/* Dropdown navigation. Scoped to the site header and the mobile drawer
   so lesson pages cannot restyle the menu, and the menu cannot restyle lessons.
   Anchor targets use scroll-margin so #sections land below the sticky header. */

header.site,
nav.mobile-nav {
  --nav-panel: #ffffff;
  --nav-panel-border: var(--line, #e3e7ee);
  --nav-panel-hover: #f3f6fa;
  --nav-foot: #f4f7fb;
  --nav-muted: #3e4c5e;
  --nav-shadow: 0 18px 40px rgba(16, 24, 40, 0.16);
  --nav-header-offset: 78px;
}

html[data-theme="dark"] header.site,
html[data-theme="dark"] nav.mobile-nav {
  --nav-panel: #111A2E;
  --nav-panel-border: #26344F;
  --nav-panel-hover: #17243C;
  --nav-foot: #0E1628;
  --nav-muted: #d5deea;
  --nav-shadow: 0 24px 60px rgba(0, 0, 0, 0.55);
}

/* Category and directory anchors clear the sticky header (header height + 16px). */
.lesson-category,
#quality-improvement-basics,
#data-analysis-basics,
#lean-six-sigma-tools,
#excel-and-power-bi-skills,
#statistics-for-decision-making,
#exam-cssbb, #exam-cqe, #exam-mbb, #exam-cssgb, #exam-cmq, #exam-cre, #exam-pmp, #exam-nppe, #exam-cqa,
#my-exams,
#materials-quality, #material-specification-lookup, #steel-phase-explorer,
#engineering-calculators, #converters, #suggest-a-tool,
#corporate-training, #one-on-one-coaching, #consulting-support, #custom-lessons, #data-dashboard-support {
  scroll-margin-top: 108px;
}

header.site nav.desktop-nav {
  position: relative;
  align-items: center;
  gap: 0;
}

header.site nav.desktop-nav .nav-item {
  position: relative;
  display: flex;
  align-items: center;
}

header.site nav.desktop-nav .nav-tab-link {
  padding: 12px 0 12px 10px;
  border-bottom: 2px solid transparent;
  color: var(--ink);
  font-family: "Work Sans", Arial, sans-serif;
  font-size: 15px;
  font-weight: 600;
  line-height: 1.2;
  white-space: nowrap;
}

header.site nav.desktop-nav .nav-tab-link:hover,
header.site nav.desktop-nav .nav-tab-link[aria-current="page"] {
  color: var(--teal);
  border-bottom-color: var(--teal);
}

header.site nav.desktop-nav .nav-chevron {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  width: 28px;
  height: 36px;
  margin: 0 2px 0 0;
  padding: 0;
  border: 0;
  border-radius: 8px;
  background: transparent;
  color: var(--ink);
  cursor: pointer;
}

header.site nav.desktop-nav .nav-chevron:hover,
header.site nav.desktop-nav .nav-item.is-open .nav-chevron {
  background: var(--nav-panel-hover);
  color: var(--teal);
}

header.site nav.desktop-nav .nav-item.is-open .nav-chevron-icon {
  transform: rotate(180deg);
}

header.site nav.desktop-nav .nav-panel[hidden] {
  display: none !important;
}

header.site nav.desktop-nav .nav-panel {
  position: absolute;
  z-index: 40;
  top: calc(100% - 2px);
  left: -16px;
  width: 390px;
  padding: 0;
  border: 1px solid var(--nav-panel-border);
  border-radius: 14px;
  background: var(--nav-panel);
  box-shadow: var(--nav-shadow);
  color: var(--ink);
}

header.site nav.desktop-nav .nav-item-wide .nav-panel {
  width: 420px;
}

header.site nav.desktop-nav .nav-item[data-nav-item="about"] .nav-panel {
  left: auto;
  right: 0;
}

header.site nav.desktop-nav .nav-panel-head {
  display: flex;
  align-items: baseline;
  justify-content: space-between;
  gap: 12px;
  padding: 16px 20px 8px;
  color: var(--nav-muted);
  font-size: 12px;
  font-weight: 700;
  letter-spacing: 0.08em;
  text-transform: uppercase;
}

