/* ═══════════════════════════════════════════════════════════════════════════
   PHYSICSFORUM.ORG — FORUM SYSTEM STYLES
   ═══════════════════════════════════════════════════════════════════════════ */

/* ── Forum Page Layout ── */
.forum-page {
  max-width: 1280px;
  margin: 0 auto;
  padding: 0 var(--space-4);
}

.forum-layout {
  display: flex;
  flex-direction: column;
  gap: var(--space-8);
  margin-top: var(--space-6);
}

.forum-main {
  flex: 1;
  min-width: 0;
}

.forum-sidebar {
  width: 100%;
  display: flex;
  flex-direction: column;
  gap: var(--space-6);
}

@media (min-width: 1024px) {
  .forum-layout {
    flex-direction: row;
  }
  .forum-sidebar {
    width: 320px;
    flex-shrink: 0;
  }
}

/* ── Forum Page Header ── */
.forum-header {
  background: linear-gradient(135deg, var(--color-space-navy), var(--color-academic-blue));
  padding: var(--space-10) var(--space-4);
  text-align: center;
  margin: -var(--space-6) calc(-1 * var(--space-4)) 0;
  width: auto;
}

.forum-header h1 {
  color: var(--text-inverse);
  font-size: var(--text-3xl);
  font-weight: 800;
  margin-bottom: var(--space-2);
}

.forum-header p {
  color: var(--color-neutron-grey);
  font-family: var(--font-body);
  font-size: var(--text-lg);
  max-width: 600px;
  margin: 0 auto;
}

.forum-stats-bar {
  display: flex;
  flex-wrap: wrap;
  justify-content: center;
  gap: var(--space-4) var(--space-8);
  margin-top: var(--space-6);
  padding-top: var(--space-5);
  border-top: 1px solid rgba(255,255,255,0.1);
}

.forum-stats-bar .stat-item {
  font-size: var(--text-sm);
  color: var(--color-neutron-grey);
}

.forum-stats-bar .stat-item strong {
  color: var(--text-inverse);
  font-weight: 600;
}

@media (min-width: 1024px) {
  .forum-header {
    border-radius: var(--radius-xl);
    margin: var(--space-4) 0 var(--space-8);
  }
}

/* ── Forum Stats Banner ── */
.stats-banner {
  display: grid;
  grid-template-columns: repeat(2, 1fr);
  gap: var(--space-4);
}

.stats-banner .stat-card {
  background: var(--color-academic-blue);
  border-radius: var(--radius-lg);
  padding: var(--space-5);
  text-align: center;
  color: var(--text-inverse);
  transition: var(--transition-base);
}

.stats-banner .stat-card:hover {
  transform: translateY(-2px);
  box-shadow: var(--shadow-lg);
}

.stats-banner .stat-card .stat-icon {
  font-size: var(--text-2xl);
  margin-bottom: var(--space-2);
}

.stats-banner .stat-card .stat-number {
  font-size: var(--text-2xl);
  font-weight: 800;
  color: var(--color-quantum-gold);
  display: block;
}

.stats-banner .stat-card .stat-label {
  font-size: var(--text-sm);
  color: var(--color-neutron-grey);
  margin-top: var(--space-1);
}

@media (min-width: 640px) {
  .stats-banner {
    grid-template-columns: repeat(4, 1fr);
  }
}

/* ── Category Groups ── */
.category-group {
  margin-bottom: var(--space-6);
}

.category-group-header {
  background: var(--color-slate);
  color: var(--color-quantum-gold);
  padding: var(--space-3) var(--space-5);
  border-radius: var(--radius-md) var(--radius-md) 0 0;
  font-size: var(--text-sm);
  font-weight: 700;
  text-transform: uppercase;
  letter-spacing: 0.08em;
  display: flex;
  align-items: center;
  gap: var(--space-2);
}

.category-group-header .group-icon {
  width: 18px;
  height: 18px;
  flex-shrink: 0;
}

.category-list {
  background: var(--color-photon-white);
  border: 1px solid rgba(148,163,184,0.15);
  border-top: none;
  border-radius: 0 0 var(--radius-lg) var(--radius-lg);
  overflow: hidden;
}

.category-row {
  display: grid;
  grid-template-columns: 48px minmax(0, 1fr) 180px;
  gap: var(--space-4);
  padding: var(--space-4) var(--space-5);
  align-items: center;
  border-bottom: 1px solid rgba(148,163,184,0.08);
  transition: background-color 0.15s ease;
  cursor: pointer;
}

.category-row:last-child {
  border-bottom: none;
}

.category-row:hover {
  background: var(--color-ice-blue);
}

.category-row .cat-icon {
  width: 44px;
  height: 44px;
  border-radius: 10px;
  display: flex;
  align-items: center;
  justify-content: center;
  flex-shrink: 0;
  background: linear-gradient(135deg, rgba(37,99,235,0.12), rgba(124,58,237,0.12));
  color: var(--color-electric);
  font-size: 22px;
  font-weight: 800;
}

.category-row .cat-icon svg {
  width: 28px;
  height: 28px;
}

.category-row .cat-info {
  min-width: 0;
}

.category-row .cat-name {
  font-family: var(--font-display);
  font-weight: 600;
  font-size: var(--text-sm);
  color: var(--color-dark-grey);
  display: block;
}

.category-row .cat-name:hover {
  color: var(--color-electric);
  text-decoration: underline;
}

.category-row .cat-desc {
  font-size: var(--text-xs);
  color: var(--color-neutron-grey);
  margin-top: var(--space-1);
  line-height: 1.4;
}

