/* ===================================================
   COLLAB-REC Project Website — Main Stylesheet
   Modular, responsive, no duplication
   =================================================== */

/* --- 1. Google Fonts Import --- */
@import url('https://fonts.googleapis.com/css2?family=Google+Sans:wght@400;500;700&family=Noto+Sans:wght@400;500;700&family=Source+Code+Pro&display=swap');

/* --- 2. CSS Custom Properties (Design Tokens) --- */
:root {
  /* Colors */
  --color-primary:        hsl(204, 86%, 53%);
  --color-primary-dark:   hsl(204, 86%, 38%);
  --color-accent:         hsl(340, 82%, 52%);
  --color-dark:           hsl(220, 20%, 12%);
  --color-dark-secondary: hsl(220, 15%, 18%);
  --color-text:           hsl(220, 15%, 20%);
  --color-text-light:     hsl(220, 10%, 45%);
  --color-border:         hsl(220, 15%, 88%);
  --color-bg:             hsl(0, 0%, 100%);
  --color-bg-alt:         hsl(220, 20%, 97%);
  --color-success:        hsl(142, 72%, 29%);
  --color-tag-bg:         hsl(204, 86%, 94%);

  /* Typography */
  --font-title:   'Google Sans', 'Noto Sans', sans-serif;
  --font-body:    'Noto Sans', sans-serif;
  --font-mono:    'Source Code Pro', monospace;

  /* Spacing */
  --space-xs:   0.25rem;
  --space-sm:   0.5rem;
  --space-md:   1rem;
  --space-lg:   2rem;
  --space-xl:   3rem;
  --space-2xl:  5rem;

  /* Layout */
  --max-width:        960px;
  --max-width-wide:   1200px;
  --border-radius:    10px;
  --border-radius-lg: 20px;

  /* Shadows */
  --shadow-sm:  0 2px 8px rgba(0,0,0,0.08);
  --shadow-md:  0 6px 20px rgba(0,0,0,0.10);
  --shadow-lg:  0 12px 40px rgba(0,0,0,0.13);

  /* Transitions */
  --transition: 0.2s ease;
}

/* --- 3. Reset & Base --- */
*, *::before, *::after {
  box-sizing: border-box;
  margin: 0;
  padding: 0;
}

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

body {
  font-family: var(--font-body);
  color: var(--color-text);
  background: var(--color-bg);
  line-height: 1.7;
  -webkit-font-smoothing: antialiased;
}

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

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

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

/* --- 4. Layout Utilities --- */
.container {
  width: 100%;
  max-width: var(--max-width);
  margin-inline: auto;
  padding-inline: var(--space-lg);
}

.container--wide {
  max-width: var(--max-width-wide);
}

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

.section--alt {
  background: var(--color-bg-alt);
}

.text-center { text-align: center; }
.text-left   { text-align: left; }

/* --- 5. Typography --- */
h1, h2, h3, h4, h5 {
  font-family: var(--font-title);
  line-height: 1.25;
  color: var(--color-dark);
}

h1 { font-size: clamp(1.75rem, 4vw, 2.5rem); font-weight: 700; }
h2 { font-size: clamp(1.4rem, 3vw, 2rem);    font-weight: 700; }
h3 { font-size: clamp(1.1rem, 2.5vw, 1.4rem); font-weight: 500; }
h4 { font-size: 1rem; font-weight: 700; }

.section-title {
  font-family: var(--font-title);
  font-size: clamp(1.4rem, 3vw, 2rem);
  font-weight: 700;
  color: var(--color-dark);
  margin-bottom: var(--space-md);
}

.section-divider {
  display: flex;
  align-items: center;
  justify-content: center;
  gap: var(--space-md);
  margin-bottom: var(--space-xl);
}

.section-divider::before,
.section-divider::after {
  content: '';
  flex: 1;
  max-width: 80px;
  height: 2px;
  background: var(--color-border);
}

p {
  max-width: 75ch;
}

/* --- 6. Navigation --- */
.navbar {
  position: sticky;
  top: 0;
  z-index: 100;
  background: rgba(255, 255, 255, 0.95);
  backdrop-filter: blur(10px);
  border-bottom: 1px solid var(--color-border);
  padding-block: var(--space-md);
}

.navbar__inner {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: var(--space-md);
  max-width: var(--max-width);
  margin-inline: auto;
  padding-inline: var(--space-lg);
}

