/* ============================================
   CSS Variables & Reset
   ============================================ */
:root {
  --primary: #003153;
  --primary-light: #004a7c;
  --primary-dark: #00213a;
  --accent: #f59e0b;
  --accent-light: #fbbf24;
  --bg: #fafaf8;
  --bg-alt: #f0efe8;
  --text: #2c2c2c;
  --text-light: #5a5a5a;
  --text-muted: #8a8a8a;
  --white: #ffffff;
  --shadow-sm: 0 2px 8px rgba(0,0,0,0.06);
  --shadow-md: 0 4px 20px rgba(0,0,0,0.08);
  --shadow-lg: 0 8px 40px rgba(0,0,0,0.1);
  --radius: 12px;
  --radius-sm: 8px;
  --transition: 0.3s ease;
}

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

html {
  scroll-behavior: smooth;
  scroll-padding-top: 80px;
}

body {
  font-family: 'Inter', -apple-system, BlinkMacSystemFont, sans-serif;
  color: var(--text);
  background: var(--bg);
  line-height: 1.7;
  -webkit-font-smoothing: antialiased;
}

/* ============================================
   Navigation
   ============================================ */
.navbar {
  position: fixed;
  top: 0;
  left: 0;
  right: 0;
  z-index: 1000;
  background: rgba(255,255,255,0.92);
  backdrop-filter: blur(12px);
  border-bottom: 1px solid rgba(0,0,0,0.06);
  transition: var(--transition);
}

.navbar.scrolled {
  box-shadow: var(--shadow-sm);
}

.nav-container {
  max-width: 1100px;
  margin: 0 auto;
  padding: 0 24px;
  display: flex;
  align-items: center;
  justify-content: space-between;
  height: 68px;
}

.nav-logo {
  font-family: 'Playfair Display', serif;
  font-size: 1.2rem;
  font-weight: 700;
  color: var(--primary);
  text-decoration: none;
  letter-spacing: -0.5px;
  display: flex;
  align-items: center;
  gap: 10px;
}

.nav-photo {
  width: 34px;
  height: 34px;
  border-radius: 50%;
  object-fit: cover;
  object-position: center top;
  border: 2px solid var(--primary);
}

.nav-links {
  display: flex;
  list-style: none;
  gap: 32px;
}

.nav-links a {
  text-decoration: none;
  color: var(--text-light);
  font-size: 0.9rem;
  font-weight: 500;
  transition: var(--transition);
  position: relative;
}

.nav-links a::after {
  content: '';
  position: absolute;
  bottom: -4px;
  left: 0;
  width: 0;
  height: 2px;
  background: var(--primary);
  transition: var(--transition);
}

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

.nav-links a:hover::after {
  width: 100%;
}

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

.nav-toggle span {
  display: block;
  width: 24px;
  height: 2px;
  background: var(--text);
  transition: var(--transition);
}

/* ============================================
   Hero Section
   ============================================ */
.hero {
  min-height: 100vh;
  display: flex;
  flex-direction: column;
  justify-content: center;
  align-items: center;
  padding: 120px 24px 60px;
  position: relative;
  background: linear-gradient(165deg, var(--bg) 0%, #e0e8f0 50%, var(--bg-alt) 100%);
}

.hero-content {
  max-width: 1100px;
  width: 100%;
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 60px;
}

.hero-text {
  flex: 1;
}

.hero-greeting {
  font-size: 1rem;
  font-weight: 500;
  color: var(--primary);
  letter-spacing: 2px;
  text-transform: uppercase;
  margin-bottom: 8px;
}

.hero-name {
  font-family: 'Playfair Display', serif;
  font-size: 3.5rem;
  font-weight: 700;
  color: var(--text);
  line-height: 1.15;
  margin-bottom: 12px;
  letter-spacing: -1px;
}

.hero-headline {
  font-size: 1.25rem;
  color: var(--primary-light);
  font-weight: 500;
  margin-bottom: 10px;
}

.hero-subheadline {
  font-size: 0.95rem;
  color: var(--text-light);
  line-height: 1.6;
  margin-bottom: 20px;
  max-width: 500px;
  text-align: justify;
}

.hero-bio {
  font-size: 1.05rem;
  color: var(--text-light);
  max-width: 520px;
  margin-bottom: 32px;
  line-height: 1.8;
}

.hero-actions {
  display: flex;
  gap: 16px;
  flex-wrap: wrap;
}

.btn {
  display: inline-block;
  padding: 14px 32px;
  border-radius: 50px;
  font-size: 0.95rem;
  font-weight: 600;
  text-decoration: none;
  transition: var(--transition);
  cursor: pointer;
}