.category-row .cat-tags {
  display: flex;
  gap: var(--space-1);
  margin-top: var(--space-1);
  flex-wrap: wrap;
}

.category-row .cat-tags .tag {
  font-size: 0.65rem;
  padding: 1px 6px;
}

.category-row .cat-stats {
  text-align: right;
  flex-shrink: 0;
  min-width: 140px;
}

.category-row .cat-stats .stat {
  font-size: var(--text-xs);
  color: var(--color-neutron-grey);
  display: block;
}

.category-row .cat-stats .stat strong {
  color: var(--color-dark-grey);
}

.category-row .cat-last-post {
  font-size: var(--text-xs);
  color: var(--color-neutron-grey);
  margin-top: var(--space-1);
  max-width: 160px;
}

.category-row .cat-last-post a {
  color: var(--color-electric);
  font-weight: 500;
  display: block;
  overflow: hidden;
  text-overflow: ellipsis;
  white-space: nowrap;
}

@media (max-width: 639px) {
  .category-row {
    grid-template-columns: 40px minmax(0,1fr);
    gap: var(--space-3);
  }
  .category-row .cat-stats {
    display: none;
  }
}

/* ── Sidebar Widgets ── */
.sidebar-widget {
  background: var(--color-photon-white);
  border: 1px solid rgba(148,163,184,0.15);
  border-radius: var(--radius-lg);
  overflow: hidden;
}

.sidebar-widget-header {
  background: var(--color-academic-blue);
  color: var(--text-inverse);
  padding: var(--space-3) var(--space-5);
  font-size: var(--text-sm);
  font-weight: 700;
  display: flex;
  align-items: center;
  gap: var(--space-2);
}

.sidebar-widget-body {
  padding: var(--space-4);
}

/* Online users widget */
.online-indicator {
  display: inline-flex;
  align-items: center;
  gap: var(--space-2);
  font-size: var(--text-sm);
  color: var(--color-dark-grey);
  font-weight: 500;
}

.online-dot {
  width: 8px;
  height: 8px;
  background: var(--color-fusion-green);
  border-radius: 50%;
  display: inline-block;
  animation: onlinePulse 2s ease-in-out infinite;
}

@keyframes onlinePulse {
  0%, 100% { opacity: 1; }
  50% { opacity: 0.4; }
}

.online-user-row {
  display: flex;
  align-items: center;
  gap: var(--space-3);
  padding: var(--space-2) 0;
}

.online-user-row .avatar {
  width: 32px;
  height: 32px;
}

.online-user-row .user-name {
  font-size: var(--text-sm);
  font-weight: 500;
  color: var(--color-dark-grey);
}

/* Quick Ask widget */
.quick-ask-toggle {
  width: 100%;
  padding: var(--space-3);
  background: var(--color-electric);
  color: var(--text-inverse);
  border: none;
  border-radius: var(--radius-md);
  font-family: var(--font-display);
  font-weight: 600;
  font-size: var(--text-sm);
  cursor: pointer;
  transition: var(--transition-fast);
  display: flex;
  align-items: center;
  justify-content: center;
  gap: var(--space-2);
}

.quick-ask-toggle:hover {
  background: #1d4ed8;
}

.quick-ask-form {
  display: none;
  margin-top: var(--space-3);
}

.quick-ask-form.open {
  display: block;
}

.quick-ask-form textarea {
  width: 100%;
  min-height: 80px;
  padding: var(--space-2) var(--space-3);
  border: 1.5px solid rgba(148,163,184,0.35);
  border-radius: var(--radius-md);
  font-size: var(--text-sm);
  font-family: var(--font-display);
  resize: vertical;
  transition: var(--transition-fast);
}

.quick-ask-form textarea:focus {
  outline: none;
  border-color: var(--color-electric);
  box-shadow: 0 0 0 3px rgba(37,99,235,0.15);
}

.quick-ask-form .qa-actions {
  display: flex;
  gap: var(--space-2);
  margin-top: var(--space-2);
  justify-content: flex-end;
}

/* Tags cloud */
.tags-cloud {
  display: flex;
  flex-wrap: wrap;
  gap: var(--space-2);
}

.tags-cloud .tag-cloud-item {
  font-size: var(--text-xs);
  color: var(--color-electric);
  cursor: pointer;
  padding: 2px 8px;
  border-radius: var(--radius-full);
  background: rgba(37,99,235,0.08);
  transition: var(--transition-fast);
  font-family: var(--font-display);
}

.tags-cloud .tag-cloud-item:hover {
  background: var(--color-electric);
  color: var(--text-inverse);
  text-decoration: none;
}

.tags-cloud .tag-cloud-item.size-xs { font-size: 0.65rem; }
.tags-cloud .tag-cloud-item.size-sm { font-size: 0.75rem; }
.tags-cloud .tag-cloud-item.size-md { font-size: 0.85rem; }
.tags-cloud .tag-cloud-item.size-lg { font-size: 0.95rem; }
.tags-cloud .tag-cloud-item.size-xl { font-size: 1.05rem; }

/* Events widget */
.event-item {
  padding: var(--space-2) 0;
  border-bottom: 1px solid rgba(148,163,184,0.1);
}

.event-item:last-child {
  border-bottom: none;
}

.event-item .event-date {
  font-size: var(--text-xs);
  color: var(--color-quantum-gold);
  font-weight: 600;
}

