:root {
  --studyos-nav-ink: #141a18;
  --studyos-nav-muted: rgba(20, 26, 24, 0.62);
  --studyos-nav-line: rgba(20, 26, 24, 0.12);
  --studyos-nav-panel: rgba(255, 255, 255, 0.88);
  --studyos-nav-panel-strong: rgba(255, 255, 255, 0.96);
  --studyos-nav-shadow: 0 18px 50px rgba(28, 38, 34, 0.12);
  --studyos-nav-ease: cubic-bezier(0.2, 0.8, 0.2, 1);
}

.studyos-nav-slot {
  position: relative;
  z-index: 80;
}

.studyos-top-nav {
  position: sticky;
  top: 12px;
  z-index: 80;
  width: 100%;
  color: var(--studyos-nav-ink);
}

.studyos-nav-shell {
  position: relative;
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 12px;
  min-height: 58px;
  padding: 8px 10px 8px 12px;
  border: 1px solid var(--studyos-nav-line);
  border-top-color: rgba(255, 255, 255, 0.82);
  border-radius: 24px;
  background: linear-gradient(180deg, rgba(255, 255, 255, 0.86), rgba(255, 255, 255, 0.68));
  box-shadow: var(--studyos-nav-shadow), inset 0 1px 0 rgba(255, 255, 255, 0.9);
  backdrop-filter: blur(22px) saturate(1.18);
  -webkit-backdrop-filter: blur(22px) saturate(1.18);
}

.studyos-nav-brand {
  display: inline-flex;
  align-items: center;
  gap: 9px;
  min-height: 40px;
  min-width: max-content;
  padding: 8px 10px;
  border-radius: 16px;
  font-weight: 760;
  letter-spacing: 0;
  color: var(--studyos-nav-ink);
}

.studyos-nav-mark {
  display: grid;
  width: 28px;
  height: 28px;
  place-items: center;
  border: 1px solid rgba(20, 26, 24, 0.12);
  border-radius: 10px;
  background: rgba(255, 255, 255, 0.72);
  color: #5c8b78;
  box-shadow: inset 0 1px 0 rgba(255, 255, 255, 0.92), 0 8px 18px rgba(48, 66, 58, 0.08);
}

.studyos-nav-center {
  position: relative;
  display: flex;
  align-items: center;
  justify-content: center;
  gap: 2px;
  min-width: 0;
}

.studyos-nav-orbit {
  position: absolute;
  top: 4px;
  left: 0;
  width: 0;
  height: calc(100% - 8px);
  border-radius: 999px;
  pointer-events: none;
  opacity: 0;
  background: rgba(255, 255, 255, 0.64);
  box-shadow: inset 0 1px 0 rgba(255, 255, 255, 0.88), 0 6px 20px rgba(35, 49, 43, 0.08);
  transition:
    opacity 180ms var(--studyos-nav-ease),
    transform 220ms var(--studyos-nav-ease),
    width 220ms var(--studyos-nav-ease);
}

.studyos-nav-link,
.studyos-nav-trigger {
  position: relative;
  z-index: 1;
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: 5px;
  min-height: 40px;
  padding: 9px 12px;
  border: 0;
  border-radius: 999px;
  color: var(--studyos-nav-muted);
  background: transparent;
  font: inherit;
  font-size: 14px;
  font-weight: 720;
  letter-spacing: 0;
  white-space: nowrap;
  cursor: pointer;
  transition: color 180ms var(--studyos-nav-ease), transform 180ms var(--studyos-nav-ease);
}

.studyos-nav-link::after,
.studyos-nav-trigger::after {
  content: "";
  position: absolute;
  left: 12px;
  right: 12px;
  bottom: 3px;
  height: 2px;
  border-radius: 999px;
  background: var(--studyos-nav-ink);
  transform: scaleX(0);
  transform-origin: center;
  transition: transform 220ms var(--studyos-nav-ease);
}

.studyos-nav-link:hover,
.studyos-nav-link:focus-visible,
.studyos-nav-link[aria-current="page"],
.studyos-nav-trigger:hover,
.studyos-nav-trigger:focus-visible,
.studyos-nav-trigger[aria-expanded="true"],
.studyos-nav-trigger[data-active="true"] {
  color: var(--studyos-nav-ink);
  outline: none;
}

.studyos-nav-link:hover::after,
.studyos-nav-link:focus-visible::after,
.studyos-nav-link[aria-current="page"]::after,
.studyos-nav-trigger:hover::after,
.studyos-nav-trigger:focus-visible::after,
.studyos-nav-trigger[aria-expanded="true"]::after,
.studyos-nav-trigger[data-active="true"]::after {
  transform: scaleX(1);
}

.studyos-nav-trigger:hover .studyos-chevron,
.studyos-nav-trigger:focus-visible .studyos-chevron {
  transform: translateY(-1px) rotate(45deg);
}

.studyos-nav-trigger[aria-expanded="true"] .studyos-chevron {
  transform: translateY(1px) rotate(-135deg);
}

.studyos-chevron {
  width: 7px;
  height: 7px;
  border-right: 1.6px solid currentColor;
  border-bottom: 1.6px solid currentColor;
  transform: translateY(-2px) rotate(45deg);
  transition: transform 240ms var(--studyos-nav-ease);
}

