/* =========================================================
   IROS 2026 Workshop — Compositional & Modular Learning
   Main Stylesheet
   ========================================================= */

/* ---- CSS Variables ---- */
:root {
  --color-primary: #1a56db;
  --color-primary-dark: #1342b0;
  --color-primary-light: #e8f0fe;
  --color-secondary: #0d9488;
  --color-accent: #f59e0b;

  --color-bg: #ffffff;
  --color-bg-alt: #f8fafc;
  --color-surface: #ffffff;
  --color-border: #e2e8f0;

  --color-text: #1e293b;
  --color-text-secondary: #475569;
  --color-text-muted: #94a3b8;

  --color-hero-start: #0f172a;
  --color-hero-end: #1e3a5f;

  --font-sans: 'Inter', system-ui, -apple-system, sans-serif;
  --font-serif: 'Source Serif 4', Georgia, serif;

  --radius-sm: 6px;
  --radius-md: 10px;
  --radius-lg: 16px;
  --radius-xl: 24px;

  --shadow-sm: 0 1px 3px rgba(0, 0, 0, 0.08), 0 1px 2px rgba(0, 0, 0, 0.04);
  --shadow-md: 0 4px 12px rgba(0, 0, 0, 0.10), 0 2px 4px rgba(0, 0, 0, 0.06);
  --shadow-lg: 0 10px 30px rgba(0, 0, 0, 0.12), 0 4px 8px rgba(0, 0, 0, 0.06);

  --nav-height: 64px;
  --container-max: 1140px;
  --section-padding: 80px;
}

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

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

body {
  font-family: var(--font-sans);
  color: var(--color-text);
  background: var(--color-bg);
  line-height: 1.6;
  -webkit-font-smoothing: antialiased;
}

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

a {
  color: var(--color-primary);
  text-decoration: none;
  transition: color 0.2s;
}

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

ul {
  list-style: none;
}

/* ---- Utility ---- */
.container {
  max-width: var(--container-max);
  margin: 0 auto;
  padding: 0 24px;
}

.section {
  padding: var(--section-padding) 0;
}

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

.section-header {
  text-align: center;
  margin-bottom: 56px;
}

.section-tag {
  display: inline-block;
  font-size: 0.75rem;
  font-weight: 600;
  letter-spacing: 0.1em;
  text-transform: uppercase;
  color: var(--color-primary);
  background: var(--color-primary-light);
  padding: 4px 12px;
  border-radius: 100px;
  margin-bottom: 12px;
}

.section-title {
  font-family: var(--font-serif);
  font-size: clamp(1.75rem, 3vw, 2.5rem);
  font-weight: 600;
  color: var(--color-text);
  line-height: 1.2;
  margin-bottom: 16px;
}

.section-desc {
  font-size: 1.05rem;
  color: var(--color-text-secondary);
  max-width: 640px;
  margin: 0 auto;
}

/* ---- Buttons ---- */
.btn {
  display: inline-flex;
  align-items: center;
  gap: 8px;
  padding: 12px 24px;
  border-radius: var(--radius-md);
  font-family: var(--font-sans);
  font-size: 0.95rem;
  font-weight: 600;
  cursor: pointer;
  transition: all 0.2s;
  text-decoration: none;
  border: 2px solid transparent;
}

.btn-primary {
  background: var(--color-primary);
  color: #ffffff;
  border-color: var(--color-primary);
}

.btn-primary:hover {
  background: var(--color-primary-dark);
  border-color: var(--color-primary-dark);
  color: #ffffff;
  transform: translateY(-1px);
  box-shadow: var(--shadow-md);
}

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

.btn-outline:hover {
  background: var(--color-primary-light);
  color: var(--color-primary-dark);
}

.btn-sm {
  padding: 8px 18px;
  font-size: 0.875rem;
}

.btn-disabled {
  opacity: 0.55;
  cursor: not-allowed;
  pointer-events: none;
}

/* ---- Navbar ---- */
.navbar {
  position: fixed;
  top: 0;
  left: 0;
  right: 0;
  height: var(--nav-height);
  background: rgba(15, 23, 42, 0.97);
  backdrop-filter: blur(12px);
  -webkit-backdrop-filter: blur(12px);
  z-index: 1000;
  border-bottom: 1px solid rgba(255, 255, 255, 0.08);
  transition: box-shadow 0.3s;
}

