/* ============================================================
   style.css — Karpathy-style Minimal Academic Homepage
   나사렛대학교 Database and Information System
   ============================================================ */

@import url('variables.css');

/* ============================================================
   1. Reset & Base
   ============================================================ */

*, *::before, *::after {
  box-sizing: border-box;
  margin: 0;
  padding: 0;
}

html {
  font-size: 16px;
  scroll-behavior: smooth;
  scroll-padding-top: 56px;
}

body {
  font-family: var(--font-body);
  font-size: 0.9375rem;
  line-height: 1.8;
  color: var(--color-text);
  background-color: var(--color-bg);
  -webkit-font-smoothing: antialiased;
}

h1, h2, h3, h4, h5, h6 {
  font-family: var(--font-heading);
  line-height: 1.35;
  color: var(--color-text);
  font-weight: 700;
}

a {
  color: var(--color-link);
  text-decoration: none;
}

a:hover {
  text-decoration: underline;
  color: var(--color-link-hover);
}

img {
  max-width: 100%;
  height: auto;
  display: block;
}

ul, ol { list-style: none; }

button {
  font-family: var(--font-body);
  cursor: pointer;
  border: none;
  background: none;
}

/* ============================================================
   2. Skip Link
   ============================================================ */

.skip-link {
  position: absolute;
  top: -100%;
  left: var(--sp-md);
  z-index: 9999;
  padding: var(--sp-xs) var(--sp-md);
  background: var(--color-text);
  color: #fff;
  font-size: 0.8125rem;
  transition: top 0.2s;
}

.skip-link:focus {
  top: 0;
  text-decoration: none;
}

/* ============================================================
   3. Container
   ============================================================ */

.container {
  width: 100%;
  max-width: var(--container-max);
  margin-inline: auto;
  padding-inline: var(--sp-lg);
}

/* ============================================================
   4. Header — Clean top bar
   ============================================================ */

.site-header {
  border-bottom: 1px solid var(--color-border);
  background: var(--color-bg);
}

.header-inner {
  display: flex;
  align-items: center;
  justify-content: center;
  gap: var(--sp-md);
  padding-block: var(--sp-md);
}

.site-branding {
  min-width: 0;
}

.site-title-link {
  color: var(--color-text);
  text-decoration: none;
}

.site-title-link:hover {
  text-decoration: none;
  color: var(--color-text);
}

.site-title {
  display: block;
  font-family: var(--font-heading);
  font-size: 0.9375rem;
  font-weight: 700;
  color: var(--color-text);
  letter-spacing: -0.01em;
}

.professor-name {
  display: block;
  font-size: 0.8125rem;
  color: var(--color-text-muted);
  font-weight: 400;
  margin-top: 1px;
}

/* Navigation */
.site-nav {
  flex-shrink: 0;
}

.nav-list {
  display: flex;
  align-items: center;
  gap: 0;
}

.nav-link {
  display: block;
  padding: var(--sp-xs) var(--sp-md);
  color: var(--color-text-muted);
  font-size: 1rem;
  font-weight: 500;
  transition: color 0.15s;
}

.nav-link:hover,
.nav-link.active {
  color: var(--color-text);
  text-decoration: none;
}

/* Hamburger */
.hamburger {
  display: none;
  flex-direction: column;
  justify-content: center;
  gap: 4px;
  width: 32px;
  height: 32px;
  padding: 4px;
  flex-shrink: 0;
}

.hamburger-bar {
  display: block;
  width: 100%;
  height: 2px;
  background: var(--color-text);
  border-radius: 1px;
}

/* ============================================================
   5. Hero Banner
   ============================================================ */

.hero-banner {
  position: relative;
  width: 100%;
  height: 320px;
  overflow: hidden;
  background: #000;
}

.hero-banner-img {
  width: 100%;
  height: 100%;
  object-fit: cover;
  object-position: center center;
  display: block;
}

