Mixins in scss styles

_mixins.scss

@mixin flex($dir: row, $justify: start, $align: start, $wrap: wrap) {
  display: flex;
  @if $dir != row {
    flex-direction: $dir;
  }
  @if $wrap != wrap {
    flex-wrap: $wrap;
  }
  @if $justify != start {
    justify-content: $justify;
  }
  @if $align != start {
    align-items: $align;
  }
}