.event-item .event-title {
  font-size: var(--text-sm);
  font-weight: 500;
  color: var(--color-dark-grey);
  margin-top: 2px;
}

/* ── Category Header ── */
.cat-header {
  background: linear-gradient(135deg, var(--color-academic-blue), var(--color-space-navy));
  border-radius: var(--radius-xl);
  padding: var(--space-8);
  color: var(--text-inverse);
  display: flex;
  flex-direction: column;
  gap: var(--space-4);
}

.cat-header .cat-header-top {
  display: flex;
  align-items: flex-start;
  gap: var(--space-5);
}

.cat-header .cat-header-icon {
  width: 56px;
  height: 56px;
  flex-shrink: 0;
  background: rgba(255,255,255,0.1);
  border-radius: var(--radius-lg);
  display: flex;
  align-items: center;
  justify-content: center;
}

.cat-header .cat-header-icon svg {
  width: 36px;
  height: 36px;
}

.cat-header .cat-header-info h1 {
  font-size: var(--text-2xl);
  margin-bottom: var(--space-1);
}

.cat-header .cat-header-info p {
  color: var(--color-neutron-grey);
  font-family: var(--font-body);
  font-size: var(--text-sm);
}

.cat-header .cat-header-actions {
  display: flex;
  gap: var(--space-3);
  margin-left: auto;
  flex-shrink: 0;
  align-items: flex-start;
}

.cat-header .cat-header-stats {
  display: flex;
  gap: var(--space-6);
  margin-top: var(--space-2);
}

.cat-header .cat-header-stats .stat {
  font-size: var(--text-sm);
  color: var(--color-neutron-grey);
}

.cat-header .cat-header-stats .stat strong {
  color: var(--text-inverse);
}

@media (max-width: 639px) {
  .cat-header .cat-header-actions {
    margin-left: 0;
  }
}

/* ── Filter / Sort Bar ── */
.filter-bar {
  display: flex;
  flex-wrap: wrap;
  gap: var(--space-2);
  padding: var(--space-4) 0;
  border-bottom: 1px solid rgba(148,163,184,0.15);
  align-items: center;
  justify-content: space-between;
}

.filter-tabs {
  display: flex;
  flex-wrap: wrap;
  gap: var(--space-1);
}

.filter-tab {
  padding: var(--space-1) var(--space-3);
  font-size: var(--text-sm);
  font-weight: 500;
  font-family: var(--font-display);
  border-radius: var(--radius-full);
  cursor: pointer;
  transition: var(--transition-fast);
  color: var(--color-dark-grey);
  background: transparent;
  border: none;
  white-space: nowrap;
}

.filter-tab:hover {
  background: var(--color-ice-blue);
  color: var(--color-electric);
}

.filter-tab.active {
  background: var(--color-electric);
  color: var(--text-inverse);
}

.filter-sort {
  display: flex;
  align-items: center;
  gap: var(--space-2);
  font-size: var(--text-sm);
  color: var(--color-neutron-grey);
}

.filter-sort select {
  padding: var(--space-1) var(--space-3);
  border: 1.5px solid rgba(148,163,184,0.35);
  border-radius: var(--radius-md);
  font-size: var(--text-sm);
  font-family: var(--font-display);
  color: var(--color-dark-grey);
  background: var(--color-photon-white);
  cursor: pointer;
}

/* ── Thread List ── */
.thread-list {
  background: var(--color-photon-white);
}

.thread-row {
  display: grid;
  grid-template-columns: 52px 1fr auto;
  gap: var(--space-4);
  padding: var(--space-4);
  border-bottom: 1px solid rgba(148,163,184,0.1);
  transition: var(--transition-fast);
  align-items: start;
}

.thread-row:hover {
  background: var(--color-ice-blue);
}

.thread-row .thread-votes {
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: 2px;
}

.thread-row .thread-votes .vote-count {
  font-size: var(--text-sm);
  font-weight: 600;
  color: var(--color-dark-grey);
  text-align: center;
}

.thread-row .thread-votes .vote-label {
  font-size: 0.6rem;
  color: var(--color-neutron-grey);
  text-transform: uppercase;
}

.thread-row .thread-content {
  min-width: 0;
}

.thread-row .thread-title {
  font-size: var(--text-base);
  font-weight: 600;
  color: var(--color-dark-grey);
  display: block;
  margin-bottom: var(--space-2);
  line-height: 1.4;
}

.thread-row .thread-title:hover {
  color: var(--color-electric);
  text-decoration: underline;
}

.thread-row .thread-meta {
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  gap: var(--space-2) var(--space-3);
  font-size: var(--text-xs);
  color: var(--color-neutron-grey);
}

.thread-row .thread-meta .author {
  display: flex;
  align-items: center;
  gap: var(--space-2);
}

.thread-row .thread-meta .author .avatar {
  width: 20px;
  height: 20px;
  font-size: 0.5rem;
}

.thread-row .thread-meta .author-name {
  font-weight: 500;
  color: var(--color-dark-grey);
}

.thread-row .thread-stats {
  display: flex;
  gap: var(--space-4);
  font-size: var(--text-xs);
  color: var(--color-neutron-grey);
  text-align: right;
  flex-shrink: 0;
  align-items: center;
}

.thread-row .thread-stats .ts-item {
  display: flex;
  flex-direction: column;
  align-items: center;
}

.thread-row .thread-stats .ts-item .ts-num {
  font-weight: 600;
  font-size: var(--text-sm);
  color: var(--color-dark-grey);
}

