Susy's at-breakpoint
is really just a shortcut for the simplest mix/max media-queries. For more powerful media-queries, I recommend the breakpoint plugin. You can use that in conjunction with Susy's layout
mixin to re-create the at-breakpoint
effect:
@include breakpoint($your-advanced-media-queries) {
@include layout($your-desired-column-count) {
// your styles
}
}