Solution for discovery/microbit roulette challenge ( https://docs.rust-embedded.org/discovery/microbit/05-led-roulette/the-challenge.html ); It is able to rotate any matrix passed as parameter;

05-led-roulette.rs

#![deny(unsafe_code)]
#![no_main]
#![no_std]

use cortex_m_rt::entry;
use microbit::{
    board::Board,
    display::blocking::Display,
    hal::{prelude::*, Timer},
};
use panic_rtt_target as _;
use rtt_target::rtt_init_print;

fn rotate(roulette: &mut [[u8; 5]; 5]) {
    let mut left = 0;
    let mut right = roulette[0].len() - 1;
    let mut top = 0;
    let mut bottom = roulette.len() - 1;

    let mut prev;
    let mut cur;

    while left < right && top < bottom {
        prev = roulette[top + 1][left];

        for n in left..=right {
            cur = roulette[top][n];
            roulette[top][n] = prev;
            prev = cur;
        }

        top += 1;

        for n in top..=bottom {
            cur = roulette[n][right];
            roulette[n][right] = prev;
            prev = cur;
        }

        right -= 1;
        for n in (left..=right).rev() {
            cur = roulette[bottom][n];
            roulette[bottom][n] = prev;
            prev = cur;
        }

        bottom -= 1;
        for n in (top..=bottom).rev() {
            cur = roulette[n][left];
            roulette[n][left] = prev;
            prev = cur;
        }

        left += 1;
    }
}

#[entry]
fn main() -> ! {
    rtt_init_print!();

    if let Some(board) = Board::take() {
        let mut timer = Timer::new(board.TIMER0);
        let mut display = Display::new(board.display_pins);

        let mut roulette = [
            [1u8, 0, 0, 0, 0],
            [0, 0, 0, 0, 0],
            [0, 0, 0, 0, 0],
            [0, 0, 0, 0, 0],
            [0, 0, 0, 0, 0],
        ];
        loop {
            display.show(&mut timer, roulette, 100);
            display.clear();
            rotate(&mut roulette);
        }
    }

    panic!("never reached");
}