.hero-overlay {
  position: absolute;
  inset: 0;
  display: flex;
  align-items: center;
  justify-content: center;
  background: linear-gradient(
    to bottom,
    rgba(0, 0, 0, 0.2) 0%,
    rgba(0, 0, 0, 0.65) 100%
  );
}

.hero-title {
  font-family: var(--font-heading);
  font-size: 2.48rem;
  font-weight: 700;
  color: #ffffff;
  text-align: center;
  text-shadow: 0 2px 12px rgba(0, 0, 0, 0.6);
  letter-spacing: -0.01em;
  line-height: 1.3;
}

.hero-subtitle {
  font-size: 1.4rem;
  font-weight: 400;
  color: rgba(255, 255, 255, 0.85);
  text-align: center;
  text-shadow: 0 1px 8px rgba(0, 0, 0, 0.5);
  margin-top: var(--sp-xs);
}

.hero-tagline {
  font-family: 'Georgia', 'Times New Roman', serif;
  font-style: italic;
  font-size: 1.16rem;
  font-weight: 400;
  color: #ffffff;
  text-align: center;
  text-shadow: 0 2px 12px rgba(0, 0, 0, 0.7);
  margin-top: var(--sp-lg);
  line-height: 2.2;
  letter-spacing: 0.04em;
  max-width: 720px;
  margin-inline: auto;
}

.hero-tagline em {
  font-style: italic;
  color: #ffffff;
}

/* ============================================================
   6. Sections — Clean, generous spacing
   ============================================================ */

section {
  padding-block: var(--sp-2xl);
}

section + section {
  border-top: 1px solid var(--color-border);
}

.section-heading {
  font-family: var(--font-heading);
  font-size: 1.375rem;
  font-weight: 700;
  color: var(--color-text);
  margin-bottom: var(--sp-xl);
  letter-spacing: -0.01em;
}

/* ============================================================
   6. Card — Minimal
   ============================================================ */

.card {
  padding: var(--sp-lg);
  border: 1px solid var(--color-border);
  border-radius: 4px;
  background: var(--color-bg);
}

.card-header {
  display: flex;
  align-items: flex-start;
  justify-content: space-between;
  gap: var(--sp-sm);
  margin-bottom: var(--sp-sm);
}

.card-title {
  font-size: 1rem;
  font-weight: 700;
  line-height: 1.4;
}

/* ============================================================
   7. Badge
   ============================================================ */

.badge {
  display: inline-block;
  padding: 1px 8px;
  font-size: 0.6875rem;
  font-weight: 600;
  border-radius: 3px;
  text-transform: uppercase;
  letter-spacing: 0.03em;
  white-space: nowrap;
  vertical-align: middle;
}

.badge--ongoing {
  background: #e8f5e9;
  color: #2e7d32;
}

.badge--completed {
  background: #f3f4f6;
  color: var(--color-text-muted);
}

.badge--award {
  background: #fef3c7;
  color: #92400e;
}

.badge--conference {
  background: #d1fae5;
  color: #065f46;
}

.badge--press {
  background: #dbeafe;
  color: #1d4ed8;
}

.badge--notice {
  background: #f3f4f6;
  color: var(--color-text-muted);
}

/* ============================================================
   8. Tag
   ============================================================ */

.tag {
  display: inline-block;
  padding: 2px 10px;
  font-size: 0.75rem;
  font-weight: 500;
  color: var(--color-text-muted);
  background: var(--color-bg-alt);
  border: 1px solid var(--color-border);
  border-radius: 3px;
}

.tag-list {
  display: flex;
  flex-wrap: wrap;
  gap: 6px;
}

/* ============================================================
   9. Buttons / Links
   ============================================================ */

.ext-link {
  display: inline-block;
  font-size: 0.8125rem;
  color: var(--color-link);
  padding: 2px 0;
  margin-right: var(--sp-md);
}