.navbar__brand {
  font-family: var(--font-title);
  font-weight: 700;
  font-size: 1.1rem;
  color: var(--color-dark);
  white-space: nowrap;
}

.navbar__brand span {
  color: var(--color-primary);
}

.navbar__links {
  display: flex;
  align-items: center;
  gap: var(--space-lg);
  list-style: none;
}

.navbar__links a {
  font-size: 0.9rem;
  font-weight: 500;
  color: var(--color-text-light);
  transition: color var(--transition);
}

.navbar__links a:hover {
  color: var(--color-primary);
  text-decoration: none;
}

.navbar__toggle {
  display: none;
  background: none;
  border: none;
  cursor: pointer;
  font-size: 1.4rem;
  color: var(--color-dark);
  padding: var(--space-xs);
}

/* --- 7. Hero Section --- */
.hero {
  padding-block: var(--space-2xl);
  text-align: center;
  background: linear-gradient(180deg, hsl(220, 30%, 98%) 0%, var(--color-bg) 100%);
  border-bottom: 1px solid var(--color-border);
}

.hero__venue-badge {
  display: inline-block;
  background: var(--color-tag-bg);
  color: var(--color-primary-dark);
  font-weight: 700;
  font-size: 0.85rem;
  padding: var(--space-xs) var(--space-md);
  border-radius: 100px;
  margin-bottom: var(--space-lg);
  border: 1px solid hsl(204, 86%, 80%);
  font-family: var(--font-title);
  letter-spacing: 0.02em;
  text-transform: uppercase;
}

.hero__title {
  font-size: clamp(1.6rem, 4.5vw, 2.8rem);
  font-weight: 700;
  color: var(--color-dark);
  max-width: 800px;
  margin-inline: auto;
  margin-bottom: var(--space-lg);
  line-height: 1.2;
}

.hero__title .highlight {
  color: var(--color-primary);
}

.hero__authors {
  font-family: var(--font-title);
  font-size: 1rem;
  color: var(--color-text-light);
  margin-bottom: var(--space-sm);
}

.hero__authors a {
  color: var(--color-primary);
  font-weight: 500;
}

.hero__authors a:hover {
  color: var(--color-primary-dark);
}

.author-block {
  display: inline-block;
}

.author-block sup {
  font-size: 0.65em;
}

.hero__affiliations {
  font-family: var(--font-title);
  font-size: 0.9rem;
  color: var(--color-text-light);
  margin-bottom: var(--space-xl);
}

.hero__affiliations sup {
  font-size: 0.7em;
}

/* --- 8. Button Group (Link Badges) --- */
.btn-group {
  display: flex;
  flex-wrap: wrap;
  justify-content: center;
  gap: var(--space-sm);
  margin-top: var(--space-lg);
}

.btn {
  display: inline-flex;
  align-items: center;
  gap: var(--space-xs);
  padding: 0.45rem 1.1rem;
  border-radius: 100px;
  font-size: 0.875rem;
  font-weight: 500;
  font-family: var(--font-title);
  transition: all var(--transition);
  border: 2px solid transparent;
  cursor: pointer;
  text-decoration: none !important;
  white-space: nowrap;
}

.btn--dark {
  background: var(--color-dark);
  color: #fff;
  border-color: var(--color-dark);
}

.btn--dark:hover {
  background: var(--color-dark-secondary);
  color: #fff;
  transform: translateY(-1px);
  box-shadow: var(--shadow-sm);
}

.btn--outline {
  background: transparent;
  color: var(--color-dark);
  border-color: var(--color-border);
}

.btn--outline:hover {
  border-color: var(--color-primary);
  color: var(--color-primary);
  transform: translateY(-1px);
}

.btn i, .btn .btn-icon {
  font-size: 0.9em;
}

/* --- 9. Teaser / Banner Image --- */
.teaser {
  padding-block: var(--space-xl);
  text-align: center;
}

.teaser__figure {
  max-width: 820px;
  margin-inline: auto;
}

.teaser__img {
  width: 100%;
  border-radius: var(--border-radius-lg);
  box-shadow: var(--shadow-lg);
  border: 1px solid var(--color-border);
  background: var(--color-bg-alt);
}

