fn palindrome(text: Span<u8>) -> Bool {
    var left: usize = 0
    var right: usize = std.mem.len(text) - 1
    while left < right {
        if text[left] != text[right] {
            return false
        }
        left = left + 1
        right = right - 1
    }
    return true
}

pub fn main(world: World) -> Void raises {
    if palindrome(std.mem.span("level")) {
        check world.out.write("eertree ok\n")
    }
}