My solution attempt to "Roulette"

[iampi31415]

Playground 1

I removed the MCU specifics to make it run in the playground; could also abstract Matrix LED dimensions to support any sequence. I removed the loop {} so it does not loop forever on the playground / tests.

Anyways, here is one version with comments:

use std::thread::sleep;
use std::time::Duration;

/// Move around in the 2D grid of LEDs.
enum Direction {
    Left,
    Right,
    Up,
    Down,
}
use Direction::{Down, Left, Right, Up}; // easier to type

/// This encapsulates moving towards right/left ...
/// And allows repeating the movement (or None, no movement.)
struct Towards {
    direction: Option<Direction>,
    steps: u8,
}
impl Towards {
    fn new(direction: Option<Direction>, steps: u8) -> Self {
        Self { direction, steps }
    }
    /// Panics if update leaves it Out of LED Matrix range.
    fn update_coords(&self, coords: &mut (usize, usize)) {
        match self.direction {
            Some(Left) if coords.0 > 0 => coords.0 -= 1,
            Some(Right) if coords.0 < 4 => coords.0 += 1,
            Some(Down) if coords.1 < 4 => coords.1 += 1,
            Some(Up) if coords.1 > 0 => coords.1 -= 1,
            None => (), // no changes
            _ => panic!("New value falls outside the led matrix range."),
        };
    }
}

fn main() {
    #[rustfmt::skip]
    let mut leds = [
        [0, 0, 0, 0, 0],
        [0, 0, 0, 0, 0],
        [0, 0, 0, 0, 0],
        [0, 0, 0, 0, 0],
        [0, 0, 0, 0, 0],
    ];
    let steps = 4;
    let delay_ms: u64 = 200;
    #[rustfmt::skip]
    let sequence = [ // how the light "moves"
        Towards::new(None, 1),
        Towards::new(Some(Right), steps),
        Towards::new(Some(Down), steps),
        Towards::new(Some(Left), steps),
        Towards::new(Some(Up), steps)
    ];

    let coords = &mut (0usize, 0usize); // usize allows array-indexing.

    for towards in sequence.iter() {
        for _ in 0..towards.steps {
            leds[coords.0][coords.1] = 0;
            towards.update_coords(coords);
            leds[coords.0][coords.1] = 1;
            println!("Current Position {coords:?}");
            sleep(Duration::from_millis(delay_ms))
        }
    }
}

[BartMassey]

i like your program style a lot: good use of Rust data representations to keep things clear and brief.

Thanks for sharing this!

[iampi31415]

Cheers!