.studyos-nav-group {
  position: relative;
}

.studyos-drop-panel {
  position: absolute;
  top: calc(100% + 10px);
  left: 50%;
  min-width: 270px;
  max-width: min(360px, calc(100vw - 32px));
  padding: 10px;
  border: 1px solid rgba(20, 26, 24, 0.12);
  border-radius: 22px;
  background: var(--studyos-nav-panel-strong);
  box-shadow: 0 24px 68px rgba(28, 38, 34, 0.16), inset 0 1px 0 rgba(255, 255, 255, 0.94);
  opacity: 0;
  visibility: hidden;
  pointer-events: none;
  transform: translate(-50%, -6px) scale(0.98);
  transform-origin: top center;
  transition:
    opacity 220ms var(--studyos-nav-ease),
    transform 240ms var(--studyos-nav-ease);
  backdrop-filter: blur(18px) saturate(1.08);
  -webkit-backdrop-filter: blur(18px) saturate(1.08);
}

.studyos-nav-trigger[aria-expanded="true"] + .studyos-drop-panel {
  opacity: 1;
  visibility: visible;
  pointer-events: auto;
  transform: translate(-50%, 0) scale(1);
}

.studyos-drop-panel::before {
  content: "";
  position: absolute;
  top: -6px;
  left: 50%;
  width: 12px;
  height: 12px;
  border-left: 1px solid rgba(20, 26, 24, 0.1);
  border-top: 1px solid rgba(20, 26, 24, 0.1);
  background: var(--studyos-nav-panel-strong);
  transform: translateX(-50%) rotate(45deg);
}

.studyos-drop-panel a,
.studyos-drop-note {
  position: relative;
  display: block;
  width: 100%;
  padding: 11px 12px;
  border-radius: 15px;
  color: var(--studyos-nav-ink);
}

.studyos-drop-panel a {
  transition: background 160ms var(--studyos-nav-ease), transform 160ms var(--studyos-nav-ease);
}

.studyos-drop-panel a:hover,
.studyos-drop-panel a:focus-visible {
  background: rgba(244, 240, 231, 0.76);
  outline: none;
  transform: translateY(-1px);
}

.studyos-drop-panel b {
  display: block;
  font-size: 14px;
  line-height: 1.25;
}

.studyos-drop-panel small,
.studyos-drop-note small {
  display: block;
  margin-top: 4px;
  color: var(--studyos-nav-muted);
  font-size: 12px;
  line-height: 1.45;
}

.studyos-drop-note {
  color: rgba(20, 26, 24, 0.78);
  background: rgba(244, 240, 231, 0.42);
}

.studyos-mobile-menu-button {
  display: none;
  align-items: center;
  justify-content: center;
  gap: 8px;
  min-height: 40px;
  padding: 9px 12px;
  border: 1px solid rgba(20, 26, 24, 0.12);
  border-radius: 999px;
  color: var(--studyos-nav-ink);
  background: rgba(255, 255, 255, 0.72);
  font: inherit;
  font-weight: 740;
}

.studyos-mobile-panel {
  display: none;
}

@media (max-width: 980px) {
  .studyos-nav-shell {
    flex-wrap: wrap;
  }

  .studyos-nav-center {
    order: 3;
    width: 100%;
  }
}

@media (max-width: 760px) {
  .studyos-top-nav {
    top: 8px;
  }

  .studyos-nav-shell {
    border-radius: 20px;
  }

  .studyos-nav-center {
    display: none;
  }

  .studyos-mobile-menu-button {
    display: inline-flex;
  }

  .studyos-mobile-menu-button[aria-expanded="true"] .studyos-chevron {
    transform: translateY(1px) rotate(-135deg);
  }

  .studyos-mobile-panel {
    display: grid;
    width: 100%;
    max-height: 0;
    overflow: hidden;
    opacity: 0;
    gap: 8px;
    transition:
      max-height 260ms var(--studyos-nav-ease),
      opacity 220ms var(--studyos-nav-ease);
  }

  .studyos-top-nav[data-mobile-open="true"] .studyos-mobile-panel {
    max-height: 72vh;
    opacity: 1;
    overflow: auto;
    padding-top: 8px;
  }

  .studyos-mobile-row,
  .studyos-mobile-category {
    display: flex;
    align-items: center;
    justify-content: space-between;
    width: 100%;
    min-height: 44px;
    padding: 10px 12px;
    border: 1px solid rgba(20, 26, 24, 0.09);
    border-radius: 16px;
    color: var(--studyos-nav-ink);
    background: rgba(255, 255, 255, 0.66);
    font: inherit;
    font-weight: 730;
    text-align: left;
  }

  .studyos-mobile-group {
    display: grid;
    gap: 6px;
  }

  .studyos-mobile-submenu {
    display: none;
    gap: 6px;
    padding-left: 10px;
  }

  .studyos-mobile-group[data-open="true"] .studyos-mobile-submenu {
    display: grid;
  }

  .studyos-mobile-submenu a,
  .studyos-mobile-submenu span {
    display: block;
    padding: 10px 12px;
    border-radius: 14px;
    color: var(--studyos-nav-muted);
    background: rgba(255, 255, 255, 0.52);
    font-size: 14px;
  }
}

@media (prefers-reduced-motion: reduce) {
  .studyos-nav-orbit,
  .studyos-nav-link,
  .studyos-nav-trigger,
  .studyos-chevron,
  .studyos-drop-panel,
  .studyos-mobile-panel {
    transition: none;
  }
}