/* Placeholder image styling */
.placeholder-img {
  background: linear-gradient(135deg, hsl(220, 20%, 92%) 0%, hsl(220, 25%, 85%) 100%);
  display: flex;
  flex-direction: column;
  align-items: center;
  justify-content: center;
  color: var(--color-text-light);
  font-family: var(--font-title);
  gap: var(--space-sm);
  border-radius: var(--border-radius-lg);
  border: 2px dashed var(--color-border);
}

.placeholder-img i {
  font-size: 3rem;
  opacity: 0.4;
}

.placeholder-img span {
  font-size: 0.85rem;
  opacity: 0.6;
}

.teaser__caption {
  font-size: 0.875rem;
  color: var(--color-text-light);
  margin-top: var(--space-md);
  font-style: italic;
  max-width: 680px;
  margin-inline: auto;
}

/* --- 10. Abstract Section --- */
.abstract-box {
  background: var(--color-bg);
  border: 1px solid var(--color-border);
  border-radius: var(--border-radius-lg);
  padding: var(--space-xl);
  box-shadow: var(--shadow-sm);
  max-width: 800px;
  margin-inline: auto;
}

.abstract-box p {
  font-size: 1rem;
  line-height: 1.8;
  color: var(--color-text);
  max-width: none;
}

/* --- 11. Contributions / Key Points --- */
.contributions-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(260px, 1fr));
  gap: var(--space-lg);
  margin-top: var(--space-xl);
}

.contribution-card {
  background: var(--color-bg);
  border: 1px solid var(--color-border);
  border-radius: var(--border-radius-lg);
  padding: var(--space-lg);
  box-shadow: var(--shadow-sm);
  transition: box-shadow var(--transition), transform var(--transition);
  display: flex;
  flex-direction: column;
  gap: var(--space-sm);
}

.contribution-card:hover {
  box-shadow: var(--shadow-md);
  transform: translateY(-3px);
}

.contribution-card__icon {
  width: 48px;
  height: 48px;
  border-radius: var(--border-radius);
  background: var(--color-tag-bg);
  display: flex;
  align-items: center;
  justify-content: center;
  color: var(--color-primary);
  font-size: 1.4rem;
  margin-bottom: var(--space-sm);
  flex-shrink: 0;
}

.contribution-card__title {
  font-family: var(--font-title);
  font-weight: 700;
  font-size: 1rem;
  color: var(--color-dark);
}

.contribution-card__text {
  font-size: 0.9rem;
  color: var(--color-text-light);
  line-height: 1.6;
  max-width: none;
}

/* --- 12. Framework / Architecture Section --- */
.framework-figure {
  margin-top: var(--space-xl);
  text-align: center;
}

.framework-figure figcaption {
  font-size: 0.875rem;
  color: var(--color-text-light);
  margin-top: var(--space-md);
  font-style: italic;
  max-width: 700px;
  margin-inline: auto;
}

/* --- 13. Agent Cards --- */
.agents-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(260px, 1fr));
  gap: var(--space-lg);
  margin-top: var(--space-xl);
}

.agent-card {
  background: var(--color-bg);
  border: 1px solid var(--color-border);
  border-radius: var(--border-radius-lg);
  padding: var(--space-lg);
  box-shadow: var(--shadow-sm);
  transition: box-shadow var(--transition), transform var(--transition);
  border-top: 4px solid var(--agent-color, var(--color-primary));
}

.agent-card:hover {
  box-shadow: var(--shadow-md);
  transform: translateY(-3px);
}

.agent-card--personalization { --agent-color: hsl(204, 86%, 53%); }
.agent-card--popularity      { --agent-color: hsl(35, 90%, 52%); }
.agent-card--sustainability   { --agent-color: hsl(142, 60%, 40%); }

.agent-card__tag {
  display: inline-block;
  font-size: 0.75rem;
  font-weight: 700;
  font-family: var(--font-title);
  text-transform: uppercase;
  letter-spacing: 0.05em;
  padding: 0.2rem 0.6rem;
  border-radius: 100px;
  background: color-mix(in srgb, var(--agent-color) 15%, transparent);
  color: var(--agent-color);
  margin-bottom: var(--space-sm);
}

.agent-card__name {
  font-family: var(--font-title);
  font-weight: 700;
  font-size: 1.1rem;
  color: var(--color-dark);
  margin-bottom: var(--space-sm);
}

.agent-card__text {
  font-size: 0.9rem;
  color: var(--color-text-light);
  line-height: 1.65;
  max-width: none;
}

