$breakpoints: () !default

@function breakpoint($max-width: false, $min-width: false, $columns: false, $fallback-width: false)

$breakpoint: ()
@if $columns
  $breakpoint: join($breakpoint, columns $columns)
@if $fallback-width
  $breakpoint: join($breakpoint, fallback-width $fallback-width)
@if $max-width
  $breakpoint: join($breakpoint, max-width $max-width)
@if $min-width
  $breakpoint: join($breakpoint, min-width $min-width)

$breakpoints: append($breakpoints, $breakpoint)
@return $breakpoint