LESS conversion of the magnific popup SASS styles ( https://github.com/dimsemenov/Magnific-Popup )

magnific-popup.less

/* Magnific Popup CSS */

////////////////////////
//
// Contents:
//
// 1. Default Settings
// 2. General styles
//    - Transluscent overlay
//    - Containers, wrappers
//    - Cursors
//    - Helper classes
// 3. Appearance
//    - Preloader & text that displays error messages
//    - CSS reset for buttons
//    - Close icon
//    - "1 of X" counter
//    - Navigation (left/right) arrows
//    - Iframe content type styles
//    - Image content type styles
//    - Media query where size of arrows is reduced
//    - IE7 support
//
////////////////////////



////////////////////////
// 1. Default Settings
////////////////////////

@overlayColor:                   #0b0b0b;
@overlayOpacity:                 0.8;
@shadow:                         0 0 8px rgba(0, 0, 0, 0.6); // shadow on image or iframe
@popupPaddingLeft:               8px; // Padding from left and from right side
@popupPaddingLeftMobile:         6px; // Same as above, but is applied when width of window is less than 800px

@zIndexBase:                     1040; // Base z-index of popup
@includeArrows:                  true; // include styles for nav arrows
@controlsOpacity:                0.65;
@controlsColor:                  #FFF;
@innerCloseIconColor:            #333;
@controlsTextColor:              #CCC; // Color of preloader and "1 of X" indicator
@controlsTextColorHover:         #FFF;
@IE7support:                     true; // Very basic IE7 support

// Iframe-type options
@includeIframeType:              true;
@iframePaddingTop:               40px;
@iframeBackground:               #000;
@iframeMaxWidth:                 900px;
@iframeRatio:                    9/16;

// Image-type options
@includeImageType:               true;
@imageBackground:                #444;
@imagePaddingTop:                40px;
@imagePaddingBottom:             40px;
@includeMobileLayoutForImage:    true; // Removes paddings from top and bottom

// Image caption options
@captionTitleColor:              #F3F3F3;
@captionSubtitleColor:           #BDBDBD;

@import "settings";

////////////////////////
// 2. General styles
////////////////////////

// Transluscent overlay

.mfp-bg {
  top: 0;
  left: 0;
  width: 100%;
  height: 100%;
  z-index: @zIndexBase + 2;
  overflow: hidden;
  position: fixed;

  background: @overlayColor;
  opacity: @overlayOpacity;
  .a() when (@IE7support) { 
  	filter: ~"alpha(opacity=(@{overlayOpacity}*100))";
  }
  .a();
}

// Wrapper for popup
.mfp-wrap {
  top: 0;
  left: 0;
  width: 100%;
  height: 100%;
  z-index: @zIndexBase + 3;
  position: fixed;
  outline: none !important;
  -webkit-backface-visibility: hidden; // fixes webkit bug that can cause "false" scrollbar
}

// Root container
.mfp-container {
  text-align: center;
  position: absolute;
  width: 100%;
  height: 100%;
  left: 0;
  top: 0;
  padding: 0 @popupPaddingLeft;
  -webkit-box-sizing: border-box;
  -moz-box-sizing: border-box;
  box-sizing: border-box;
}

// Vertical centerer helper
.mfp-container:before {
  content: '';
  display: inline-block;
  height: 100%;
  vertical-align: middle;
}

// Remove vertical centering when popup has class `mfp-align-top`
.mfp-align-top .mfp-container:before {
  display: none;
}

// Popup content holder
.mfp-content {
  position: relative;
  display: inline-block;
  vertical-align: middle;
  margin: 0 auto;
  text-align: left;
  z-index: @zIndexBase + 5;
}
.mfp-inline-holder .mfp-content,
.mfp-ajax-holder .mfp-content {
  width: 100%;
  cursor: auto;
}

// Cursors
.mfp-ajax-cur {
  cursor: progress;
}
.mfp-zoom-out-cur,
.mfp-zoom-out-cur .mfp-image-holder .mfp-close {
  cursor: -moz-zoom-out;
  cursor: -webkit-zoom-out;
  cursor: zoom-out;
}
.mfp-zoom {
  cursor: pointer;
  cursor: -webkit-zoom-in;
  cursor: -moz-zoom-in;
  cursor: zoom-in;
}
.mfp-auto-cursor .mfp-content {
  cursor: auto;
}