/* --- 14. Results / Figures Section --- */
.results-figures {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(300px, 1fr));
  gap: var(--space-lg);
  margin-top: var(--space-xl);
}

.result-figure {
  text-align: center;
}

.result-figure__img {
  width: 100%;
  border-radius: var(--border-radius);
  border: 1px solid var(--color-border);
  background: var(--color-bg-alt);
  box-shadow: var(--shadow-sm);
}

.result-figure__caption {
  font-size: 0.8rem;
  color: var(--color-text-light);
  margin-top: var(--space-sm);
  font-style: italic;
}

/* --- 15. Metrics / Stats Row --- */
.stats-row {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(160px, 1fr));
  gap: var(--space-lg);
  margin-top: var(--space-xl);
  text-align: center;
}

.stat-item__number {
  font-family: var(--font-title);
  font-size: 2.2rem;
  font-weight: 700;
  color: var(--color-primary);
  line-height: 1;
  margin-bottom: var(--space-xs);
}

.stat-item__label {
  font-size: 0.85rem;
  color: var(--color-text-light);
  font-weight: 500;
}

/* --- 16. BibTeX Section --- */
.bibtex-box {
  background: hsl(220, 20%, 13%);
  color: hsl(220, 20%, 80%);
  border-radius: var(--border-radius-lg);
  padding: var(--space-xl);
  font-family: var(--font-mono);
  font-size: 0.85rem;
  line-height: 1.7;
  overflow-x: auto;
  position: relative;
  max-width: 800px;
  margin-inline: auto;
  box-shadow: var(--shadow-lg);
}

.bibtex-box pre {
  white-space: pre;
  overflow-x: auto;
}

.copy-btn {
  position: absolute;
  top: var(--space-md);
  right: var(--space-md);
  background: rgba(255,255,255,0.1);
  border: 1px solid rgba(255,255,255,0.2);
  color: #fff;
  border-radius: var(--border-radius);
  padding: 0.3rem 0.8rem;
  font-size: 0.8rem;
  font-family: var(--font-body);
  cursor: pointer;
  transition: background var(--transition);
}

.copy-btn:hover {
  background: rgba(255,255,255,0.2);
}

.copy-btn.copied {
  background: rgba(34, 197, 94, 0.3);
  border-color: rgba(34, 197, 94, 0.5);
}

/* Syntax highlighting for bibtex */
.bibtex-key   { color: hsl(204, 86%, 75%); }
.bibtex-value { color: hsl(35, 90%, 70%); }
.bibtex-type  { color: hsl(280, 70%, 75%); }
.bibtex-brace { color: hsl(220, 20%, 65%); }

/* --- 17. Footer --- */
.footer {
  background: var(--color-dark);
  color: hsl(220, 15%, 65%);
  padding-block: var(--space-xl);
  text-align: center;
  font-size: 0.875rem;
}

.footer p {
  text-align: center;
  margin: 0 auto;
}

.footer a {
  color: hsl(220, 15%, 75%);
}

.footer a:hover {
  color: var(--color-primary);
}

.footer__icon-links {
  display: flex;
  justify-content: center;
  gap: var(--space-lg);
  margin-bottom: var(--space-md);
}

.footer__icon-links a {
  font-size: 1.4rem;
  color: hsl(220, 15%, 55%);
  transition: color var(--transition);
}

.footer__icon-links a:hover {
  color: var(--color-primary);
}

/* --- 18. Responsive Breakpoints --- */
@media (max-width: 768px) {
  :root {
    --space-2xl: 3rem;
    --space-xl:  2rem;
    --space-lg:  1.25rem;
  }

  .navbar__links {
    display: none;
    flex-direction: column;
    position: absolute;
    top: 100%;
    left: 0;
    right: 0;
    background: var(--color-bg);
    border-bottom: 1px solid var(--color-border);
    padding: var(--space-md) var(--space-lg);
    gap: var(--space-md);
    box-shadow: var(--shadow-md);
  }