.navbar.scrolled {
  box-shadow: 0 4px 24px rgba(0, 0, 0, 0.25);
}

.nav-container {
  max-width: var(--container-max);
  margin: 0 auto;
  padding: 0 24px;
  height: 100%;
  display: flex;
  align-items: center;
  justify-content: space-between;
}

.nav-brand {
  font-size: 0.95rem;
  font-weight: 700;
  color: #ffffff;
  letter-spacing: 0.01em;
  white-space: nowrap;
}

.nav-brand:hover {
  color: rgba(255, 255, 255, 0.85);
}

.nav-links {
  display: flex;
  align-items: center;
  gap: 8px;
}

.nav-links a {
  color: rgba(255, 255, 255, 0.8);
  font-size: 0.875rem;
  font-weight: 500;
  padding: 6px 12px;
  border-radius: var(--radius-sm);
  transition: all 0.2s;
}

.nav-links a:hover,
.nav-links a.active {
  color: #ffffff;
  background: rgba(255, 255, 255, 0.1);
}

.nav-toggle {
  display: none;
  flex-direction: column;
  gap: 5px;
  background: none;
  border: none;
  cursor: pointer;
  padding: 4px;
}

.nav-toggle span {
  display: block;
  width: 22px;
  height: 2px;
  background: #ffffff;
  border-radius: 2px;
  transition: all 0.3s;
}

/* ---- Hero ---- */
.hero {
  min-height: 100vh;
  background: linear-gradient(135deg, var(--color-hero-start) 0%, var(--color-hero-end) 60%, #1a4d6e 100%);
  display: flex;
  flex-direction: column;
  align-items: center;
  justify-content: center;
  position: relative;
  overflow: hidden;
  padding: calc(var(--nav-height) + 40px) 24px 80px;
}

.hero::before {
  content: '';
  position: absolute;
  inset: 0;
  background:
    radial-gradient(ellipse 70% 60% at 80% 20%, rgba(26, 86, 219, 0.18) 0%, transparent 60%),
    radial-gradient(ellipse 50% 40% at 20% 80%, rgba(13, 148, 136, 0.12) 0%, transparent 55%);
  pointer-events: none;
}

/* Animated grid overlay */
.hero::after {
  content: '';
  position: absolute;
  inset: 0;
  background-image:
    linear-gradient(rgba(255,255,255,0.03) 1px, transparent 1px),
    linear-gradient(90deg, rgba(255,255,255,0.03) 1px, transparent 1px);
  background-size: 48px 48px;
  pointer-events: none;
}

.hero-overlay {
  position: absolute;
  inset: 0;
  background: rgba(0, 0, 0, 0.2);
}

.hero-content {
  position: relative;
  z-index: 2;
  text-align: center;
  max-width: 860px;
}

.conference-badge {
  display: inline-flex;
  align-items: center;
  gap: 8px;
  padding: 6px 18px;
  background: rgba(245, 158, 11, 0.15);
  border: 1px solid rgba(245, 158, 11, 0.4);
  border-radius: 100px;
  color: #fbbf24;
  font-size: 0.8rem;
  font-weight: 700;
  letter-spacing: 0.08em;
  text-transform: uppercase;
  margin-bottom: 24px;
}

.hero-title {
  font-family: var(--font-serif);
  font-size: clamp(1.8rem, 4.5vw, 3.5rem);
  font-weight: 600;
  color: #ffffff;
  line-height: 1.15;
  margin-bottom: 24px;
  text-shadow: 0 2px 20px rgba(0,0,0,0.3);
}

.hero-subtitle {
  font-size: 1rem;
  color: rgba(255, 255, 255, 0.7);
  margin-bottom: 32px;
}

.hero-subtitle a {
  color: rgba(255, 255, 255, 0.8);
  border-bottom: 1px solid rgba(255,255,255,0.3);
  padding-bottom: 1px;
  transition: all 0.2s;
}

.hero-subtitle a:hover {
  color: #ffffff;
  border-color: rgba(255,255,255,0.7);
}

