$small-break:  600px;
$medium-break: 800px;

@mixin small(){ // smaller than small-break
  @media screen and (max-width: $small-break) {
    @content;
  }
}
@mixin small-medium(){ // smaller than medium-break
  @media screen and (max-width: $medium-break) {
    @content;
  }
}
@mixin medium(){ // between small and medium-break
  @media screen and (min-width: $small-break) and (max-width: $medium-break) {
    @content;
  }
}
@mixin medium-large(){ // larger than small-break
  @media screen and (min-width: $small-break) {
    @content;
  }
}
@mixin large(){ // larger than medium-break
  @media screen and (min-width: $medium-break) {
    @content;
  }
}