Generated by SassMeister.com. Example of @extending into classes instead of nested media queries.

SassMeister-input.scss

// ----
// libsass (v3.2.5)
// ----

$doc-font-size: 16; /* 16px */
$lap: 600;
$desk: 900;

@mixin mq($point, $constraint: min, $feature: width) {
	@media screen and (#{$constraint}-#{$feature}: $point / $doc-font-size + em) {
		@content;
	}
}


.media-wrap--3-2 {
	padding-top: 66.66%;
}

.media-wrap--letterbox {
  padding-top: 66.66%;
  
  @include mq($lap) {
  	padding-top: 25%;
  }
}


.module-info__media-wrap {
	@extend .media-wrap--3-2;
}

.module-promo__media-wrap {
	@extend .media-wrap--letterbox;
}

SassMeister-output.css

/* 16px */
.media-wrap--3-2, .module-info__media-wrap {
  padding-top: 66.66%;
}

.media-wrap--letterbox, .module-promo__media-wrap {
  padding-top: 66.66%;
}

@media screen and (min-width: 37.5em) {
  .media-wrap--letterbox, .module-promo__media-wrap {
    padding-top: 25%;
  }
}