.mfp-close,
.mfp-arrow,
.mfp-preloader,
.mfp-counter {
  -webkit-user-select:none;
  -moz-user-select: none;
  user-select: none;
}

// Hide the image during the loading
.mfp-loading.mfp-figure {
  display: none;
}

// Helper class that hides stuff
.mfp-hide {
  display: none !important;
}



////////////////////////
// 3. Appearance
////////////////////////

// Preloader and text that displays error messages
.mfp-preloader {
  color: @controlsTextColor;
  position: absolute;
  top: 50%;
  width: auto;
  text-align: center;
  margin-top: -0.8em;
  left: 8px;
  right: 8px;
  z-index: @zIndexBase + 4;
}
.mfp-preloader a {
  color: @controlsTextColor;
}
.mfp-preloader a:hover {
  color: @controlsTextColorHover;
}

// Hide preloader when content successfully loaded
.mfp-s-ready .mfp-preloader {
  display: none;
}

// Hide content when it was not loaded
.mfp-s-error .mfp-content {
  display: none;
}


// CSS-reset for buttons
button.mfp-close,
button.mfp-arrow {
  overflow: visible;
  cursor: pointer;
  background: transparent;
  border: 0;
  -webkit-appearance: none;
  display: block;
  padding: 0;
  z-index: @zIndexBase + 6;
}
button::-moz-focus-inner {
    padding: 0;
    border: 0
}


// Close icon
.mfp-close {
  width: 44px;
  height: 44px;
  line-height: 44px;

  position: absolute;
  right: 0;
  top: 0;
  text-decoration: none;
  text-align: center;
  opacity: @controlsOpacity;
  padding: 0 0 18px 10px;
  color: @controlsColor;

  font-style: normal;
  font-size: 28px;
  font-family: Arial, Baskerville, monospace;

  &:hover,
  &:focus {
    opacity: 1;
  }

  &:active {
    top: 1px;
  }
}
.mfp-close-btn-in .mfp-close {
  color: @innerCloseIconColor;
}
.mfp-image-holder .mfp-close,
.mfp-iframe-holder .mfp-close {
  color: @controlsColor;
  right: -6px;
  text-align: right;
  padding-right: 6px;
  width: 100%;
}

// "1 of X" counter
.mfp-counter {
  position: absolute;
  top: 0;
  right: 0;
  color: @controlsTextColor;
  font-size: 12px;
  line-height: 18px;
}

// Navigation arrows
.b() when (@includeArrows) {
  .mfp-arrow {
    position: absolute;
    opacity: @controlsOpacity;
    margin: 0;
    top: 50%;
    margin-top: -55px;
    padding: 0;
    width: 90px;
    height: 110px;
    -webkit-tap-highlight-color: rgba(0,0,0,0);
  }
  .mfp-arrow:active {
    margin-top: -54px;
  }
  .mfp-arrow:hover,
  .mfp-arrow:focus {
    opacity: 1;
  }

  .mfp-arrow {

    &:before,
    &:after,
    .mfp-b,
    .mfp-a {
      content: '';
      display: block;
      width: 0;
      height: 0;
      position: absolute;
      left: 0;
      top: 0;
      margin-top: 35px;
      margin-left: 35px;
      border: medium inset transparent;
    }

    &:after,
    .mfp-a {

      border-top-width: 13px;
      border-bottom-width: 13px;
      top:8px;
    }

    &:before,
    .mfp-b {
      border-top-width: 21px;
      border-bottom-width: 21px;
    }

  }

  .mfp-arrow-left {
    left: 0;

    &:after,
    .mfp-a {
      border-right: 17px solid #FFF;
      margin-left: 31px;
    }
    &:before,
    .mfp-b {
      margin-left: 25px;
      border-right: 27px solid #3f3f3f;
    }
  }

  .mfp-arrow-right {
    right: 0;
    &:after,
    .mfp-a {
      border-left: 17px solid #FFF;
      margin-left: 39px
    }
    &:before,
    .mfp-b {
      border-left: 27px solid #3f3f3f;
    }
  }
}
.b();



// Iframe content type
.c() when (@includeIframeType) {
  .mfp-iframe-holder {
    padding-top: @iframePaddingTop;
    padding-bottom: @iframePaddingTop;
  }
  .mfp-iframe-holder .mfp-content {
    line-height: 0;
    width: 100%;
    max-width: @iframeMaxWidth;
  }
  .mfp-iframe-scaler {
    width: 100%;
    height: 0;
    overflow: hidden;
    padding-top: @iframeRatio * 100%;
  }
  .mfp-iframe-scaler iframe {
    position: absolute;
    display: block;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
    box-shadow: @shadow;
    background: @iframeBackground;
  }
  .mfp-iframe-holder .mfp-close {
    top: -40px;
  }
}
.c();



