header.css

/**
 * @file
 * Header region styling.
 */
@media (min-width: 34em) {
  .l-header-inner {
    min-height: 6.125rem;
  }
}

.l-header a {
  -webkit-transition: background-color 0.25s ease-out;
  transition: background-color 0.25s ease-out;
}

.header-identity-wrapper:after {
  /* Clearfix */
  content: '';
  display: table;
  clear: both;
}
.header-identity-wrapper strong {
  font-weight: inherit;
}

@media (min-width: 48em) {
  .header-identity-wrapper {
    display: block;
    float: left;
  }

  [dir="rtl"] .header-identity-wrapper {
    float: right;
  }
}

.header-site-name-wrapper {
  margin: 0;
  padding: 0;
  overflow-wrap: break-word;
}

@media (min-width: 34em) {
  .header-site-name-wrapper {
    float: left;
  }

  [dir="rtl"] .header-site-name-wrapper {
    float: right;
  }
}

.header-logo-wrapper {
  display: block;
  float: left;
}

[dir="rtl"] .header-logo-wrapper {
  float: right;
}

/* Makes sure images that are tall logos don't pop out of container */
.header-logo-tall img {
  width: auto;
  height: 100%;
}

.header-site-name-link {
  display: block;
  margin: 0;
}

.header-site-slogan {
  margin: 0;
}

.l-header .block-system-header .block-content:after {
  /* Clearfix header block */
  content: "";
  display: table;
  clear: both;
}

/**
 * Menus in header area
 */
.header-menu {
  clear: both;
}

.header-menu:after {
  /* Clearfix header menu */
  content: "";
  display: table;
  clear: both;
}

.header-menu > .links {
  /* Center menu at mobile */
  display: inline-block;
}

@media (min-width: 48em) {
  .header-menu {
    float: right;
    clear: none;
  }

  [dir="rtl"] .header-menu {
    float: left;
    clear: none;
  }
}

@media (min-width: 34em) {
  .l-header .block-system-main-menu {
    clear: both;
  }
}

.l-header .menu,
.l-header .menu li {
  list-style: none;
  margin: 0;
  padding: 0;
}

.l-header .menu:after {
  /* Clearfix menus */
  content: '';
  display: table;
  clear: both;
}

.l-header .menu > li,
.header-menu li {
  float: left;
}

[dir="rtl"] .l-header .menu > li,
[dir="rtl"] .header-menu li {
  float: right;
}

.l-header .menu a,
.header-menu a {
  display: block;
  padding: 1rem 1.25rem;
}
.l-header .menu-toggle-button {
  margin-left: .9375rem;
  padding: .5rem 0;
}
.l-header .menu-toggle-button-text {
  color: #bcbbbb;
}

@media (min-width: 34em) {
  /* Specific selector to avoid contextual links */
  .l-header .menu a,
  .header-menu a {
    padding: 1rem 1.25rem;
  }
}

@media (min-width: 48em) {
  .header-menu a {
    /* Attempt at lining up baseline of site name and header menu */
    padding-top: 1.9375rem;
    padding-bottom: 1.0625rem;
    line-height: 1.25rem;
  }
}

@media (min-width: 62em) {
  .header-menu a {
    /* Attempt at lining up baseline of site name and header menu */
    padding-top: 2rem;
    padding-bottom: 1rem;
    line-height: 1.25rem;
  }
}

.header-menu .links,
.header-menu li {
  margin: 0;
  padding: 0;
}

.header-menu .links li:before,
.header-menu .links li:after {
  /* Hides arrows intented for action links in body */
  display: none;
}