.hero-meta {
  display: flex;
  align-items: center;
  justify-content: center;
  gap: 32px;
  margin-bottom: 40px;
  flex-wrap: wrap;
}

.hero-meta-item {
  display: flex;
  align-items: center;
  gap: 8px;
  color: rgba(255, 255, 255, 0.75);
  font-size: 0.95rem;
  font-weight: 500;
}

.hero-meta-item svg {
  width: 18px;
  height: 18px;
  opacity: 0.7;
}

.hero-actions {
  display: flex;
  align-items: center;
  justify-content: center;
  gap: 16px;
  flex-wrap: wrap;
}

.hero .btn-primary {
  background: var(--color-primary);
  border-color: var(--color-primary);
  font-size: 1rem;
  padding: 14px 32px;
}

.hero .btn-outline {
  border-color: rgba(255,255,255,0.5);
  color: rgba(255,255,255,0.9);
  font-size: 1rem;
  padding: 14px 32px;
}

.hero .btn-outline:hover {
  background: rgba(255,255,255,0.12);
  border-color: rgba(255,255,255,0.75);
  color: #ffffff;
}

.hero-scroll-indicator {
  position: absolute;
  bottom: 32px;
  left: 50%;
  transform: translateX(-50%);
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: 6px;
  color: rgba(255,255,255,0.45);
  font-size: 0.75rem;
  letter-spacing: 0.05em;
  animation: bounce 2s infinite;
  z-index: 2;
}

.hero-scroll-indicator svg {
  width: 20px;
  height: 20px;
}

@keyframes bounce {
  0%, 100% { transform: translateX(-50%) translateY(0); }
  50% { transform: translateX(-50%) translateY(6px); }
}

/* ---- Overview ---- */
.overview-grid {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 56px;
  align-items: start;
}

.overview-text p {
  color: var(--color-text-secondary);
  margin-bottom: 16px;
  line-height: 1.75;
  font-size: 1rem;
}

.overview-focus h3 {
  font-family: var(--font-serif);
  font-size: 1.4rem;
  font-weight: 600;
  margin-bottom: 24px;
  color: var(--color-text);
}

.focus-card {
  display: flex;
  gap: 16px;
  align-items: flex-start;
  padding: 20px;
  background: var(--color-bg);
  border: 1px solid var(--color-border);
  border-radius: var(--radius-lg);
  margin-bottom: 16px;
  box-shadow: var(--shadow-sm);
  transition: box-shadow 0.25s, transform 0.25s;
}

.focus-card:hover {
  box-shadow: var(--shadow-md);
  transform: translateY(-2px);
}

.focus-icon {
  width: 44px;
  height: 44px;
  border-radius: var(--radius-md);
  background: var(--color-primary-light);
  display: flex;
  align-items: center;
  justify-content: center;
  flex-shrink: 0;
}

.focus-icon svg {
  width: 22px;
  height: 22px;
  stroke: var(--color-primary);
}

.focus-card h4 {
  font-size: 1rem;
  font-weight: 600;
  color: var(--color-text);
  margin-bottom: 6px;
}

.focus-card p {
  font-size: 0.875rem;
  color: var(--color-text-secondary);
  line-height: 1.6;
}

/* ---- Call for Papers ---- */
.cfp-grid {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 48px;
  align-items: start;
}

.cfp-topics h3 {
  font-family: var(--font-serif);
  font-size: 1.4rem;
  font-weight: 600;
  margin-bottom: 8px;
  color: var(--color-text);
}

.cfp-topics > p {
  color: var(--color-text-secondary);
  margin-bottom: 20px;
  font-size: 0.95rem;
}

.topic-list {
  display: flex;
  flex-direction: column;
  gap: 10px;
}

.topic-list li {
  display: flex;
  align-items: flex-start;
  gap: 10px;
  color: var(--color-text-secondary);
  font-size: 0.9rem;
  line-height: 1.5;
  padding: 8px 12px;
  border-radius: var(--radius-sm);
  transition: background 0.2s;
}