.ext-link::before {
  content: '→ ';
  font-size: 0.75rem;
}

/* Filter bar */
.filter-bar {
  display: flex;
  gap: 0;
  margin-bottom: var(--sp-xl);
  border-bottom: 1px solid var(--color-border);
}

.filter-btn {
  padding: var(--sp-sm) var(--sp-md);
  font-size: 0.8125rem;
  font-weight: 400;
  color: var(--color-text-muted);
  border-bottom: 2px solid transparent;
  margin-bottom: -1px;
  transition: color 0.15s, border-color 0.15s;
}

.filter-btn:hover {
  color: var(--color-text);
}

.filter-btn--active,
.filter-btn.active {
  color: var(--color-text);
  border-bottom-color: var(--color-text);
  font-weight: 600;
}

/* Publication / course links */
.pub-link, .course-link {
  display: inline-block;
  font-size: 0.75rem;
  font-weight: 500;
  color: var(--color-link);
  padding: 2px 8px;
  border: 1px solid var(--color-border);
  border-radius: 3px;
  margin-right: 4px;
  transition: background 0.15s;
}

.pub-link:hover, .course-link:hover {
  background: var(--color-bg-alt);
  text-decoration: none;
}

/* ============================================================
   10. About Section
   ============================================================ */

.about-layout {
  display: flex;
  gap: var(--sp-2xl);
  align-items: flex-start;
}

.about-photo-col {
  flex-shrink: 0;
}

.profile-photo {
  width: 180px;
  height: auto;
  border-radius: 4px;
  border: 1px solid var(--color-border);
}

.about-content-col {
  flex: 1;
  min-width: 0;
}

.about-name-block {
  margin-bottom: var(--sp-lg);
}

.prof-name-ko {
  font-family: var(--font-heading);
  font-size: 1.75rem;
  font-weight: 700;
  color: var(--color-text);
  line-height: 1.2;
}

.prof-name-en {
  font-size: 0.9375rem;
  color: var(--color-text-muted);
  margin-top: 4px;
}

.prof-meta {
  margin-bottom: var(--sp-lg);
}

.prof-meta-row {
  display: flex;
  gap: var(--sp-md);
  padding: 4px 0;
  font-size: 0.875rem;
  line-height: 1.6;
}

.prof-meta-row dt {
  flex-shrink: 0;
  width: 50px;
  color: var(--color-text-muted);
  font-weight: 400;
}

.prof-meta-row dd {
  color: var(--color-text);
}

.prof-bio {
  margin-bottom: var(--sp-lg);
}

.prof-bio p {
  font-size: 0.875rem;
  line-height: 1.85;
  color: var(--color-text);
  margin-bottom: var(--sp-sm);
}

.prof-bio p:last-child {
  margin-bottom: 0;
}

.research-interests {
  margin-bottom: var(--sp-lg);
}

.interests-label {
  font-size: 0.8125rem;
  font-weight: 600;
  color: var(--color-text-muted);
  margin-bottom: var(--sp-sm);
  text-transform: uppercase;
  letter-spacing: 0.05em;
}

.external-links {
  display: flex;
  flex-wrap: wrap;
  gap: 0;
}

.text-muted {
  color: var(--color-text-muted);
}

/* ============================================================
   11. Research Section
   ============================================================ */

.card-grid {
  display: flex;
  flex-direction: column;
  gap: var(--sp-lg);
}

.project-card {
  padding: var(--sp-lg) 0;
  border: none;
  border-bottom: 1px solid var(--color-border);
  border-radius: 0;
  background: transparent;
}

.project-card:last-child {
  border-bottom: none;
}

.project-period {
  font-size: 0.8125rem;
  color: var(--color-text-muted);
  margin-bottom: var(--sp-xs);
}

.project-funding {
  font-size: 0.8125rem;
  color: var(--color-text-muted);
  margin-bottom: var(--sp-sm);
}

.project-description {
  font-size: 0.875rem;
  line-height: 1.7;
  color: var(--color-text);
  margin-bottom: var(--sp-sm);
}

