/**
 * Формирует тень по дизайн-гайдам.
 */
@mixin box-shadow($key) {
  @if $key == 'z1' {
    box-shadow:
      0 0 4px rgba(0, 0, 0, 0.04),
      0 2px 4px rgba(0, 0, 0, 0.08);
  } @else if $key == 'z2' {
    box-shadow:
      0 0 4px rgba(0, 0, 0, 0.04),
      0 4px 8px rgba(0, 0, 0, 0.1);
  } @else if $key == 'z2-straight' {
    box-shadow: 0 0 15px rgba(0, 0, 0, 0.12);
  } @else if $key == 'z3' {
    box-shadow:
      0 8px 16px rgba(0, 0, 0, 0.08),
      0 0 4px rgba(0, 0, 0, 0.04);
  } @else if $key == 'z4' {
    box-shadow:
      0 0 4px rgba(0, 0, 0, 0.04),
      0 12px 30px rgba(0, 0, 0, 0.1);
  } @else {
    @warn 'No such shadow `#{$key}`.';
  }
}

@function get-box-shadow($key) {
  $result: none;

  @if $key == 'z1' {
    $result:
      0 0 4px rgba(0, 0, 0, 0.04),
      0 2px 4px rgba(0, 0, 0, 0.08);
  } @else if $key == 'z2' {
    $result:
      0 0 4px rgba(0, 0, 0, 0.04),
      0 4px 8px rgba(0, 0, 0, 0.1);
  } @else if $key == 'z2-straight' {
    $result: 0 0 15px rgba(0, 0, 0, 0.12);
  } @else if $key == 'z3' {
    $result:
      0 8px 16px rgba(0, 0, 0, 0.08),
      0 0 4px rgba(0, 0, 0, 0.04);
  } @else if $key == 'z4' {
    $result:
      0 0 4px rgba(0, 0, 0, 0.04),
      0 12px 30px rgba(0, 0, 0, 0.1);
  } @else {
    @warn 'No such shadow `#{$key}`.';
  }

  @return $result;
}