twbs--bootstrap/less/mixins/media-queries.less

// Media query mixins

.media-xs(@rules) {
  @media (max-width: @screen-xs-max) { @rules(); }
}

.media-sm(@rules) {
  @media (min-width: @screen-sm-min) { @rules(); }
}

.media-sm-max(@rules) {
  @media (min-width: @screen-sm-min) and (max-width: @screen-sm-max) { @rules(); }
}

.media-md(@rules) {
  @media (min-width: @screen-md-min) { @rules(); }
}

.media-md-max(@rules) {
  @media (min-width: @screen-md-min) and (max-width: @screen-md-max) { @rules(); }
}

.media-lg(@rules) {
  @media (min-width: @screen-lg-min) { @rules(); }
}