/* ============================================================
   12. Publications Section
   ============================================================ */

.publications-list {
  display: flex;
  flex-direction: column;
  gap: var(--sp-xl);
}

.pub-year-group {
  margin-bottom: 0;
}

.pub-year-heading {
  font-family: var(--font-heading);
  font-size: 1.125rem;
  font-weight: 700;
  color: var(--color-text);
  margin-bottom: var(--sp-md);
  padding-bottom: var(--sp-xs);
  border-bottom: 1px solid var(--color-border);
}

.pub-list {
  display: flex;
  flex-direction: column;
  gap: var(--sp-md);
}

.pub-item {
  display: flex;
  gap: var(--sp-md);
  padding: var(--sp-sm) 0;
}

.pub-type-badge {
  flex-shrink: 0;
  font-size: 0.75rem;
  font-weight: 700;
  color: var(--color-text-muted);
  margin-top: 3px;
}

.pub-type--journal { color: #1d4ed8; }
.pub-type--conference { color: #065f46; }
.pub-type--book { color: #92400e; }

.pub-body {
  flex: 1;
  min-width: 0;
}

.pub-title {
  font-size: 0.875rem;
  font-weight: 600;
  color: var(--color-text);
  line-height: 1.5;
  margin-bottom: 2px;
}

.pub-authors {
  font-size: 0.8125rem;
  color: var(--color-text-muted);
  margin-bottom: 2px;
}

.pub-venue {
  font-size: 0.8125rem;
  color: var(--color-text);
  font-style: italic;
  margin-bottom: var(--sp-xs);
}

.pub-links {
  display: flex;
  flex-wrap: wrap;
  gap: 4px;
  margin-top: var(--sp-xs);
}

.bibtex-content {
  display: none;
}

/* ============================================================
   13. Teaching Section
   ============================================================ */

.semester-label {
  font-size: 0.8125rem;
  font-weight: 600;
  color: var(--color-text-muted);
  text-transform: uppercase;
  letter-spacing: 0.05em;
  margin-bottom: var(--sp-md);
}

.course-grid {
  gap: var(--sp-md);
}

.course-card {
  padding: var(--sp-lg);
  border: 1px solid var(--color-border);
  border-left: 3px solid var(--color-text-muted);
  border-radius: 0 4px 4px 0;
  background: var(--color-bg);
}

.course-card--current {
  border-left-color: var(--color-link);
}

.course-code {
  font-size: 0.75rem;
  color: var(--color-text-muted);
  font-family: var(--font-mono);
}

.course-meta {
  margin: var(--sp-sm) 0;
}

.course-meta-row {
  display: flex;
  gap: var(--sp-md);
  font-size: 0.8125rem;
  padding: 2px 0;
}

.course-meta-row dt {
  flex-shrink: 0;
  width: 45px;
  color: var(--color-text-muted);
}

.course-meta-row dd {
  color: var(--color-text);
}

.course-description {
  font-size: 0.8125rem;
  color: var(--color-text);
  line-height: 1.7;
  margin-bottom: var(--sp-sm);
}

.course-links {
  display: flex;
  gap: 4px;
}

/* Office Hours */
.office-hours-card {
  margin-top: var(--sp-xl);
  padding: var(--sp-lg);
  border: 1px solid var(--color-border);
  border-radius: 4px;
  background: var(--color-bg-alt);
}

.office-hours-card .card-title {
  font-size: 0.9375rem;
  margin-bottom: var(--sp-md);
  padding-bottom: var(--sp-sm);
  border-bottom: 1px solid var(--color-border);
}

/* Past courses */
.past-courses-details {
  margin-top: var(--sp-xl);
}

.details-summary {
  font-size: 0.875rem;
  font-weight: 500;
  color: var(--color-link);
  cursor: pointer;
  padding: var(--sp-sm) 0;
  list-style: none;
  border-bottom: 1px solid var(--color-border);
}

