size.scss

//---------------------------
// Size function
// =============
// The size function returns a measurement determined by
// the (required) argument of level.
//
// Example: size(5);
// This will return 16rem.
//---------------------------
$__size-default: 2;
$__size-unit:    1rem;
@function size($level: 1) {
  @if $level <= 8 {
    $value: $level;
    @if $level == 1 {
      $value: half($__size-default);
    } @else {
      $value: power($__size-default, ($level + 1));
    }
    @return ($value * $__size-unit);
  } @else {
    @warn "Size ranges from 1–8. You provided #{level}."
  }
}