.btn-primary {
  background: var(--primary);
  color: var(--white);
  border: 2px solid var(--primary);
}

.btn-primary:hover {
  background: var(--primary-dark);
  border-color: var(--primary-dark);
  transform: translateY(-2px);
  box-shadow: var(--shadow-md);
}

.btn-outline {
  background: transparent;
  color: var(--primary);
  border: 2px solid var(--primary);
}

.btn-outline:hover {
  background: var(--primary);
  color: var(--white);
  transform: translateY(-2px);
}

.hero-visual {
  flex-shrink: 0;
}

.hero-avatar {
  width: 260px;
  height: 300px;
  border-radius: 140px;
  background: linear-gradient(135deg, var(--primary), var(--primary-light));
  display: flex;
  align-items: center;
  justify-content: center;
  box-shadow: 0 20px 60px rgba(0, 49, 83, 0.25);
  overflow: hidden;
}

.hero-avatar img {
  width: 100%;
  height: 100%;
  object-fit: cover;
  object-position: center top;
}

.hero-avatar span {
  font-family: 'Playfair Display', serif;
  font-size: 5rem;
  font-weight: 700;
  color: rgba(255,255,255,0.9);
}

.scroll-indicator {
  position: absolute;
  bottom: 32px;
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: 8px;
  animation: bounce 2s infinite;
}

.scroll-indicator span {
  font-size: 0.75rem;
  color: var(--text-muted);
  text-transform: uppercase;
  letter-spacing: 2px;
}

.scroll-arrow {
  width: 20px;
  height: 20px;
  border-right: 2px solid var(--text-muted);
  border-bottom: 2px solid var(--text-muted);
  transform: rotate(45deg);
}

@keyframes bounce {
  0%, 100% { transform: translateY(0); }
  50% { transform: translateY(8px); }
}

/* ============================================
   Sections
   ============================================ */
.section {
  padding: 100px 24px;
}

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

.container {
  max-width: 900px;
  margin: 0 auto;
}

.section-title {
  font-family: 'Playfair Display', serif;
  font-size: 2.2rem;
  font-weight: 700;
  color: var(--text);
  margin-bottom: 48px;
  position: relative;
  display: inline-block;
}

.section-title::after {
  content: '';
  position: absolute;
  bottom: -8px;
  left: 0;
  width: 50px;
  height: 3px;
  background: var(--accent);
  border-radius: 2px;
}

/* ============================================
   About
   ============================================ */
.about-content p {
  font-size: 1.05rem;
  color: var(--text-light);
  line-height: 1.9;
  margin-bottom: 32px;
  text-align: justify;
}

.about-interests {
  background: var(--bg-alt);
  border: 1px solid rgba(0, 49, 83, 0.1);
  border-radius: var(--radius);
  padding: 28px 28px 20px;
  margin-top: 8px;
}

.about-interests h3 {
  font-family: 'Playfair Display', serif;
  font-size: 1.15rem;
  font-weight: 700;
  margin-bottom: 18px;
  color: var(--text);
}

.interests-grid {
  display: grid;
  grid-template-columns: repeat(5, 1fr);
  gap: 12px;
}

.interest-card {
  display: flex;
  flex-direction: column;
  align-items: center;
  text-align: center;
  gap: 8px;
  padding: 14px 6px;
  border-radius: var(--radius-sm);
  transition: var(--transition);
  cursor: default;
}

.interest-card:hover {
  background: rgba(0, 49, 83, 0.06);
}

.interest-card:hover .interest-icon {
  transform: translateY(-3px);
}

.interest-icon {
  width: 48px;
  height: 48px;
  transition: var(--transition);
  display: flex;
  align-items: center;
  justify-content: center;
}

.interest-icon i,
.interest-icon svg {
  font-size: 2.2rem;
  width: 100%;
  height: 100%;
}

.interest-card span {
  font-size: 0.78rem;
  font-weight: 500;
  color: var(--text-light);
  line-height: 1.3;
}

/* ============================================
   Education Timeline
   ============================================ */
.timeline {
  position: relative;
  padding-left: 40px;
}

.timeline::before {
  content: '';
  position: absolute;
  left: 8px;
  top: 4px;
  bottom: 0;
  width: 2px;
  background: #d4d4d0;
}