// Image content type
.d() when (@includeImageType) {

  /* Main image in popup */
  img.mfp-img {
    width: auto;
    max-width: 100%;
    height: auto;
    display: block;
    line-height: 0;
    -webkit-box-sizing: border-box;
    -moz-box-sizing: border-box;
    box-sizing: border-box;
    padding: @imagePaddingTop 0 @imagePaddingBottom;
    margin: 0 auto;
  }

  /* The shadow behind the image */
  .mfp-figure:after {
    content: '';
    position: absolute;
    left: 0;
    top: @imagePaddingTop;
    bottom: @imagePaddingBottom;
    display: block;
    right: 0;
    width: auto;
    height: auto;
    z-index: -1;
    box-shadow: @shadow;
    background: @imageBackground;
  }
  .mfp-figure {
    line-height: 0;
  }
  .mfp-bottom-bar {
    margin-top:  -36px;
    position: absolute;
    top: 100%;
    left: 0;
    width: 100%;
    cursor: auto;
  }
  .mfp-title {
    text-align: left;
    line-height: 18px;
    color: @captionTitleColor;
    word-break: break-word;
    padding-right: 36px; // leave some space for counter at right side
  }

  .mfp-figure small {
    color: @captionSubtitleColor;
    display: block;
    font-size: 12px;
    line-height: 14px;
  }
  .mfp-image-holder .mfp-content {
    max-width: 100%;
  }

  .mfp-gallery .mfp-image-holder .mfp-figure {
    cursor: pointer;
  }

	.e() when (@includeMobileLayoutForImage) {

      @media screen and (max-width: 800px) and (orientation:landscape), screen and (max-height: 300px) {
        /**
         * Remove all paddings around the image on small screen
         */
        .mfp-img-mobile .mfp-image-holder {
          padding-left: 0;
          padding-right: 0;
        }
        .mfp-img-mobile img.mfp-img {
          padding: 0;
        }
        /* The shadow behind the image */
        .mfp-img-mobile .mfp-figure:after {
          top: 0;
          bottom: 0;
        }

        .mfp-img-mobile .mfp-bottom-bar {
          background: rgba(0,0,0,0.6);
          bottom: 0;
          margin: 0;
          top: auto;
          padding: 3px 5px;
          position: fixed;
          -webkit-box-sizing: border-box;
          -moz-box-sizing: border-box;
          box-sizing: border-box;
        }
        .mfp-img-mobile .mfp-bottom-bar:empty {
          padding: 0;
        }
        .mfp-img-mobile .mfp-counter {
          right: 5px;
          top: 3px;
        }
        .mfp-img-mobile .mfp-close {
          top: 0;
          right: 0;
          width: 35px;
          height: 35px;
          line-height: 35px;
          background: rgba(0, 0, 0, 0.6);
          position: fixed;
          text-align: center;
          padding: 0;
        }
        .mfp-img-mobile .mfp-figure small {
          display: inline;
          margin-left: 5px;
        }
      }
  }
  .e();

}
.d();



// Scale navigation arrows and reduce padding from sides
@media all and (max-width: 900px) {
  .mfp-arrow {
    -webkit-transform: scale(0.75);
    transform: scale(0.75);
  }
  .mfp-arrow-left {
    -webkit-transform-origin: 0;
    transform-origin: 0;
  }
  .mfp-arrow-right {
    -webkit-transform-origin: 100%;
    transform-origin: 100%;
  }
  .mfp-container {
    padding-left: @popupPaddingLeftMobile;
    padding-right: @popupPaddingLeftMobile;
  }
}



// IE7 support
// Styles that make popup look nicier in old IE
.f() when (@IE7support) {
  .mfp-ie7 {
    .mfp-img {
      padding: 0;
    }
    .mfp-bottom-bar {
      width: 600px;
      left: 50%;
      margin-left: -300px;
      margin-top: 5px;
      padding-bottom: 5px;
    }
    .mfp-container {
      padding: 0;
    }
    .mfp-content {
      padding-top: 44px;
    }
    .mfp-close {
      top: 0;
      right: 0;
      padding-top: 0;
    }
  }
}
.f();

Nice one. But what is @import "settings";?