.topic-list li:hover {
  background: rgba(26, 86, 219, 0.04);
}

.topic-list li::before {
  content: '';
  display: block;
  width: 6px;
  height: 6px;
  border-radius: 50%;
  background: var(--color-primary);
  margin-top: 7px;
  flex-shrink: 0;
}

.cfp-details {
  display: flex;
  flex-direction: column;
  gap: 24px;
}

.cfp-card {
  background: var(--color-bg);
  border: 1px solid var(--color-border);
  border-radius: var(--radius-lg);
  padding: 28px;
  box-shadow: var(--shadow-sm);
}

.cfp-card.cfp-highlight {
  background: linear-gradient(135deg, var(--color-primary-light), #eef4ff);
  border-color: rgba(26, 86, 219, 0.2);
}

.cfp-card h3 {
  font-family: var(--font-serif);
  font-size: 1.2rem;
  font-weight: 600;
  color: var(--color-text);
  margin-bottom: 16px;
}

.cfp-card p {
  color: var(--color-text-secondary);
  font-size: 0.9rem;
  line-height: 1.6;
  margin-bottom: 20px;
}

.guideline-list {
  display: flex;
  flex-direction: column;
  gap: 14px;
  margin-bottom: 24px;
}

.guideline-list li {
  font-size: 0.9rem;
  color: var(--color-text-secondary);
  line-height: 1.55;
  padding-left: 16px;
  border-left: 2px solid var(--color-primary-light);
}

.guideline-list li strong {
  color: var(--color-text);
}

.guideline-list li a {
  font-size: inherit;
}

/* ---- Dates Timeline ---- */
.dates-timeline {
  max-width: 640px;
  margin: 0 auto;
  position: relative;
}

.dates-timeline::before {
  content: '';
  position: absolute;
  left: 19px;
  top: 12px;
  bottom: 12px;
  width: 2px;
  background: var(--color-border);
}

.timeline-item {
  display: flex;
  align-items: center;
  gap: 24px;
  padding: 20px 0;
  position: relative;
}

.timeline-dot {
  width: 40px;
  height: 40px;
  border-radius: 50%;
  border: 3px solid var(--color-border);
  background: var(--color-bg);
  flex-shrink: 0;
  position: relative;
  z-index: 1;
  display: flex;
  align-items: center;
  justify-content: center;
}

.timeline-dot.upcoming {
  border-color: var(--color-primary);
  background: var(--color-primary-light);
}

.timeline-dot.upcoming::after {
  content: '';
  width: 12px;
  height: 12px;
  border-radius: 50%;
  background: var(--color-primary);
}

.timeline-dot.past {
  border-color: var(--color-secondary);
  background: #f0fdf9;
}

.timeline-dot.past::after {
  content: '✓';
  color: var(--color-secondary);
  font-size: 14px;
  font-weight: 700;
}

.timeline-content {
  flex: 1;
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding: 16px 20px;
  background: var(--color-bg);
  border: 1px solid var(--color-border);
  border-radius: var(--radius-md);
  box-shadow: var(--shadow-sm);
}

.timeline-label {
  font-weight: 600;
  font-size: 0.95rem;
  color: var(--color-text);
}

.timeline-date {
  font-size: 0.875rem;
  color: var(--color-text-muted);
  font-weight: 500;
}

.speaker-photo {
  display: block;
  width: 96px;
  height: 96px;
  border-radius: 50%;
  object-fit: cover;
  background: var(--color-primary-light);
  margin: 0 auto 16px;
  border: 3px solid var(--color-primary-light);
}

/* ---- Speakers ---- */
.speakers-grid {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(200px, 1fr));
  gap: 24px;
}

.speaker-card {
  text-align: center;
  padding: 28px 20px;
  background: var(--color-bg);
  border: 1px solid var(--color-border);
  border-radius: var(--radius-lg);
  box-shadow: var(--shadow-sm);
  transition: box-shadow 0.25s, transform 0.25s;
}

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

.speaker-avatar {
  width: 96px;
  height: 96px;
  border-radius: 50%;
  object-fit: cover;
  margin: 0 auto 16px;
  border: 3px solid var(--color-primary-light);
}

