// Iterate over each key-val pair in the $headings map
@each $key, $value in $headings {
    // Define classes for each head
    .#{$key} {
        font-size: $value;
    }

    // Iterate over each bp_key-bp_val pair to generate color classes for each breakpoint
    @each  $bp_key, $bp_val in $breakpoints {
        @media (min-width: $bp_val) {
            // Define classes for each head
            .#{$bp_key}\:#{$key} {
                font-size: $value;
            }
        }
    }
}