.details-summary::-webkit-details-marker { display: none; }
.details-summary::marker { display: none; content: ''; }

.details-summary::after {
  content: ' ▾';
  font-size: 0.75rem;
}

details[open] > .details-summary::after {
  content: ' ▴';
}

.past-courses-grid {
  padding-top: var(--sp-md);
}

.past-courses-grid .course-card {
  border-left-color: var(--color-border);
}

.course-semester {
  font-size: 0.75rem;
  color: var(--color-text-muted);
  margin-bottom: var(--sp-xs);
}

/* ============================================================
   14. Lab Section
   ============================================================ */

.lab-identity {
  margin-bottom: var(--sp-xl);
}

.lab-name {
  font-size: 1.125rem;
  font-weight: 700;
  color: var(--color-text);
  margin-bottom: var(--sp-sm);
}

.lab-name-en {
  display: block;
  font-size: 0.875rem;
  font-weight: 400;
  color: var(--color-text-muted);
  margin-top: 2px;
}

.lab-vision {
  font-size: 0.875rem;
  line-height: 1.8;
  color: var(--color-text);
  padding: var(--sp-md) var(--sp-lg);
  border-left: 3px solid var(--color-border);
  background: var(--color-bg-alt);
}

.lab-vision p {
  margin-bottom: var(--sp-sm);
}

.lab-vision p:last-child { margin-bottom: 0; }

.subsection-heading {
  font-size: 0.9375rem;
  font-weight: 700;
  color: var(--color-text);
  margin-bottom: var(--sp-md);
  text-transform: uppercase;
  letter-spacing: 0.03em;
}

.members-grid {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: var(--sp-md);
  margin-bottom: var(--sp-xl);
}

.member-card {
  text-align: center;
  padding: var(--sp-md);
  border: 1px solid var(--color-border);
  border-radius: 4px;
}

.member-photo {
  width: 72px;
  height: 72px;
  object-fit: cover;
  border-radius: 50%;
  margin: 0 auto var(--sp-sm);
  border: 1px solid var(--color-border);
}

.member-info {
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: 2px;
}

.member-name {
  font-size: 0.875rem;
  font-weight: 700;
  color: var(--color-text);
}

.member-role {
  font-size: 0.75rem;
  color: var(--color-text-muted);
}

.member-topic {
  font-size: 0.75rem;
  color: var(--color-text-light);
  line-height: 1.4;
}

.member-email {
  font-size: 0.75rem;
  color: var(--color-link);
}

/* Recruiting */
.recruiting-banner {
  padding: var(--sp-lg);
  border: 1px solid var(--color-border);
  border-radius: 4px;
  background: var(--color-bg-alt);
  margin-bottom: var(--sp-xl);
}

.recruiting-title {
  font-size: 1.0625rem;
  font-weight: 700;
  margin-bottom: var(--sp-sm);
}

.recruiting-intro {
  font-size: 0.875rem;
  color: var(--color-text-muted);
  margin-bottom: var(--sp-md);
}

.recruiting-positions {
  display: flex;
  flex-direction: column;
  gap: var(--sp-md);
}

.recruiting-position {
  padding: var(--sp-md);
  border: 1px solid var(--color-border);
  border-radius: 4px;
  background: var(--color-bg);
}

.position-type {
  font-size: 0.875rem;
  font-weight: 700;
  margin-bottom: var(--sp-xs);
}

.position-description {
  font-size: 0.8125rem;
  color: var(--color-text);
  margin-bottom: var(--sp-sm);
}

.requirements-label {
  font-size: 0.75rem;
  font-weight: 600;
  color: var(--color-text-muted);
  margin-bottom: var(--sp-xs);
}

.requirements-list {
  padding-left: var(--sp-lg);
  list-style: disc;
}

.requirements-list li {
  font-size: 0.8125rem;
  color: var(--color-text);
  line-height: 1.6;
}

