<===> input.scss
.simple {
  one-digit: U+1;
  four-digit: U+1234;
  six-digit: U+123456;
  hex-digit: U+1A2B;
  lowercase: u+1a2b;
}

<===> output.css
.simple {
  one-digit: U+1;
  four-digit: U+1234;
  six-digit: U+123456;
  hex-digit: U+1A2B;
  lowercase: u+1a2b;
}