.timeline-item {
  position: relative;
  margin-bottom: 36px;
}

.timeline-item:last-child {
  margin-bottom: 0;
}

.timeline-marker {
  position: absolute;
  left: -36px;
  top: 6px;
  width: 14px;
  height: 14px;
  border-radius: 50%;
  background: var(--white);
  border: 3px solid var(--primary);
  z-index: 1;
  transition: all 0.4s ease;
}

.timeline-item.active .timeline-marker {
  background: var(--primary);
  box-shadow: 0 0 0 6px rgba(0, 49, 83, 0.18);
  transform: scale(1.3);
}

.timeline-item.passed .timeline-marker {
  background: var(--primary);
  box-shadow: 0 0 0 4px rgba(0, 49, 83, 0.1);
}

.timeline-progress {
  position: absolute;
  left: 8px;
  top: 4px;
  width: 2px;
  height: 0;
  background: var(--primary);
  z-index: 1;
  transition: height 0.3s ease;
}


.timeline-content {
  background: var(--white);
  padding: 24px 28px;
  border-radius: var(--radius);
  box-shadow: var(--shadow-sm);
  transition: var(--transition);
}

.timeline-content:hover {
  box-shadow: var(--shadow-md);
  transform: translateX(4px);
}

.timeline-year {
  display: inline-block;
  font-size: 0.8rem;
  font-weight: 600;
  color: var(--primary);
  background: rgba(0, 49, 83, 0.08);
  padding: 4px 12px;
  border-radius: 50px;
  margin-bottom: 10px;
}

.timeline-content h3 {
  font-size: 1.05rem;
  font-weight: 600;
  margin-bottom: 4px;
  color: var(--text);
}

.timeline-institution {
  font-size: 0.9rem;
  color: var(--text-light);
  margin-bottom: 4px;
}

.timeline-grade {
  font-size: 0.85rem;
  color: var(--text-muted);
  font-weight: 500;
}

/* ============================================
   Experience
   ============================================ */
.experience-card {
  background: var(--white);
  border-radius: var(--radius);
  padding: 32px;
  box-shadow: var(--shadow-sm);
  border-left: 4px solid var(--primary);
}

.experience-header {
  display: flex;
  justify-content: space-between;
  align-items: flex-start;
  margin-bottom: 20px;
  flex-wrap: wrap;
  gap: 12px;
}

.experience-header h3 {
  font-size: 1.15rem;
  font-weight: 600;
  color: var(--text);
}

.experience-company {
  font-size: 0.95rem;
  color: var(--primary-light);
  font-weight: 500;
  margin-top: 4px;
}

.experience-period {
  font-size: 0.8rem;
  font-weight: 600;
  color: var(--accent);
  background: rgba(212, 168, 67, 0.1);
  padding: 6px 16px;
  border-radius: 50px;
  white-space: nowrap;
}

.experience-responsibilities {
  list-style: none;
  display: flex;
  flex-direction: column;
  gap: 10px;
}

.experience-responsibilities li {
  position: relative;
  padding-left: 20px;
  font-size: 0.92rem;
  color: var(--text-light);
  line-height: 1.6;
  text-align: justify;
}

.experience-responsibilities li::before {
  content: '';
  position: absolute;
  left: 0;
  top: 10px;
  width: 6px;
  height: 6px;
  border-radius: 50%;
  background: var(--primary);
}

/* ============================================
   Skills
   ============================================ */
.skills-container {
  background: var(--bg-alt);
  border: 1px solid rgba(0, 49, 83, 0.1);
  border-radius: var(--radius);
  padding: 28px 28px 20px;
}

.skills-container h3 {
  font-family: 'Playfair Display', serif;
  font-size: 1.15rem;
  font-weight: 700;
  margin-bottom: 18px;
  color: var(--text);
}

.skills-grid {
  display: grid;
  grid-template-columns: repeat(6, 1fr);
  gap: 12px;
}

.skill-card {
  display: flex;
  flex-direction: column;
  align-items: center;
  text-align: center;
  gap: 8px;
  padding: 14px 6px;
  border-radius: var(--radius-sm);
  transition: var(--transition);
  cursor: default;
}

.skill-card:hover {
  background: rgba(0, 49, 83, 0.06);
}

.skill-card:hover .skill-icon {
  transform: translateY(-3px);
}

.skill-icon {
  width: 48px;
  height: 48px;
  transition: var(--transition);
  display: flex;
  align-items: center;
  justify-content: center;
}