.recruiting-contact {
  font-size: 0.8125rem;
  color: var(--color-text-muted);
  margin-top: var(--sp-md);
}

/* Alumni */
.alumni-details {
  margin-top: var(--sp-lg);
}

.alumni-list {
  padding-top: var(--sp-md);
}

.alumni-item {
  display: flex;
  align-items: baseline;
  gap: var(--sp-md);
  padding: var(--sp-xs) 0;
  border-bottom: 1px solid var(--color-border);
  font-size: 0.8125rem;
}

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

.alumni-name {
  font-weight: 600;
  color: var(--color-text);
}

.alumni-degree {
  color: var(--color-text-muted);
  font-size: 0.75rem;
}

.alumni-position {
  color: var(--color-text-light);
  font-size: 0.75rem;
  margin-left: auto;
  flex-shrink: 0;
}

/* ============================================================
   15. News Section
   ============================================================ */

.news-timeline {
  display: flex;
  flex-direction: column;
  gap: 0;
}

.news-item {
  display: flex;
  gap: var(--sp-md);
  padding: var(--sp-md) 0;
  border-bottom: 1px solid var(--color-border);
  align-items: flex-start;
}

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

.news-meta {
  flex-shrink: 0;
  min-width: 100px;
}

.news-date {
  display: block;
  font-size: 0.75rem;
  color: var(--color-text-muted);
  font-family: var(--font-mono);
}

.news-body {
  flex: 1;
  min-width: 0;
}

.news-title {
  font-size: 0.875rem;
  font-weight: 600;
  color: var(--color-text);
  line-height: 1.5;
}

a.news-title {
  color: var(--color-link);
}

a.news-title:hover {
  text-decoration: underline;
}

.news-description {
  font-size: 0.8125rem;
  color: var(--color-text-muted);
  line-height: 1.6;
  margin-top: 2px;
}

/* ============================================================
   16. Contact Section
   ============================================================ */

.contact-cards {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: var(--sp-md);
  margin-bottom: var(--sp-xl);
}

.contact-card {
  text-align: center;
  padding: var(--sp-lg);
  background: var(--color-bg-alt);
}

.contact-card-title {
  font-family: var(--font-body);
  font-size: 0.75rem;
  font-weight: 600;
  color: var(--color-text-muted);
  text-transform: uppercase;
  letter-spacing: 0.05em;
  margin-bottom: var(--sp-sm);
}

.contact-value {
  font-size: 0.9375rem;
  color: var(--color-text);
  font-weight: 500;
  margin-bottom: var(--sp-sm);
  display: block;
  word-break: break-all;
}

a.contact-value {
  color: var(--color-link);
}

.contact-guide {
  font-size: 0.75rem;
  color: var(--color-text-light);
  line-height: 1.5;
}

/* ============================================================
   17. Footer — Minimal
   ============================================================ */

.site-footer {
  border-top: 1px solid var(--color-border);
  padding-block: var(--sp-xl);
  background: var(--color-bg);
}

.footer-inner {
  display: flex;
  justify-content: space-between;
  align-items: flex-start;
  gap: var(--sp-xl);
}

.footer-info {
  flex: 1;
}

.footer-university {
  font-size: 0.8125rem;
  font-weight: 600;
  color: var(--color-text);
  margin-bottom: 2px;
}

.footer-department {
  font-size: 0.8125rem;
  color: var(--color-text-muted);
  margin-bottom: var(--sp-sm);
}

.footer-contact-list {
  display: flex;
  flex-wrap: wrap;
  gap: var(--sp-md);
}

.footer-contact-item {
  display: flex;
  gap: var(--sp-xs);
  font-size: 0.75rem;
}

.footer-contact-item dt {
  color: var(--color-text-muted);
  font-weight: 500;
}