header.site nav.desktop-nav .nav-panel-head [data-nav-total] {
  font-size: 13px;
  font-weight: 600;
  letter-spacing: 0;
  text-transform: none;
}

header.site nav.desktop-nav .nav-rows {
  display: flex;
  flex-direction: column;
  padding: 4px 8px 8px;
}

header.site nav.desktop-nav .nav-panel a,
header.site nav.desktop-nav .nav-panel .nav-row {
  display: flex;
  align-items: center;
  gap: 10px;
  margin: 0;
  padding: 10px 12px;
  border: 0;
  border-bottom: 0;
  border-radius: 10px;
  color: var(--ink);
  font-size: 15px;
  font-weight: 500;
  line-height: 1.35;
  text-align: left;
  white-space: normal;
}

header.site nav.desktop-nav .nav-panel a:hover,
header.site nav.desktop-nav .nav-panel a:focus-visible {
  background: var(--nav-panel-hover);
  color: var(--ink);
  border-bottom-color: transparent;
}

header.site nav.desktop-nav .nav-name { flex: 1; min-width: 0; }

header.site nav.desktop-nav .nav-count,
header.site nav.desktop-nav .nav-desc,
header.site nav.desktop-nav .nav-soon {
  color: var(--nav-muted);
  font-size: 13px;
  font-weight: 600;
}

header.site nav.desktop-nav .nav-rich {
  align-items: flex-start;
  flex-direction: column;
  gap: 2px;
}

header.site nav.desktop-nav .nav-exam .nav-acronym {
  flex: 0 0 64px;
  color: var(--teal);
  font-weight: 700;
}

header.site nav.desktop-nav .nav-soon,
nav.mobile-nav .nav-soon {
  flex: none;
  padding: 2px 7px;
  border: 1px solid var(--nav-panel-border);
  border-radius: 999px;
  font-size: 11px;
  font-weight: 700;
  line-height: 1.3;
}

header.site nav.desktop-nav .is-soon {
  cursor: default;
  opacity: 0.72;
}

header.site nav.desktop-nav .nav-foot {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 12px;
  padding: 14px 20px;
  border-top: 1px solid var(--nav-panel-border);
  border-radius: 0 0 14px 14px;
  background: var(--nav-foot);
}

header.site nav.desktop-nav .nav-foot a {
  padding: 0;
  border: 0;
  background: transparent;
  font-size: 14px;
}

header.site nav.desktop-nav .nav-foot-primary {
  color: var(--teal);
  font-weight: 700;
}

header.site nav.desktop-nav .nav-foot-secondary {
  color: var(--nav-muted);
  font-weight: 600;
}

header.site nav.desktop-nav .nav-foot-primary:hover,
header.site nav.desktop-nav .nav-foot-secondary:hover {
  background: transparent;
}

header.site nav.desktop-nav .nav-book {
  display: block;
  width: 100%;
  padding: 12px 16px;
  border-radius: 10px;
  background: #0e7490;
  color: #ffffff;
  font-weight: 700;
  text-align: center;
}

header.site nav.desktop-nav .nav-book:hover {
  background: #0a5a70;
  color: #ffffff;
}

header.site nav.desktop-nav .nav-foot-solo {
  display: block;
}

@media (prefers-reduced-motion: no-preference) {
  header.site nav.desktop-nav .nav-panel:not([hidden]) {
    animation: nav-panel-in 140ms ease;
  }
  header.site nav.desktop-nav .nav-chevron-icon {
    transition: transform 140ms ease;
  }
}

@keyframes nav-panel-in {
  from { opacity: 0; transform: translateY(-4px); }
  to { opacity: 1; transform: none; }
}

/* Mobile drawer: the existing checkbox hamburger still opens it. */
@media (max-width: 1440px) {
  nav.mobile-nav[data-nav-root="mobile"] {
    position: fixed;
    z-index: 40;
    top: 0;
    right: 0;
    bottom: 0;
    left: 0;
    display: none;
    flex-direction: column;
    overflow: auto;
    border-bottom: 0;
    background: var(--paper, #fff);
    color: var(--ink);
  }