.thread-row .thread-stats .ts-time {
  font-size: var(--text-xs);
  color: var(--color-neutron-grey);
}

/* Thread row states */
.thread-row.thread-solved {
  border-left: 4px solid var(--color-fusion-green);
  background: rgba(16,185,129,0.03);
}

.thread-row.thread-hot {
  border-left: 4px solid var(--color-quantum-gold);
}

.thread-row.thread-pinned {
  background: rgba(148,163,184,0.06);
}

.thread-row.thread-locked {
  opacity: 0.65;
}

.thread-row.thread-unanswered {
  border-left: 4px solid var(--color-alert-red);
  background: rgba(239,68,68,0.02);
}

/* Difficulty badge */
.difficulty-badge {
  display: inline-flex;
  align-items: center;
  padding: 1px 8px;
  border-radius: var(--radius-full);
  font-size: 0.6rem;
  font-weight: 600;
  font-family: var(--font-display);
  text-transform: uppercase;
  letter-spacing: 0.03em;
}

.difficulty-badge.beginner { background: rgba(16,185,129,0.12); color: var(--color-fusion-green); }
.difficulty-badge.intermediate { background: rgba(245,158,11,0.12); color: var(--color-quantum-gold); }
.difficulty-badge.advanced { background: rgba(239,68,68,0.1); color: var(--color-alert-red); }
.difficulty-badge.graduate { background: rgba(124,58,237,0.1); color: var(--color-soft-purple); }

@media (max-width: 639px) {
  .thread-row {
    grid-template-columns: 42px 1fr;
  }
  .thread-row .thread-stats {
    display: none;
  }
}

/* ── Pagination ── */
.pagination-row {
  display: flex;
  justify-content: center;
  gap: var(--space-1);
  padding: var(--space-6) 0;
}

.pagination-row .page-link {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  min-width: 36px;
  height: 36px;
  padding: var(--space-1) var(--space-3);
  border-radius: var(--radius-md);
  font-size: var(--text-sm);
  font-weight: 500;
  font-family: var(--font-display);
  color: var(--color-dark-grey);
  transition: var(--transition-fast);
}

.pagination-row .page-link:hover {
  background: var(--color-ice-blue);
  color: var(--color-electric);
  text-decoration: none;
}

.pagination-row .page-link.active {
  background: var(--color-electric);
  color: var(--text-inverse);
}

.pagination-row .page-link.disabled {
  color: var(--color-neutron-grey);
  pointer-events: none;
}

/* ── Thread Detail Page ── */
.thread-header {
  padding: var(--space-6) 0;
  border-bottom: 1px solid rgba(148,163,184,0.15);
  margin-bottom: var(--space-6);
}

.thread-header h1 {
  font-size: var(--text-2xl);
  margin: var(--space-3) 0;
  line-height: 1.3;
}

.thread-tags {
  display: flex;
  flex-wrap: wrap;
  gap: var(--space-2);
  margin: var(--space-3) 0;
}

.thread-meta-bar {
  display: flex;
  flex-wrap: wrap;
  gap: var(--space-4);
  font-size: var(--text-sm);
  color: var(--color-neutron-grey);
  align-items: center;
}

.thread-meta-bar .meta-item {
  display: flex;
  align-items: center;
  gap: var(--space-1);
}

.thread-actions {
  display: flex;
  gap: var(--space-2);
  margin-top: var(--space-3);
}

/* Post layout */
.post-container {
  display: flex;
  flex-direction: column;
  gap: var(--space-6);
}

.post-card {
  display: grid;
  grid-template-columns: 1fr;
  background: var(--color-photon-white);
  border: 1px solid rgba(148,163,184,0.15);
  border-radius: var(--radius-lg);
  overflow: hidden;
}

@media (min-width: 640px) {
  .post-card {
    grid-template-columns: 180px 1fr;
  }
}

.post-sidebar {
  background: var(--color-academic-blue);
  padding: var(--space-5);
  color: var(--text-inverse);
  display: flex;
  flex-direction: column;
  align-items: center;
  text-align: center;
  gap: var(--space-3);
}

@media (max-width: 639px) {
  .post-sidebar {
    flex-direction: row;
    flex-wrap: wrap;
    justify-content: center;
    padding: var(--space-3) var(--space-4);
    gap: var(--space-3);
  }
}

.post-sidebar .author-avatar {
  width: 80px;
  height: 80px;
  border-radius: 50%;
  background: rgba(255,255,255,0.15);
  display: flex;
  align-items: center;
  justify-content: center;
  font-size: var(--text-2xl);
  font-weight: 800;
  color: var(--color-quantum-gold);
}

@media (max-width: 639px) {
  .post-sidebar .author-avatar {
    width: 40px;
    height: 40px;
    font-size: var(--text-base);
  }
}

.post-sidebar .author-name {
  font-weight: 700;
  font-size: var(--text-sm);
}

.post-sidebar .author-tier {
  font-size: var(--text-xs);
  padding: 1px 10px;
  border-radius: var(--radius-full);
  background: rgba(255,255,255,0.12);
}

.post-sidebar .author-stats {
  font-size: var(--text-xs);
  color: rgba(255,255,255,0.6);
  display: flex;
  flex-direction: column;
  gap: var(--space-1);
}

.post-sidebar .author-stats span {
  white-space: nowrap;
}

@media (max-width: 639px) {
  .post-sidebar .author-stats {
    flex-direction: row;
    gap: var(--space-3);
  }
}

.post-content {
  padding: var(--space-6);
  display: flex;
  flex-direction: column;
}

