0.03;
        thread::sleep(Duration::from_millis(50));
    }
}
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