.dt-header {
  position: sticky;
  top: 0;
  z-index: 40;
  background-color: var(--color-surface);
  border-bottom: 1px solid var(--color-border-subtle);
  box-shadow: var(--shadow-subtle);
}

.dt-header__inner {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: var(--space-8);
  padding-top: var(--space-8);
  padding-bottom: var(--space-8);
}

.dt-header__brand {
  display: flex;
  align-items: center;
}

.dt-header__logo-link {
  display: inline-flex;
  align-items: center;
  gap: var(--space-6);
}

.dt-header__logo-mark {
  width: 40px;
  height: 40px;
  border-radius: var(--radius-lg);
  background: linear-gradient(135deg, var(--color-primary), var(--color-primary-strong));
  display: inline-flex;
  align-items: center;
  justify-content: center;
  box-shadow: var(--shadow-soft);
  color: #ffffff;
}

.dt-header__logo-icon {
  font-size: 1.1rem;
}

.dt-header__brand-text {
  display: flex;
  flex-direction: column;
}

.dt-header__site-name {
  font-weight: 600;
  font-size: var(--font-size-lg);
  letter-spacing: 0.01em;
  color: var(--gray-900);
}

.dt-header__site-tagline {
  font-size: var(--font-size-xs);
  color: var(--color-text-muted);
}

.dt-header__nav {
  margin-left: auto;
  display: block;
}

.dt-header__nav-list {
  list-style: none;
  display: flex;
  align-items: center;
  gap: var(--space-6);
}

.dt-header__nav-link {
  position: relative;
  display: inline-flex;
  align-items: center;
  padding: 0.35rem 0.25rem;
  font-size: var(--font-size-sm);
  font-weight: 500;
  color: var(--gray-700);
}

.dt-header__nav-link::after {
  content: "";
  position: absolute;
  left: 0;
  right: 0;
  bottom: 0;
  height: 2px;
  border-radius: var(--radius-full);
  background-color: var(--color-primary);
  transform: scaleX(0);
  transform-origin: center;
  transition: transform var(--transition-normal);
}

.dt-header__nav-link:hover,
.dt-header__nav-link:focus-visible {
  color: var(--gray-900);
}

.dt-header__nav-link:hover::after,
.dt-header__nav-link:focus-visible::after {
  transform: scaleX(1);
}

.dt-header__actions {
  display: inline-flex;
  align-items: center;
  gap: var(--space-6);
  margin-left: var(--space-8);
}

.dt-header__icon-link {
  position: relative;
  display: inline-flex;
  align-items: center;
  justify-content: center;
  width: 36px;
  height: 36px;
  border-radius: var(--radius-full);
  border: 1px solid var(--color-border-subtle);
  background-color: var(--color-surface-muted);
  color: var(--gray-700);
  font-size: 0.9rem;
  transition: background-color var(--transition-normal),
    color var(--transition-normal),
    border-color var(--transition-normal),
    box-shadow var(--transition-fast),
    transform var(--transition-fast);
}

.dt-header__icon-link:hover,
.dt-header__icon-link:focus-visible {
  background-color: var(--color-primary-soft);
  border-color: var(--color-primary);
  color: var(--color-primary-strong);
  box-shadow: var(--shadow-soft);
  transform: translateY(-1px);
}

.dt-header__cta {
  white-space: nowrap;
}

/* Mobile menu toggle */

.dt-header__menu-toggle {
  display: none;
  align-items: center;
  gap: var(--space-4);
  padding: 0.35rem 0.55rem;
  border-radius: var(--radius-md);
  border: 1px solid var(--color-border-subtle);
  background-color: var(--color-surface);
  color: var(--gray-800);
  font-size: var(--font-size-sm);
}

.dt-header__menu-toggle-box {
  width: 22px;
  height: 18px;
  position: relative;
  display: inline-flex;
  align-items: center;
  justify-content: center;
}

.dt-header__menu-toggle-bar {
  position: absolute;
  width: 100%;
  height: 2px;
  border-radius: var(--radius-full);
  background-color: var(--gray-800);
  transition: transform var(--transition-normal),
    opacity var(--transition-fast),
    top var(--transition-normal),
    bottom var(--transition-normal);
}

.dt-header__menu-toggle-bar--top {
  top: 2px;
}

.dt-header__menu-toggle-bar--middle {
  top: 8px;
}

.dt-header__menu-toggle-bar--bottom {
  bottom: 2px;
}

.dt-header__menu-toggle-text {
  font-size: var(--font-size-xs);
}

.dt-header__menu-toggle:focus-visible {
  outline: 2px solid var(--color-primary);
  outline-offset: 2px;
}

/* Mobile state: open */

.dt-header--menu-open .dt-header__menu-toggle-bar--top {
  top: 8px;
  transform: rotate(45deg);
}

.dt-header--menu-open .dt-header__menu-toggle-bar--middle {
  opacity: 0;
}

.dt-header--menu-open .dt-header__menu-toggle-bar--bottom {
  bottom: 8px;
  transform: rotate(-45deg);
}

/* Responsive layout */

@media (max-width: 900px) {
  .dt-header__inner {
    padding-top: var(--space-6);
    padding-bottom: var(--space-6);
  }

  .dt-header__menu-toggle {
    display: inline-flex;
  }

  .dt-header__nav {
    position: absolute;
    left: 0;
    right: 0;
    top: 100%;
    background-color: var(--color-surface);
    border-bottom: 1px solid var(--color-border-subtle);
    box-shadow: var(--shadow-soft);
    transform-origin: top;
    transform: scaleY(0);
    opacity: 0;
    visibility: hidden;
    transition: transform var(--transition-normal),
      opacity var(--transition-normal),
      visibility 0s linear var(--transition-normal);
  }

  .dt-header__nav-list {
    flex-direction: column;
    align-items: flex-start;
    padding: var(--space-8) var(--space-16) var(--space-10);
    gap: var(--space-4);
  }

  .dt-header--menu-open .dt-header__nav {
    transform: scaleY(1);
    opacity: 1;
    visibility: visible;
    transition: transform var(--transition-normal),
      opacity var(--transition-normal);
  }

  .dt-header__nav-link {
    width: 100%;
    padding-block: 0.45rem;
  }

  .dt-header__nav-link::after {
    display: none;
  }

  .dt-header__actions {
    margin-left: 0;
  }

  .dt-header__cta {
    display: none;
  }
}

@media (max-width: 640px) {
  .dt-header__inner {
    gap: var(--space-4);
  }

  .dt-header__site-tagline {
    display: none;
  }

  .dt-header__icon-link {
    width: 32px;
    height: 32px;
  }
}

/* High contrast focus visibility for header links */

.dt-header a:focus-visible {
  outline: 2px solid var(--color-primary);
  outline-offset: 3px;
}