.post-content .post-body {
  font-family: var(--font-body);
  font-size: var(--text-lg);
  line-height: 1.75;
  color: var(--color-dark-grey);
  flex: 1;
}

.post-content .post-body p {
  max-width: none;
}

.post-content .post-footer {
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  justify-content: space-between;
  gap: var(--space-3);
  margin-top: var(--space-5);
  padding-top: var(--space-4);
  border-top: 1px solid rgba(148,163,184,0.1);
  font-size: var(--text-xs);
  color: var(--color-neutron-grey);
}

.post-content .post-footer .post-edited {
  font-style: italic;
}

/* Reaction bar */
.reaction-bar {
  display: flex;
  flex-wrap: wrap;
  gap: var(--space-2);
  margin-top: var(--space-3);
}

.reaction-btn {
  display: inline-flex;
  align-items: center;
  gap: 4px;
  padding: var(--space-1) var(--space-3);
  border-radius: var(--radius-full);
  font-size: var(--text-xs);
  font-weight: 500;
  color: var(--color-dark-grey);
  background: rgba(148,163,184,0.08);
  cursor: pointer;
  transition: var(--transition-fast);
  border: none;
  font-family: var(--font-display);
}

.reaction-btn:hover {
  background: var(--color-ice-blue);
  color: var(--color-electric);
}

.reaction-btn.reacted {
  background: var(--color-ice-blue);
  color: var(--color-electric);
  font-weight: 600;
}

/* Post state variations */
.post-card.best-answer {
  border: 2px solid var(--color-fusion-green);
}

.post-card.best-answer::before {
  content: '✓ Best Answer';
  display: block;
  background: var(--color-fusion-green);
  color: var(--text-inverse);
  font-size: var(--text-xs);
  font-weight: 700;
  padding: var(--space-2) var(--space-5);
  text-align: center;
  letter-spacing: 0.04em;
  grid-column: 1 / -1;
}

.post-card.moderator-reply {
  border: 2px solid var(--color-quantum-gold);
}

.post-card.moderator-reply .author-name::after {
  content: ' [MOD]';
  color: var(--color-quantum-gold);
  font-size: var(--text-xs);
}

/* Jump to best answer */
.jump-link {
  display: flex;
  align-items: center;
  justify-content: center;
  gap: var(--space-2);
  padding: var(--space-4);
  background: rgba(16,185,129,0.08);
  border-radius: var(--radius-md);
  font-size: var(--text-sm);
  font-weight: 600;
  color: var(--color-fusion-green);
  cursor: pointer;
  transition: var(--transition-fast);
}

.jump-link:hover {
  background: rgba(16,185,129,0.15);
  text-decoration: none;
}

.jump-link svg {
  animation: bounceDown 1.5s infinite;
}

@keyframes bounceDown {
  0%, 100% { transform: translateY(0); }
  50% { transform: translateY(4px); }
}

/* ── Reply Composer ── */
.reply-composer {
  background: var(--color-photon-white);
  border: 1px solid rgba(148,163,184,0.15);
  border-radius: var(--radius-lg);
  margin-top: var(--space-8);
  overflow: hidden;
}

.reply-composer-header {
  background: var(--color-academic-blue);
  color: var(--text-inverse);
  padding: var(--space-3) var(--space-5);
  font-weight: 700;
  font-size: var(--text-sm);
}

.composer-toolbar {
  display: flex;
  flex-wrap: wrap;
  gap: 2px;
  padding: var(--space-2) var(--space-4);
  background: var(--color-photon-white);
  border-bottom: 1px solid rgba(148,163,184,0.1);
}

.toolbar-btn {
  width: 34px;
  height: 34px;
  display: inline-flex;
  align-items: center;
  justify-content: center;
  border-radius: var(--radius-md);
  font-size: var(--text-sm);
  color: var(--color-dark-grey);
  cursor: pointer;
  transition: var(--transition-fast);
  border: none;
  background: transparent;
  font-family: var(--font-display);
  font-weight: 600;
}

.toolbar-btn:hover {
  background: var(--color-ice-blue);
  color: var(--color-electric);
}

.toolbar-btn:active {
  background: var(--color-electric);
  color: var(--text-inverse);
}

.toolbar-separator {
  width: 1px;
  background: rgba(148,163,184,0.2);
  margin: 2px var(--space-1);
}

.composer-body {
  padding: var(--space-4);
}

.composer-body textarea {
  width: 100%;
  min-height: 160px;
  padding: var(--space-4);
  border: 1.5px solid rgba(148,163,184,0.2);
  border-radius: var(--radius-md);
  font-family: var(--font-display);
  font-size: var(--text-sm);
  line-height: 1.6;
  resize: vertical;
  transition: var(--transition-fast);
}

.composer-body textarea:focus {
  outline: none;
  border-color: var(--color-electric);
  box-shadow: 0 0 0 3px rgba(37,99,235,0.1);
}

.composer-footer {
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  justify-content: space-between;
  gap: var(--space-4);
  padding: var(--space-3) var(--space-5);
  background: rgba(148,163,184,0.03);
  border-top: 1px solid rgba(148,163,184,0.1);
}

.composer-footer .char-count {
  font-size: var(--text-xs);
  color: var(--color-neutron-grey);
}

.composer-footer .char-count.warning {
  color: var(--color-alert-red);
  font-weight: 600;
}