  .mnav-check:checked ~ nav.mobile-nav[data-nav-root="mobile"] {
    display: flex;
    padding-top: var(--nav-header-offset);
  }

  /* Header stays above the drawer so the close control remains reachable
     and page content cannot show through above the menu. */
  body.nav-drawer-open header.site,
  body:has(.mnav-check:checked) header.site {
    z-index: 50;
    background: var(--paper, #fff);
  }

  body.nav-drawer-open,
  body:has(.mnav-check:checked) {
    overflow: hidden;
  }
}

nav.mobile-nav .nav-acc-btn {
  display: flex;
  align-items: center;
  justify-content: space-between;
  width: 100%;
  min-height: 50px;
  padding: 0 16px;
  border: 0;
  border-bottom: 1px solid var(--line, #e3e7ee);
  background: transparent;
  color: var(--ink);
  font-family: "Work Sans", Arial, sans-serif;
  font-size: 15px;
  font-weight: 600;
  text-align: left;
  cursor: pointer;
}

nav.mobile-nav .nav-acc-btn[aria-current="page"] {
  color: var(--teal);
}

nav.mobile-nav .nav-acc.is-open .nav-chevron-icon {
  transform: rotate(180deg);
}

nav.mobile-nav .nav-acc-panel[hidden] {
  display: none !important;
}

nav.mobile-nav .nav-acc-panel {
  display: flex;
  flex-direction: column;
  padding: 4px 0 8px;
  background: var(--nav-panel-hover);
}

nav.mobile-nav .nav-acc-panel a,
nav.mobile-nav .nav-acc-panel .nav-row {
  display: flex;
  align-items: center;
  gap: 8px;
  min-height: 40px;
  margin: 0 12px 0 16px;
  padding: 8px 12px 8px 12px;
  border: 0;
  border-bottom: 0;
  border-left: 2px solid var(--teal);
  color: var(--ink);
  font-size: 15px;
  font-weight: 500;
}

nav.mobile-nav .nav-acc-panel a.nav-acc-all,
nav.mobile-nav .nav-acc-panel a.nav-book {
  font-weight: 700;
  color: var(--teal);
}

nav.mobile-nav .nav-acc-panel .nav-rich {
  align-items: flex-start;
  flex-direction: column;
  gap: 2px;
  min-height: 44px;
}

nav.mobile-nav .nav-desc,
nav.mobile-nav .nav-count {
  color: var(--nav-muted);
  font-size: 13px;
  font-weight: 600;
}

nav.mobile-nav .nav-acronym {
  flex: 0 0 64px;
  color: var(--teal);
  font-weight: 700;
}

nav.mobile-nav .nav-name { flex: 1; }

nav.mobile-nav .nav-drawer-footer {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 8px;
  margin-top: auto;
  position: sticky;
  bottom: 0;
  padding: 12px;
  border-top: 1px solid var(--line, #e3e7ee);
  background: var(--nav-foot);
}

nav.mobile-nav .nav-drawer-footer a {
  display: flex;
  align-items: center;
  justify-content: center;
  min-height: 44px;
  padding: 10px 12px;
  border: 1px solid var(--line, #e3e7ee);
  border-radius: 10px;
  background: var(--card, #fff);
  color: var(--ink);
  font-size: 14px;
  font-weight: 700;
  text-align: center;
}

nav.mobile-nav .nav-drawer-browse {
  border-color: transparent;
  background: #0e7490;
  color: #ffffff;
}

nav.mobile-nav .nav-drawer-browse:hover {
  background: #0a5a70;
  color: #ffffff;
}

@media (prefers-reduced-motion: reduce) {
  header.site nav.desktop-nav .nav-panel:not([hidden]),
  header.site nav.desktop-nav .nav-chevron-icon,
  nav.mobile-nav .nav-chevron-icon {
    animation: none;
    transition: none;
  }
}