termion 1.5.6

extern crate termion;

use termion::event::Key;
use termion::input::TermRead;
use termion::raw::IntoRawMode;
use std::io::{Write, stdout, stdin};

fn rainbow<W: Write>(stdout: &mut W, blue: u8) {
    write!(stdout,
           "{}{}",
           termion::cursor::Goto(1, 1),
           termion::clear::All)
            .unwrap();

    for red in 0..32 {
        let red = red * 8;
        for green in 0..64 {
            let green = green * 4;
            write!(stdout,
                   "{} ",
                   termion::color::Bg(termion::color::Rgb(red, green, blue)))
                    .unwrap();
        }
        write!(stdout, "\n\r").unwrap();
    }

    writeln!(stdout, "{}b = {}", termion::style::Reset, blue).unwrap();
}

fn main() {
    let stdin = stdin();
    let mut stdout = stdout().into_raw_mode().unwrap();

    writeln!(stdout,
             "{}{}{}Use the up/down arrow keys to change the blue in the rainbow.",
             termion::clear::All,
             termion::cursor::Goto(1, 1),
             termion::cursor::Hide)
            .unwrap();

    let mut blue = 172u8;

    for c in stdin.keys() {
        match c.unwrap() {
            Key::Up => {
                blue = blue.saturating_add(4);
                rainbow(&mut stdout, blue);
            }
            Key::Down => {
                blue = blue.saturating_sub(4);
                rainbow(&mut stdout, blue);
            }
            Key::Char('q') => break,
            _ => {}
        }
        stdout.flush().unwrap();
    }

    write!(stdout, "{}", termion::cursor::Show).unwrap();
}