.composer-footer .composer-actions {
  display: flex;
  gap: var(--space-2);
}

.composer-footer .latex-toggle {
  display: flex;
  align-items: center;
  gap: var(--space-2);
  font-size: var(--text-xs);
  color: var(--color-dark-grey);
  cursor: pointer;
}

.latex-preview-pane {
  margin-top: var(--space-3);
  padding: var(--space-4);
  background: var(--color-ice-blue);
  border-radius: var(--radius-md);
  min-height: 60px;
  font-size: var(--text-lg);
  display: none;
}

.latex-preview-pane.show {
  display: block;
}

/* ── Equation Editor Modal ── */
.equation-editor {
  background: var(--color-photon-white);
  border-radius: var(--radius-xl);
  box-shadow: var(--shadow-xl);
  width: 90%;
  max-width: 900px;
  max-height: 85vh;
  display: flex;
  flex-direction: column;
}

.equation-editor-header {
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding: var(--space-4) var(--space-6);
  border-bottom: 1px solid rgba(148,163,184,0.15);
}

.equation-editor-header h3 {
  font-size: var(--text-lg);
}

.equation-editor-close {
  width: 36px;
  height: 36px;
  display: flex;
  align-items: center;
  justify-content: center;
  background: none;
  border: none;
  border-radius: var(--radius-full);
  font-size: var(--text-lg);
  cursor: pointer;
  color: var(--color-neutron-grey);
  transition: var(--transition-fast);
}

.equation-editor-close:hover {
  background: rgba(148,163,184,0.1);
  color: var(--color-dark-grey);
}

.equation-editor-body {
  display: flex;
  flex: 1;
  min-height: 0;
  overflow: hidden;
}

@media (max-width: 639px) {
  .equation-editor-body {
    flex-direction: column;
  }
}

.equation-editor-input {
  flex: 1;
  padding: var(--space-4);
  display: flex;
  flex-direction: column;
}

.equation-editor-input textarea {
  flex: 1;
  width: 100%;
  min-height: 200px;
  padding: var(--space-4);
  border: 1.5px solid rgba(148,163,184,0.35);
  border-radius: var(--radius-md);
  font-family: var(--font-mono);
  font-size: var(--text-sm);
  line-height: 1.6;
  resize: none;
  color: var(--color-code-bg);
  background: var(--color-photon-white);
}

.equation-editor-input textarea:focus {
  outline: none;
  border-color: var(--color-electric);
  box-shadow: 0 0 0 3px rgba(37,99,235,0.1);
}

.equation-editor-preview {
  flex: 1;
  padding: var(--space-4);
  background: var(--color-ice-blue);
  display: flex;
  align-items: center;
  justify-content: center;
  font-size: var(--text-xl);
  min-height: 200px;
}

.equation-error {
  padding: var(--space-2) var(--space-4);
  background: rgba(239,68,68,0.08);
  color: var(--color-alert-red);
  font-size: var(--text-xs);
  font-family: var(--font-mono);
  border-radius: var(--radius-sm);
  margin-top: var(--space-2);
  display: none;
}

.equation-error.show {
  display: block;
}

/* Symbol palette */
.symbol-palette {
  border-top: 1px solid rgba(148,163,184,0.15);
  padding: var(--space-3) var(--space-4);
}

.symbol-palette-tabs {
  display: flex;
  gap: var(--space-1);
  margin-bottom: var(--space-3);
  flex-wrap: wrap;
}

.symbol-tab {
  padding: var(--space-1) var(--space-3);
  font-size: var(--text-xs);
  font-weight: 500;
  font-family: var(--font-display);
  border-radius: var(--radius-full);
  cursor: pointer;
  color: var(--color-dark-grey);
  background: transparent;
  border: none;
  transition: var(--transition-fast);
}

.symbol-tab:hover { background: var(--color-ice-blue); }
.symbol-tab.active { background: var(--color-electric); color: var(--text-inverse); }

.symbol-grid {
  display: flex;
  flex-wrap: wrap;
  gap: 4px;
  max-height: 120px;
  overflow-y: auto;
}

.symbol-btn {
  min-width: 36px;
  height: 34px;
  display: inline-flex;
  align-items: center;
  justify-content: center;
  border-radius: var(--radius-sm);
  font-size: var(--text-sm);
  font-family: var(--font-mono);
  color: var(--color-dark-grey);
  cursor: pointer;
  transition: var(--transition-fast);
  background: none;
  border: 1px solid rgba(148,163,184,0.15);
}

.symbol-btn:hover {
  background: var(--color-electric);
  color: var(--text-inverse);
  border-color: var(--color-electric);
}

.equation-editor-footer {
  display: flex;
  gap: var(--space-3);
  padding: var(--space-4) var(--space-6);
  border-top: 1px solid rgba(148,163,184,0.15);
  justify-content: flex-end;
}

/* ── New Thread Page ── */
.new-thread-layout {
  display: flex;
  flex-direction: column;
  gap: var(--space-6);
}

.new-thread-main {
  flex: 1;
}

.new-thread-sidebar {
  width: 100%;
  display: flex;
  flex-direction: column;
  gap: var(--space-6);
}

@media (min-width: 1024px) {
  .new-thread-layout {
    flex-direction: row;
  }
  .new-thread-sidebar {
    width: 340px;
    flex-shrink: 0;
  }
}

.new-thread-form {
  background: var(--color-photon-white);
  border: 1px solid rgba(148,163,184,0.15);
  border-radius: var(--radius-lg);
  overflow: hidden;
}

