/* ============ HEADER ============ */
.site-header {
  background: rgba(255, 255, 255, 0.82);
  backdrop-filter: blur(24px) saturate(180%);
  -webkit-backdrop-filter: blur(24px) saturate(180%);
  color: var(--c-text);
  position: sticky;
  top: 0;
  z-index: 50;
  border-bottom: 1px solid rgba(15, 23, 42, 0.07);
  box-shadow: 0 1px 0 rgba(15,23,42,.05), 0 4px 24px rgba(15,23,42,.06);
}
.site-header__inner {
  max-width: 1200px;
  margin: 0 auto;
  padding: var(--sp-3) var(--sp-6);
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: var(--sp-4);
}
.site-logo {
  display: flex;
  align-items: center;
  gap: var(--sp-3);
  font-weight: 800;
  font-size: var(--fs-lg);
  letter-spacing: -.02em;
  color: var(--c-text);
  user-select: none;
}
.site-logo__icon {
  width: 40px; height: 40px;
  background: var(--grad-text);
  border-radius: var(--r-md);
  display: flex;
  align-items: center;
  justify-content: center;
  font-size: 1.3rem;
  flex-shrink: 0;
  box-shadow: 0 2px 12px rgba(37,99,235,.35);
}
.site-logo__name {
  background: var(--grad-text);
  -webkit-background-clip: text;
  background-clip: text;
  -webkit-text-fill-color: transparent;
}
.site-logo__sub {
  font-size: var(--fs-xs);
  font-weight: 500;
  color: var(--c-text-3);
  -webkit-text-fill-color: var(--c-text-3);
  margin-top: 1px;
  letter-spacing: 0;
}
/* ── Header nav ── */
.header-nav {
  display: flex;
  align-items: center;
  gap: var(--sp-1);
  margin: 0 var(--sp-2);
}
.header-nav__link {
  display: inline-flex;
  align-items: center;
  gap: 5px;
  padding: 6px var(--sp-3);
  border-radius: var(--r-full);
  font-size: var(--fs-sm);
  font-weight: 500;
  color: var(--c-text-2);
  background: transparent;
  border: none;
  cursor: pointer;
  transition: all var(--t-fast);
  white-space: nowrap;
  letter-spacing: -.005em;
}
.header-nav__link:hover {
  color: var(--c-primary);
  background: var(--c-primary-pale);
}
.header-nav__link.active {
  color: var(--c-primary);
  font-weight: 600;
}
/* Hide nav on small screens */
.header-nav.hidden { display: none; }
@media (max-width: 640px) { .header-nav { display: none; } }

/* My Progress — highlighted pill in header-actions */
.header-nav__link--progress {
  background: var(--grad-card);
  color: #fff !important;
  font-weight: 600;
  padding: 7px var(--sp-4);
  box-shadow: 0 2px 10px rgba(37,99,235,.28);
  letter-spacing: 0;
}
.header-nav__link--progress svg { stroke: #fff; }
.header-nav__link--progress:hover {
  background: var(--grad-card);
  color: #fff !important;
  transform: translateY(-1px);
  box-shadow: 0 5px 18px rgba(37,99,235,.38);
}
@media (max-width: 640px) { .header-nav__link--progress { display: none; } }

.header-actions {
  display: flex;
  align-items: center;
  gap: var(--sp-2);
}
.header-btn {
  display: flex;
  align-items: center;
  justify-content: center;
  width: 38px; height: 38px;
  border-radius: var(--r-md);
  background: transparent;
  color: var(--c-text-2);
  font-size: 1.05rem;
  transition: all var(--t-fast);
  border: 1px solid transparent;
  cursor: pointer;
}
.header-btn:hover {
  background: var(--c-primary-pale);
  color: var(--c-primary);
  border-color: rgba(37,99,235,.15);
}
/* Settings button with label text */
.header-btn--label {
  width: auto;
  padding: 0 var(--sp-3);
  gap: var(--sp-2);
}
.header-btn__label {
  font-size: var(--fs-xs);
  font-weight: 600;
  letter-spacing: .01em;
}
/* Hide label on small screens */
@media (max-width: 640px) { .header-btn__label { display: none; } }

/* ============ CONTAINER ============ */
.container {
  max-width: 1200px;
  margin: 0 auto;
  padding: var(--sp-6) var(--sp-4);
}

/* ============ TOPIC TAB NAV ============ */
.topic-tabs-wrapper {
  background: rgba(255,255,255,0.9);
  backdrop-filter: blur(16px);
  -webkit-backdrop-filter: blur(16px);
  border-bottom: 1px solid var(--c-border);
  position: sticky;
  top: 65px;
  z-index: 40;
  box-shadow: var(--shadow-xs);
}
.topic-tabs {
  max-width: 1200px;
  margin: 0 auto;
  padding: 0 var(--sp-4);
  display: flex;
  overflow-x: auto;
  scrollbar-width: none;
}
.topic-tabs::-webkit-scrollbar { display: none; }
.topic-tab {
  flex-shrink: 0;
  padding: var(--sp-4) var(--sp-5);
  font-size: var(--fs-sm);
  font-weight: 600;
  color: var(--c-text-3);
  border-bottom: 2px solid transparent;
  cursor: pointer;
  transition: all var(--t-fast);
  white-space: nowrap;
  display: flex;
  align-items: center;
  gap: var(--sp-2);
  letter-spacing: .01em;
}
.topic-tab:hover {
  color: var(--c-primary);
  background: var(--c-primary-pale);
}
.topic-tab.active {
  color: var(--c-primary);
  border-bottom-color: var(--c-primary);
}

/* ============ SECTION TITLE ============ */
.section-title {
  font-size: var(--fs-xl);
  font-weight: 800;
  color: var(--c-text);
  margin-bottom: var(--sp-6);
  display: flex;
  align-items: center;
  gap: var(--sp-3);
  letter-spacing: -.02em;
}
.section-title::after {
  content: '';
  flex: 1;
  height: 1px;
  background: var(--c-border);
  border-radius: var(--r-full);
}

/* ============ FOOTER ============ */
.site-footer {
  text-align: center;
  padding: var(--sp-8) var(--sp-4) var(--sp-6);
  color: var(--c-text-3);
  font-size: var(--fs-xs);
  border-top: 1px solid var(--c-border-light);
  margin-top: var(--sp-10);
}