Macro step 

macro_rules! step {
    ($text:literal) => { ... };
    (fg=$fg:literal, $text:literal) => { ... };
    (bg=$bg:expr, fg=$fg:expr, $text:literal) => { ... };
    (length=$length:literal, $text:expr) => { ... };
    (bg=$bg:expr, fg=$fg:expr, length=$length:literal, $text:expr) => { ... };
    (length=$length:literal, $text:literal, $( $arg:expr ),* $(,)? ) => { ... };
    () => { ... };
}