  .navbar__links.is-open {
    display: flex;
  }

  .navbar__toggle {
    display: block;
  }

  .navbar__inner {
    position: relative;
  }

  .contributions-grid,
  .agents-grid {
    grid-template-columns: 1fr;
  }

  .results-figures {
    grid-template-columns: 1fr;
  }

  .stats-row {
    grid-template-columns: repeat(2, 1fr);
  }

  .abstract-box {
    padding: var(--space-lg);
  }

  .bibtex-box {
    font-size: 0.78rem;
    padding: var(--space-lg);
  }

  .hero__title {
    font-size: clamp(1.4rem, 6vw, 2rem);
  }
}

@media (max-width: 480px) {
  .stats-row {
    grid-template-columns: 1fr;
  }

  .btn-group {
    flex-direction: column;
    align-items: center;
  }
}

/* --- 19. Scroll-to-top button --- */
.scroll-top {
  position: fixed;
  bottom: var(--space-lg);
  right: var(--space-lg);
  width: 42px;
  height: 42px;
  border-radius: 50%;
  background: var(--color-primary);
  color: #fff;
  border: none;
  cursor: pointer;
  font-size: 1rem;
  display: flex;
  align-items: center;
  justify-content: center;
  box-shadow: var(--shadow-md);
  opacity: 0;
  pointer-events: none;
  transition: opacity var(--transition), transform var(--transition);
  z-index: 99;
}

.scroll-top.is-visible {
  opacity: 1;
  pointer-events: auto;
}

.scroll-top:hover {
  transform: translateY(-3px);
  box-shadow: var(--shadow-lg);
}

/* --- 20. Accessibility: focus styles --- */
a:focus-visible,
button:focus-visible {
  outline: 3px solid var(--color-primary);
  outline-offset: 3px;
  border-radius: 4px;
}

/* --- 21. Teaser real image --- */
.teaser__img {
  display: block;
  width: 100%;
  max-width: 900px;
  margin-inline: auto;
  border-radius: var(--border-radius-lg);
  box-shadow: var(--shadow-lg);
  border: 1px solid var(--color-border);
}

/* --- 22. Result subsections (RQ1–RQ5) --- */
.result-subsection {
  margin-bottom: var(--space-xl);
}

.result-subsection__title {
  font-family: var(--font-title);
  font-size: 1.15rem;
  font-weight: 700;
  color: var(--color-dark);
  margin-bottom: var(--space-sm);
  text-align: center;
}

.result-subsection__desc {
  text-align: center;
  color: var(--color-text-light);
  font-size: 0.9rem;
  max-width: 700px;
  margin-inline: auto;
  margin-bottom: var(--space-lg);
}

/* --- 23. Model tab switcher --- */
.plot-tabs {
  display: flex;
  flex-wrap: wrap;
  gap: var(--space-sm);
  justify-content: center;
  margin-bottom: var(--space-md);
}

.plot-tab {
  padding: 0.35rem 0.9rem;
  border: 1px solid var(--color-border);
  border-radius: 100px;
  background: var(--color-bg);
  color: var(--color-text-light);
  font-family: var(--font-title);
  font-size: 0.82rem;
  font-weight: 600;
  cursor: pointer;
  transition: background var(--transition), color var(--transition), border-color var(--transition);
}

.plot-tab:hover {
  background: var(--color-bg-alt);
  color: var(--color-dark);
  border-color: var(--color-primary);
}

.plot-tab.is-active {
  background: var(--color-primary);
  color: #fff;
  border-color: var(--color-primary);
}

/* --- 24. Plot panels (tab content areas) --- */
.plot-panels {
  position: relative;
}

.plot-panel {
  display: none;
}

.plot-panel.is-active {
  display: block;
}

/* --- 25. PDF embed via <object> --- */
.pdf-embed {
  display: block;
  width: 100%;
  height: 420px;
  border-radius: var(--border-radius);
  border: 1px solid var(--color-border);
  box-shadow: var(--shadow-sm);
  background: var(--color-bg-alt);
}

/* --- 26. Plot legend strip --- */
.plot-legend {
  display: flex;
  justify-content: center;
  margin-top: var(--space-md);
}

.plot-legend img {
  max-height: 70px;
  width: auto;
  border-radius: var(--border-radius);
  border: 1px solid var(--color-border);
  padding: 0.25rem 0.5rem;
  background: var(--color-bg);
}

/* --- 27. result-figure img (for PNG results) --- */
.result-figure__img {
  display: block;
  width: 100%;
  border-radius: var(--border-radius-lg);
  border: 1px solid var(--color-border);
  box-shadow: var(--shadow-md);
}

/* --- 28. Framework figure: center the img --- */
.framework-figure img {
  display: block;
  width: 100%;
}