.speaker-name {
  font-weight: 600;
  font-size: 1rem;
  margin-bottom: 4px;
}

.speaker-affiliation {
  font-size: 0.8rem;
  color: var(--color-text-muted);
}

.speaker-tba {
  grid-column: 1 / -1;
  text-align: center;
  padding: 60px 24px;
  background: var(--color-bg);
  border: 2px dashed var(--color-border);
  border-radius: var(--radius-xl);
  color: var(--color-text-muted);
}

.tba-icon {
  width: 64px;
  height: 64px;
  border-radius: 50%;
  background: var(--color-primary-light);
  display: flex;
  align-items: center;
  justify-content: center;
  margin: 0 auto 16px;
}

.tba-icon svg {
  width: 32px;
  height: 32px;
  stroke: var(--color-primary);
}

.speaker-tba p {
  font-size: 0.95rem;
}

/* ---- Schedule ---- */
.schedule-table {
  border: 1px solid var(--color-border);
  border-radius: var(--radius-lg);
  overflow: hidden;
  box-shadow: var(--shadow-sm);
  background: var(--color-surface);
}

.schedule-head,
.schedule-row {
  display: grid;
  grid-template-columns: 170px minmax(200px, 1fr) minmax(220px, 1.4fr);
  gap: 20px;
  align-items: baseline;
  padding: 16px 24px;
}

.schedule-head {
  background: var(--color-bg-alt);
  border-bottom: 1px solid var(--color-border);
  font-size: 0.75rem;
  font-weight: 700;
  letter-spacing: 0.08em;
  text-transform: uppercase;
  color: var(--color-text-muted);
}

.schedule-row + .schedule-row,
.schedule-head + .schedule-row {
  border-top: 1px solid var(--color-border);
}

.schedule-row.is-break {
  background: var(--color-bg-alt);
}

.schedule-time {
  font-size: 0.875rem;
  font-weight: 600;
  color: var(--color-secondary);
  font-variant-numeric: tabular-nums;
  white-space: nowrap;
}

.schedule-session {
  font-weight: 600;
  font-size: 0.95rem;
  color: var(--color-text);
}

.schedule-row.is-talk .schedule-session {
  color: var(--color-primary);
}

.schedule-detail {
  font-size: 0.875rem;
  color: var(--color-text-secondary);
  line-height: 1.6;
}

/* ---- Organizers ---- */
.organizers-grid {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(240px, 1fr));
  gap: 24px;
}

.organizer-card {
  display: flex;
  align-items: center;
  gap: 16px;
  padding: 20px;
  background: var(--color-bg);
  border: 1px solid var(--color-border);
  border-radius: var(--radius-lg);
  box-shadow: var(--shadow-sm);
  transition: box-shadow 0.25s, transform 0.25s;
}

.organizer-card:hover {
  box-shadow: var(--shadow-md);
  transform: translateY(-2px);
}

.organizer-card.tba-card {
  grid-column: 1 / -1;
  justify-content: center;
  flex-direction: column;
  text-align: center;
  padding: 48px;
  border: 2px dashed var(--color-border);
}

.organizer-avatar {
  width: 64px;
  height: 64px;
  border-radius: 50%;
  object-fit: cover;
  flex-shrink: 0;
  border: 2px solid var(--color-primary-light);
}

.organizer-photo {
  width: 64px;
  height: 64px;
  border-radius: 50%;
  flex-shrink: 0;
  object-fit: cover;
  background: var(--color-primary-light);
  border: 2px solid var(--color-surface);
  box-shadow: 0 0 0 1px var(--color-border);
}

.organizer-info {
  min-width: 0;
}

.organizer-info h4 {
  font-size: 1rem;
  font-weight: 600;
  margin-bottom: 4px;
}

.organizer-info p {
  font-size: 0.8rem;
  color: var(--color-text-muted);
  overflow-wrap: break-word;
  word-break: break-word;
}

.organizer-info a {
  font-size: 0.8rem;
  display: block;
  margin-top: 4px;
  overflow-wrap: break-word;
  word-break: break-word;
}

.organizer-info .email-obfuscated {
  font-size: 0.8rem;
  display: block;
  margin-top: 4px;
  color: var(--color-primary);
  overflow-wrap: break-word;
  word-break: break-word;
}

