$sm-range: (34rem, calc(48rem - 1px));
$md-range: (48rem, calc(62rem - 1px));
$lg-range: (62rem, calc(75rem - 1px));
$xl-range: 75rem;

$md-down: '#{$screen} and (max-width: #{upper-bound($md-range)})';
$lg-down: '#{$screen} and (max-width: #{upper-bound($lg-range)})';

$md-up: '#{$screen} and (min-width: #{lower-bound($md-range)})';
$lg-up: '#{$screen} and (min-width: #{lower-bound($lg-range)})';

$sm-only: '#{$screen} and (max-width: #{upper-bound($sm-range)})';
$md-only: '#{$screen} and (min-width: #{lower-bound($md-range)}) and (max-width: #{upper-bound($md-range)})';
$lg-only: '#{$screen} and (min-width: #{lower-bound($lg-range)}) and (max-width: #{upper-bound($lg-range)})';
$xl-only: '#{$screen} and (min-width: #{$xl-range})';