.footer-contact-item dd {
  color: var(--color-text);
}

.footer-contact-item a {
  color: var(--color-link);
}

.footer-meta {
  text-align: right;
  flex-shrink: 0;
}

.footer-updated {
  font-size: 0.6875rem;
  color: var(--color-text-light);
}

.footer-copyright {
  font-size: 0.6875rem;
  color: var(--color-text-light);
  margin-top: 2px;
}

/* ============================================================
   18. Empty state
   ============================================================ */

.empty-message {
  font-size: 0.875rem;
  color: var(--color-text-muted);
  padding: var(--sp-lg) 0;
}

/* ============================================================
   19. Focus Styles
   ============================================================ */

:focus-visible {
  outline: 2px solid var(--color-link);
  outline-offset: 2px;
}

/* ============================================================
   20. Print
   ============================================================ */

@media print {
  .site-header,
  .hamburger,
  .filter-bar,
  .pub-link--bibtex,
  .course-link,
  .recruiting-banner,
  .site-footer {
    display: none !important;
  }

  body {
    color: #000;
    background: #fff;
    font-size: 10pt;
    line-height: 1.5;
  }

  h1, h2, h3 { color: #000; }

  a { color: #000; }

  a[href^="http"]::after {
    content: " (" attr(href) ")";
    font-size: 0.7em;
    color: #666;
  }

  section {
    padding-block: 1rem;
    border-top: 1px solid #ccc;
  }

  .container {
    max-width: 100%;
    padding-inline: 0;
  }
}

/* ============================================================
   Back to Top Buttons
   ============================================================ */

/* Section-level back-to-top link */
.btn-back-to-top {
  display: inline-flex;
  align-items: center;
  gap: 4px;
  margin-top: var(--sp-lg);
  padding: 6px 14px;
  font-size: 0.8125rem;
  color: var(--color-text-muted);
  background: var(--color-bg-alt);
  border: 1px solid var(--color-border);
  border-radius: 16px;
  text-decoration: none;
  transition: color 0.2s, background 0.2s, border-color 0.2s;
}

.btn-back-to-top:hover {
  color: #fff;
  background: var(--color-link);
  border-color: var(--color-link);
  text-decoration: none;
}

/* Floating back-to-top button */
.floating-top-btn {
  position: fixed;
  bottom: 28px;
  right: 28px;
  width: 44px;
  height: 44px;
  display: flex;
  align-items: center;
  justify-content: center;
  background: var(--color-link);
  color: #fff;
  border: none;
  border-radius: 50%;
  font-size: 1.25rem;
  cursor: pointer;
  box-shadow: 0 2px 8px rgba(0, 0, 0, 0.2);
  opacity: 0;
  visibility: hidden;
  transition: opacity 0.3s, visibility 0.3s, background 0.2s;
  z-index: 900;
}

.floating-top-btn.visible {
  opacity: 1;
  visibility: visible;
}

.floating-top-btn:hover {
  background: var(--color-link-hover);
}

/* ============================================================
   Conversation Banner — Teaching section
   ============================================================ */

.conversation-banner {
  margin-top: var(--sp-xl);
  padding: var(--sp-lg) var(--sp-xl);
  background: var(--color-bg-alt);
  border: 1px solid var(--color-border);
  border-left: 4px solid var(--color-link);
  border-radius: 4px;
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  gap: var(--sp-md);
}

.conversation-banner h3 {
  font-size: 1.05rem;
  font-weight: 700;
  margin: 0;
  flex: 1 1 auto;
}

.conversation-banner p {
  font-size: 0.875rem;
  color: var(--color-text-muted);
  margin: 0;
  flex: 1 1 200px;
}

.btn-conversation {
  display: inline-block;
  padding: 0.45rem 1.1rem;
  background: var(--color-link);
  color: #fff;
  border-radius: 4px;
  font-size: 0.875rem;
  font-weight: 700;
  text-decoration: none;
  white-space: nowrap;
  transition: background 0.15s;
}

.btn-conversation:hover {
  background: var(--color-link-hover);
  text-decoration: none;
  color: #fff;
}