/* ---- Footer ---- */
.footer {
  background: var(--color-hero-start);
  color: rgba(255,255,255,0.7);
  padding: 64px 0 32px;
}

.footer-grid {
  display: grid;
  grid-template-columns: 2fr 1fr 1fr;
  gap: 48px;
  margin-bottom: 48px;
}

.footer-brand h3 {
  font-family: var(--font-serif);
  color: #ffffff;
  font-size: 1.1rem;
  margin-bottom: 8px;
}

.footer-brand p {
  font-size: 0.875rem;
  line-height: 1.6;
  margin-bottom: 8px;
}

.footer-conference a {
  color: rgba(255,255,255,0.55);
  font-size: 0.8rem;
  transition: color 0.2s;
}

.footer-conference a:hover {
  color: rgba(255,255,255,0.9);
}

.footer-links h4 {
  color: #ffffff;
  font-size: 0.875rem;
  font-weight: 600;
  text-transform: uppercase;
  letter-spacing: 0.08em;
  margin-bottom: 16px;
}

.footer-links ul {
  display: flex;
  flex-direction: column;
  gap: 10px;
}

.footer-links a {
  color: rgba(255,255,255,0.6);
  font-size: 0.875rem;
  transition: color 0.2s;
}

.footer-links a:hover {
  color: rgba(255,255,255,0.95);
}

.footer-bottom {
  border-top: 1px solid rgba(255,255,255,0.1);
  padding-top: 24px;
  text-align: center;
}

.footer-bottom p {
  font-size: 0.8rem;
  color: rgba(255,255,255,0.4);
}

/* ---- Responsive ---- */
@media (max-width: 900px) {
  :root {
    --section-padding: 60px;
  }

  .overview-grid,
  .cfp-grid {
    grid-template-columns: 1fr;
    gap: 40px;
  }

  .footer-grid {
    grid-template-columns: 1fr 1fr;
  }

  .footer-brand {
    grid-column: 1 / -1;
  }
}

@media (max-width: 640px) {
  :root {
    --section-padding: 48px;
  }

  .nav-links {
    display: none;
    position: fixed;
    top: var(--nav-height);
    left: 0;
    right: 0;
    background: rgba(15, 23, 42, 0.98);
    flex-direction: column;
    padding: 16px;
    gap: 4px;
    border-bottom: 1px solid rgba(255,255,255,0.1);
  }

  .nav-links.open {
    display: flex;
  }

  .nav-links a {
    display: block;
    padding: 12px 16px;
    font-size: 0.95rem;
  }

  .nav-toggle {
    display: flex;
  }

  .hero-meta {
    gap: 20px;
  }

  .hero-actions {
    flex-direction: column;
    align-items: stretch;
  }

  .hero .btn-primary,
  .hero .btn-outline {
    text-align: center;
  }

  .timeline-content {
    flex-direction: column;
    align-items: flex-start;
    gap: 4px;
  }

  .schedule-head {
    display: none;
  }

  .schedule-row {
    grid-template-columns: 1fr;
    gap: 6px;
    padding: 16px 20px;
  }

  .footer-grid {
    grid-template-columns: 1fr;
  }

  .dates-timeline::before {
    left: 19px;
  }
}

/* ---- Animations ---- */
@media (prefers-reduced-motion: no-preference) {
  .section-header,
  .focus-card,
  .cfp-card,
  .timeline-item,
  .speaker-card,
  .organizer-card {
    opacity: 0;
    transform: translateY(20px);
    transition: opacity 0.5s ease, transform 0.5s ease;
  }

  .section-header.visible,
  .focus-card.visible,
  .cfp-card.visible,
  .timeline-item.visible,
  .speaker-card.visible,
  .organizer-card.visible {
    opacity: 1;
    transform: translateY(0);
  }

  .focus-card:nth-child(2) { transition-delay: 0.1s; }
  .focus-card:nth-child(3) { transition-delay: 0.2s; }
  .timeline-item:nth-child(2) { transition-delay: 0.1s; }
  .timeline-item:nth-child(3) { transition-delay: 0.2s; }
  .timeline-item:nth-child(4) { transition-delay: 0.3s; }
}