.new-thread-form-header {
  background: var(--color-academic-blue);
  color: var(--text-inverse);
  padding: var(--space-4) var(--space-6);
  font-weight: 700;
  font-size: var(--text-lg);
}

.new-thread-form-body {
  padding: var(--space-6);
  display: flex;
  flex-direction: column;
  gap: var(--space-5);
}

/* Tag input */
.tag-input-wrapper {
  display: flex;
  flex-wrap: wrap;
  gap: var(--space-2);
  padding: var(--space-2) var(--space-3);
  border: 1.5px solid rgba(148,163,184,0.35);
  border-radius: var(--radius-md);
  min-height: 44px;
  align-items: center;
  cursor: text;
  transition: var(--transition-fast);
  background: var(--color-photon-white);
}

.tag-input-wrapper:focus-within {
  border-color: var(--color-electric);
  box-shadow: 0 0 0 3px rgba(37,99,235,0.1);
}

.tag-input-wrapper .tag-chip {
  display: inline-flex;
  align-items: center;
  gap: 4px;
  padding: 2px 10px;
  background: var(--color-ice-blue);
  color: var(--color-electric);
  border-radius: var(--radius-full);
  font-size: var(--text-xs);
  font-weight: 500;
  white-space: nowrap;
}

.tag-input-wrapper .tag-chip .tag-remove {
  cursor: pointer;
  width: 16px;
  height: 16px;
  display: inline-flex;
  align-items: center;
  justify-content: center;
  border-radius: 50%;
  font-size: 10px;
  border: none;
  background: none;
  color: var(--color-electric);
  transition: var(--transition-fast);
}

.tag-input-wrapper .tag-chip .tag-remove:hover {
  background: var(--color-alert-red);
  color: var(--text-inverse);
}

.tag-input-wrapper input {
  border: none;
  outline: none;
  flex: 1;
  min-width: 100px;
  font-size: var(--text-sm);
  font-family: var(--font-display);
  color: var(--color-dark-grey);
  padding: var(--space-1) 0;
}

/* Difficulty selector row */
.difficulty-selector {
  display: flex;
  gap: var(--space-2);
  flex-wrap: wrap;
}

.diff-option {
  padding: var(--space-2) var(--space-4);
  border-radius: var(--radius-full);
  font-size: var(--text-sm);
  font-weight: 500;
  font-family: var(--font-display);
  cursor: pointer;
  transition: var(--transition-fast);
  border: 1.5px solid rgba(148,163,184,0.3);
  background: transparent;
  color: var(--color-dark-grey);
}

.diff-option:hover {
  border-color: var(--color-electric);
  color: var(--color-electric);
}

.diff-option.selected.beginner {
  background: rgba(16,185,129,0.12);
  border-color: var(--color-fusion-green);
  color: var(--color-fusion-green);
  font-weight: 600;
}

.diff-option.selected.intermediate {
  background: rgba(245,158,11,0.12);
  border-color: var(--color-quantum-gold);
  color: var(--color-quantum-gold);
  font-weight: 600;
}

.diff-option.selected.advanced {
  background: rgba(239,68,68,0.1);
  border-color: var(--color-alert-red);
  color: var(--color-alert-red);
  font-weight: 600;
}

.diff-option.selected.graduate {
  background: rgba(124,58,237,0.1);
  border-color: var(--color-soft-purple);
  color: var(--color-soft-purple);
  font-weight: 600;
}

/* Title input character count */
.title-input-group {
  position: relative;
}

.title-input-group .title-char-count {
  position: absolute;
  right: var(--space-4);
  top: 50%;
  transform: translateY(-50%);
  font-size: var(--text-xs);
  color: var(--color-neutron-grey);
  font-family: var(--font-display);
}

.title-input-group .title-char-count.warning {
  color: var(--color-alert-red);
}

/* Tips card */
.tips-card {
  background: var(--color-photon-white);
  border: 1px solid rgba(148,163,184,0.15);
  border-radius: var(--radius-lg);
  overflow: hidden;
}

.tips-card-header {
  background: var(--color-academic-blue);
  color: var(--text-inverse);
  padding: var(--space-3) var(--space-5);
  font-weight: 700;
  font-size: var(--text-sm);
  display: flex;
  align-items: center;
  gap: var(--space-2);
}

.tips-card-body {
  padding: var(--space-4);
}

.tips-card-body .tip-item {
  display: flex;
  gap: var(--space-2);
  font-size: var(--text-sm);
  color: var(--color-dark-grey);
  padding: var(--space-2) 0;
  align-items: flex-start;
}

.tips-card-body .tip-item .tip-check {
  color: var(--color-fusion-green);
  flex-shrink: 0;
  font-weight: 700;
}

/* Similar threads */
.similar-threads-card {
  background: var(--color-photon-white);
  border: 1px solid rgba(148,163,184,0.15);
  border-radius: var(--radius-lg);
  overflow: hidden;
}

.similar-threads-card-header {
  background: var(--color-slate);
  color: var(--text-inverse);
  padding: var(--space-3) var(--space-5);
  font-weight: 700;
  font-size: var(--text-sm);
}

.similar-threads-card-body {
  padding: var(--space-4);
}

.similar-thread-item {
  padding: var(--space-3) 0;
  border-bottom: 1px solid rgba(148,163,184,0.1);
  cursor: pointer;
  transition: var(--transition-fast);
}

.similar-thread-item:last-child {
  border-bottom: none;
}

.similar-thread-item:hover {
  color: var(--color-electric);
}

.similar-thread-item .st-title {
  font-size: var(--text-sm);
  font-weight: 500;
  line-height: 1.4;
}

