Generated by SassMeister.com.

SassMeister-input.scss

// ----
// Sass (v3.4.9)
// Compass (v1.0.1)
// ----

// ==========================================================================
// Breakpoint Mixin
// ==========================================================================

$breakpoints: 320px, 600px, 900px;

@mixin breakpoint( $size ){
	@if type-of($size) == string {
	  $approved-value: 0;
		@each $breakpoint in $breakpoints {
			$and-larger: ">" + $breakpoint;
			$and-smaller: "<" + $breakpoint;

			@if $size == $and-smaller {
				$approved-value: 1;
				@media ( max-width: $breakpoint ) {
					@content;
					value: $and-smaller;
					true: $approved-value;
				}
			}
			@else {
				@if $size == $and-larger {
					$approved-value: 2;
					@media ( min-width: $breakpoint + 1 ) {
						@content;
						value: $and-larger;
						true: $approved-value;
					}
				}
				@else {
					@each $breakpoint-end in $breakpoints {
						$range: $breakpoint + "-" + $breakpoint-end;
						@if $size == $range {
							$approved-value: 3;
							@media ( min-width: $breakpoint + 1 ) and ( max-width: $breakpoint-end ) {
								@content;
								value: $range;
								true: $approved-value;
							}
						}
					}
				}
			}
		}
		@if $approved-value == 0 {
		  $sizes: "";
		  @each $breakpoint in $breakpoints {
		    $sizes: $sizes + " " + $breakpoint;
		  }
		  @error "ERROR in breakpoint( #{ $size } ): You can only use these sizes[ #{$sizes} ] using the following syntax [ <#{ nth( $breakpoints, 1 ) } >#{ nth( $breakpoints, 1 ) } #{ nth( $breakpoints, 1 ) }-#{ nth( $breakpoints, 2 ) } ]";
		}
	}
	@else {
	  $sizes: "";
		@each $breakpoint in $breakpoints {
		  $sizes: $sizes + " " + $breakpoint;
		}
		@error "ERROR in breakpoint( #{ $size } ): Please wrap the breakpoint $size in parenthesis. You can use these sizes[ #{$sizes} ] using the following syntax [ <#{ nth( $breakpoints, 1 ) } >#{ nth( $breakpoints, 1 ) } #{ nth( $breakpoints, 1 ) }-#{ nth( $breakpoints, 2 ) } ]";
	}
}

body {
  @include breakpoint( "<320px" ){
    // content
  }
  @include breakpoint( "<600px" ){
    // content
  }
  @include breakpoint( "<900px" ){
    // content
  }
  @include breakpoint( ">320px" ){
    // content
  }
  @include breakpoint( ">600px" ){
    // content
  }
  @include breakpoint( ">900px" ){
    // content
  }
  @include breakpoint( "320px-900px" ){
    // content
  }
  // @include breakpoint( "320pcsadfx-905px" ){
    // uncomment to throw syntax error
  // }
  // @include breakpoint( 320px ){
    // uncomment to throw string error
  // }
}

SassMeister-output.css

@media (max-width: 320px) {
  body {
    value: "<320px";
    true: 1;
  }
}
@media (max-width: 600px) {
  body {
    value: "<600px";
    true: 1;
  }
}
@media (max-width: 900px) {
  body {
    value: "<900px";
    true: 1;
  }
}
@media (min-width: 321px) {
  body {
    value: ">320px";
    true: 2;
  }
}
@media (min-width: 601px) {
  body {
    value: ">600px";
    true: 2;
  }
}
@media (min-width: 901px) {
  body {
    value: ">900px";
    true: 2;
  }
}
@media (min-width: 321px) and (max-width: 900px) {
  body {
    value: "320px-900px";
    true: 3;
  }
}