.skill-icon i {
  font-size: 2.2rem;
}

.skill-card span {
  font-size: 0.78rem;
  font-weight: 500;
  color: var(--text-light);
  line-height: 1.3;
}

/* ============================================
   Research
   ============================================ */
.research-subsection {
  margin-bottom: 48px;
}

.research-subsection:last-child {
  margin-bottom: 0;
}

.research-subtitle {
  font-family: 'Playfair Display', serif;
  font-size: 1.4rem;
  font-weight: 600;
  color: var(--text);
  margin-bottom: 24px;
  padding-bottom: 12px;
  border-bottom: 2px solid rgba(0, 49, 83, 0.1);
}

.research-card {
  background: var(--white);
  border-radius: var(--radius);
  padding: 28px 32px;
  box-shadow: var(--shadow-sm);
  margin-bottom: 16px;
  transition: var(--transition);
}

.research-card:hover {
  box-shadow: var(--shadow-md);
}

.publication-card {
  display: flex;
  align-items: flex-start;
  gap: 24px;
  border-left: 4px solid var(--accent);
}

.research-number {
  font-family: 'Playfair Display', serif;
  font-size: 2rem;
  font-weight: 700;
  color: var(--accent);
  line-height: 1;
  flex-shrink: 0;
}

.research-body h4 {
  font-size: 1.05rem;
  font-weight: 600;
  color: var(--text);
  line-height: 1.5;
  margin-bottom: 10px;
}

.research-type-badge {
  display: inline-block;
  font-size: 0.75rem;
  font-weight: 600;
  padding: 4px 14px;
  border-radius: 50px;
  text-transform: uppercase;
  letter-spacing: 0.5px;
}

.publication-badge {
  background: rgba(212, 168, 67, 0.12);
  color: var(--accent);
}

.thesis-badge {
  background: rgba(0, 49, 83, 0.08);
  color: var(--primary);
}

.thesis-card {
  border-left: 4px solid var(--primary);
}

.thesis-abstract {
  margin-top: 16px;
}

.abstract-toggle {
  background: none;
  border: 1px solid rgba(0, 49, 83, 0.2);
  color: var(--primary);
  padding: 8px 20px;
  border-radius: 50px;
  font-size: 0.85rem;
  font-weight: 500;
  cursor: pointer;
  transition: var(--transition);
}

.abstract-toggle:hover {
  background: var(--primary);
  color: var(--white);
  border-color: var(--primary);
}

.abstract-content {
  margin-top: 16px;
  padding: 20px;
  background: var(--bg);
  border-radius: var(--radius-sm);
  display: none;
}

.abstract-content.visible {
  display: block;
}

.abstract-content p {
  font-size: 0.9rem;
  color: var(--text-light);
  line-height: 1.8;
  text-align: justify;
}

.thesis-keywords {
  display: flex;
  flex-wrap: wrap;
  gap: 8px;
  margin-top: 16px;
}

.keyword {
  font-size: 0.78rem;
  padding: 5px 14px;
  background: rgba(0, 49, 83, 0.06);
  color: var(--primary);
  border-radius: 50px;
  font-weight: 500;
}

/* ============================================
   Achievements
   ============================================ */
.achievement-card {
  display: flex;
  align-items: flex-start;
  gap: 20px;
  background: var(--white);
  padding: 28px 32px;
  border-radius: var(--radius);
  box-shadow: var(--shadow-sm);
}

.achievement-icon {
  font-size: 2rem;
  color: var(--accent);
  flex-shrink: 0;
}

.achievement-card h3 {
  font-size: 1.05rem;
  font-weight: 600;
  color: var(--text);
  margin-bottom: 6px;
}

.achievement-card p {
  font-size: 0.92rem;
  color: var(--text-light);
  text-align: justify;
}

/* ============================================
   Contact
   ============================================ */
.contact-grid {
  display: flex;
  justify-content: center;
  gap: 20px;
  flex-wrap: wrap;
}

.contact-card.icon-only {
  background: var(--white);
  padding: 18px 22px;
  border-radius: var(--radius);
  text-align: center;
  text-decoration: none;
  color: var(--text);
  box-shadow: var(--shadow-sm);
  transition: var(--transition);
  border: 1px solid transparent;
  min-width: 90px;
}

.contact-card.icon-only:hover {
  box-shadow: var(--shadow-md);
  transform: translateY(-4px);
  border-color: var(--primary);
}

.contact-icon {
  font-size: 2rem;
  margin-bottom: 6px;
  font-weight: 700;
}

.contact-brand-img {
  width: 1em;
  height: 1em;
  object-fit: contain;
}

.contact-card h3 {
  font-size: 0.75rem;
  font-weight: 600;
  color: var(--text-light);
  margin: 0;
}

