columns($span: $columns)¶ ↑
$n: nth($span, 1)
$parent-n: parent-columns($span)
$expression: "(100% + #{$gutter}) * #{$n / $parent-n} - #{$gutter}"
$fallback: ($fallback-width - $gutter) * $n / $columns - $gutter
+calc(width, $expression, $fallback)
@each $breakpoint in $breakpoints
+media($breakpoint)
$parent-n: parent-columns($span)
$expression: "(100% + #{$gutter}) * #{$n / $parent-n} - #{$gutter}"
$fallback: ($fallback-width - $gutter) * $n / $columns - $gutter
+calc(width, $expression, $fallback)
display: block
margin-right: $gutter
float: left