Practice/_src/common/scss/_function.scss

@function color-yiq($color, $dark: #212529, $light: #fff) {
  $r: red($color);
  $g: green($color);
  $b: blue($color);

  $yiq: (($r * 299) + ($g * 587) + ($b * 114)) / 1000;

  @if ($yiq >= 150) {
    @return #343a40;
  } @else {
    @return #f8f9fa;
  }
}

@function REM($pxSize:16px){
  $remSize : $pxSize / $font-size-base !global;
  @return #{$remSize}rem;
}