powellian

<style>
/* GMAIL 
======== */
 u + .body .gmail {
    }
/* Target all Gmail and Inbox versions (Webmail, iOS, Android). 
In order to implement this technique your markup must contain
1) A DOCTYPE.
2) A body with a class name (ie. “body”)
3) An element with a class name (ie. “gmail”) 

powellian

// map headings - h1/.h1 etc...
@each $heading,
$size in $mapHeadings {

  #{$heading},
  .#{$heading} {
    font-size: rem-calc($size);
    margin-top: 0;
    margin-bottom: calc(var(--common-size)/3);
  }

powellian

// https://dvcs.w3.org/hg/FXTF/raw-file/tip/filters/index.html 
//
// grayscale      ex: filter: grayscale(100%);
// sepia          ex: filter: sepia(100%);
// saturate       ex: filter: saturate(0%);
// hue-rotate     ex: filter: hue-rotate(45deg);
// invert         ex: filter: invert(100%);
// brightness     ex: filter: brightness(15%);
// contrast       ex: filter: contrast(200%);
// blur           ex: filter: blur(2px);