.similar-thread-item .st-meta {
  font-size: var(--text-xs);
  color: var(--color-neutron-grey);
  margin-top: var(--space-1);
}

/* Ask sticky button */
.sidebar-ask-btn {
  position: sticky;
  top: var(--space-6);
}

/* Subscribe button */
.btn-subscribe {
  white-space: nowrap;
}

.btn-subscribe.subscribed {
  background: var(--color-fusion-green);
  color: var(--text-inverse);
  border-color: var(--color-fusion-green);
}

/* Top contributors */
.contributor-row {
  display: flex;
  align-items: center;
  gap: var(--space-3);
  padding: var(--space-2) 0;
}

.contributor-row .avatar {
  width: 32px;
  height: 32px;
  flex-shrink: 0;
}

.contributor-row .contributor-name {
  font-size: var(--text-sm);
  font-weight: 500;
  color: var(--color-dark-grey);
}

.contributor-row .contributor-count {
  margin-left: auto;
  font-size: var(--text-xs);
  color: var(--color-neutron-grey);
  font-weight: 500;
}

/* Post of the week */
.potw-card {
  padding: var(--space-3);
  background: rgba(245,158,11,0.06);
  border-radius: var(--radius-md);
  border-left: 3px solid var(--color-quantum-gold);
}

.potw-card .potw-title {
  font-size: var(--text-sm);
  font-weight: 600;
  color: var(--color-dark-grey);
  margin-bottom: var(--space-1);
}

.potw-card .potw-meta {
  font-size: var(--text-xs);
  color: var(--color-neutron-grey);
}

/* ── Utility links for forums ── */
.forum-breadcrumb-wrapper {
  padding: var(--space-3) 0;
}

/* Preview tab in new thread */
.preview-pane {
  padding: var(--space-4);
  border: 1.5px solid rgba(148,163,184,0.2);
  border-radius: var(--radius-md);
  font-family: var(--font-body);
  font-size: var(--text-base);
  line-height: 1.75;
  min-height: 200px;
  background: var(--color-photon-white);
}

/* Responsive adjustments */
@media (max-width: 639px) {
  .filter-bar {
    flex-direction: column;
    align-items: flex-start;
  }
  .post-content {
    padding: var(--space-4);
  }
  .post-content .post-body {
    font-size: var(--text-base);
  }
  .thread-header h1 {
    font-size: var(--text-xl);
  }
}

/* Thread solved icon */
.thread-solved-icon {
  color: var(--color-fusion-green);
  font-weight: 700;
  margin-left: var(--space-2);
}

/* Poll icon */
.poll-icon {
  display: inline-flex;
  align-items: center;
  gap: 3px;
  font-size: var(--text-xs);
}

/* Section heading for forum content */
.forum-section-title {
  font-size: var(--text-xl);
  font-weight: 700;
  color: var(--color-dark-grey);
  margin-bottom: var(--space-4);
  display: flex;
  align-items: center;
  gap: var(--space-3);
}

.forum-section-title::after {
  content: '';
  flex: 1;
  height: 1px;
  background: rgba(148,163,184,0.2);
}

/* Empty states */
.empty-state {
  text-align: center;
  padding: var(--space-12) var(--space-4);
  color: var(--color-neutron-grey);
}

.empty-state .empty-icon {
  font-size: var(--text-4xl);
  margin-bottom: var(--space-4);
}

/* Highlighted search terms in similar threads */
.highlight {
  background: rgba(245,158,11,0.2);
  padding: 0 2px;
  border-radius: 2px;
}

/* Print styles */
@media print {
  .forum-sidebar, .reply-composer, .pf-navbar, .pf-footer,
  .composer-toolbar, .thread-actions {
    display: none !important;
  }
  .post-card {
    break-inside: avoid;
    border: 1px solid #ddd;
  }
}

/* Animations for state transitions */
@keyframes fadeInUp {
  from { opacity: 0; transform: translateY(10px); }
  to { opacity: 1; transform: translateY(0); }
}

.post-card {
  animation: fadeInUp 0.3s ease;
}

/* Sticky reply button on mobile */
.mobile-reply-fab {
  position: fixed;
  bottom: var(--space-6);
  right: var(--space-6);
  width: 56px;
  height: 56px;
  border-radius: 50%;
  background: var(--color-electric);
  color: var(--text-inverse);
  border: none;
  box-shadow: var(--shadow-xl);
  display: flex;
  align-items: center;
  justify-content: center;
  font-size: var(--text-xl);
  cursor: pointer;
  z-index: var(--z-sticky);
  transition: var(--transition-base);
}

.mobile-reply-fab:hover {
  transform: scale(1.1);
  box-shadow: var(--shadow-glow);
}

@media (min-width: 1024px) {
  .mobile-reply-fab {
    display: none;
  }
}

/* ── v5.2: per-user avatar tint ────────────────────────────────────────────
   Previously every commenter's avatar was the same translucent white circle
   with gold initials, so a thread of eight replies looked like one person
   talking to themselves. The gradient now comes from an inline style keyed
   to the user (see pf_avatar_style()), and this rule just makes sure the
   text on top stays readable against any palette entry. */
.author-avatar.author-avatar-tinted {
  color: #fff;
  text-shadow: 0 1px 2px rgba(0,0,0,.35);
  border: 2px solid rgba(255,255,255,.22);
}
[data-theme="dark"] .author-avatar.author-avatar-tinted {
  border-color: rgba(255,255,255,.14);
}