/* ============================================
   Back to Top
   ============================================ */
.back-to-top {
  position: fixed;
  bottom: 30px;
  right: 30px;
  width: 44px;
  height: 44px;
  border-radius: 50%;
  background: var(--primary);
  color: var(--white);
  border: none;
  font-size: 1.3rem;
  cursor: pointer;
  opacity: 0;
  visibility: hidden;
  transition: var(--transition);
  box-shadow: var(--shadow-md);
  z-index: 999;
}

.back-to-top.visible {
  opacity: 1;
  visibility: visible;
}

.back-to-top:hover {
  background: var(--primary-dark);
  transform: translateY(-3px);
}

/* ============================================
   Brand Colors
   ============================================ */
/* Skills */
.brand-microsoft { color: #D83B01; }
.brand-origin { color: #0C4DA2; }
.brand-minitab { color: #00843D; }
.brand-spss { color: #CC0000; }
.brand-powerbi { color: #D4A017; }
.brand-python { color: #3776AB; }

/* Key Interests */
.color-fiber { color: #8B5E3C; }
.color-smart { color: #1E88E5; }
.color-circular { color: #43A047; }
.color-biomedical { color: #E53935; }
.color-composites { color: #F57C00; }
.color-biopolymers { color: #8E24AA; }
.color-eco { color: #2E7D32; }
.color-geo { color: #0277BD; }
.color-nano { color: #00ACC1; }
.color-process { color: #546E7A; }

/* Contact */
.brand-gmail { color: #EA4335; }
.brand-phone { color: #25D366; }
.brand-linkedin { color: #0A66C2; }
.brand-orcid { color: #A6CE39; }
.brand-scholar { color: #4285F4; }
.brand-facebook { color: #1877F2; }

/* ============================================
   Footer
   ============================================ */
.footer {
  background: var(--primary-dark);
  color: rgba(255,255,255,0.7);
  text-align: center;
  padding: 28px 24px;
  font-size: 0.85rem;
}

/* ============================================
   Animations
   ============================================ */
.fade-in {
  opacity: 0;
  transform: translateY(24px);
  transition: opacity 0.6s ease, transform 0.6s ease;
}

.fade-in.visible {
  opacity: 1;
  transform: translateY(0);
}

/* ============================================
   Responsive
   ============================================ */
@media (max-width: 768px) {
  .nav-toggle {
    display: flex;
  }

  .nav-links {
    display: none;
    position: absolute;
    top: 68px;
    left: 0;
    right: 0;
    background: var(--white);
    flex-direction: column;
    padding: 20px 24px;
    gap: 16px;
    box-shadow: var(--shadow-md);
    border-top: 1px solid rgba(0,0,0,0.06);
  }

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

  .hero-content {
    flex-direction: column-reverse;
    text-align: center;
    gap: 40px;
  }

  .hero-bio {
    margin-left: auto;
    margin-right: auto;
  }

  .hero-actions {
    justify-content: center;
  }

  .hero-name {
    font-size: 2.4rem;
  }

  .hero-avatar {
    width: 180px;
    height: 180px;
  }

  .hero-avatar span {
    font-size: 3.5rem;
  }

  .section {
    padding: 70px 20px;
  }

  .section-title {
    font-size: 1.8rem;
  }

  .experience-header {
    flex-direction: column;
  }

  .publication-card {
    flex-direction: column;
    gap: 12px;
  }

  .skills-grid {
    grid-template-columns: repeat(3, 1fr);
    gap: 10px;
  }

  .interests-grid {
    grid-template-columns: repeat(3, 1fr);
    gap: 10px;
  }

  .contact-grid {
    gap: 12px;
  }
  .contact-card.icon-only {
    min-width: 70px;
    padding: 14px 16px;
  }
}

@media (max-width: 480px) {
  .skills-grid {
    grid-template-columns: repeat(2, 1fr);
    gap: 8px;
  }

  .interests-grid {
    grid-template-columns: repeat(2, 1fr);
    gap: 8px;
  }

  .about-interests {
    padding: 20px 16px 14px;
  }
  .hero-name {
    font-size: 2rem;
  }

  .btn {
    padding: 12px 24px;
    font-size: 0.9rem;
  }

  .timeline {
    padding-left: 30px;
  }

  .timeline-content {
    padding: 18px 20px;
  }
}