/* ============================================
   Variables & Reset
   ============================================ */
:root {
  --color-bg: #fafafa;
  --color-bg-alt: #f0f2f5;
  --color-surface: #ffffff;
  --color-text: #1a1a2e;
  --color-text-secondary: #555770;
  --color-accent: #4361ee;
  --color-accent-light: #e8ecff;
  --color-accent-dark: #3249d4;
  --color-border: #e2e4ea;
  --color-award: #e8a838;
  --font-sans: 'Inter', 'Noto Sans JP', -apple-system, BlinkMacSystemFont, sans-serif;
  --radius: 12px;
  --radius-sm: 8px;
  --shadow-sm: 0 1px 3px rgba(0,0,0,0.06);
  --shadow-md: 0 4px 16px rgba(0,0,0,0.08);
  --shadow-lg: 0 8px 32px rgba(0,0,0,0.10);
  --transition: 0.3s cubic-bezier(0.4, 0, 0.2, 1);
  --max-width: 860px;
}

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

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

body {
  font-family: var(--font-sans);
  background: var(--color-bg);
  color: var(--color-text);
  line-height: 1.7;
  font-size: 15px;
  -webkit-font-smoothing: antialiased;
}

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

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

img {
  max-width: 100%;
}

/* ============================================
   Layout
   ============================================ */
.container {
  max-width: var(--max-width);
  margin: 0 auto;
  padding: 0 1.5rem;
}

.section {
  padding: 4rem 0;
}

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

/* ============================================
   Navigation
   ============================================ */
.nav {
  position: fixed;
  top: 0;
  left: 0;
  right: 0;
  z-index: 100;
  background: transparent;
  transition: background var(--transition), box-shadow var(--transition);
}

.nav.scrolled {
  background: rgba(255, 255, 255, 0.92);
  backdrop-filter: blur(12px);
  -webkit-backdrop-filter: blur(12px);
  box-shadow: var(--shadow-sm);
}

.nav-inner {
  max-width: var(--max-width);
  margin: 0 auto;
  padding: 0 1.5rem;
  display: flex;
  align-items: center;
  justify-content: space-between;
  height: 64px;
}

.nav-logo {
  font-weight: 700;
  font-size: 1.05rem;
  color: var(--color-text);
  letter-spacing: -0.02em;
}

.nav.scrolled .nav-logo {
  color: var(--color-text);
}

.nav:not(.scrolled) .nav-logo {
  color: #fff;
}

.nav-links {
  display: flex;
  gap: 1.5rem;
  list-style: none;
}

.nav-links a {
  font-size: 0.875rem;
  font-weight: 500;
  color: var(--color-text-secondary);
  transition: color var(--transition);
}

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

.nav:not(.scrolled) .nav-links a {
  color: rgba(255, 255, 255, 0.8);
}

.nav:not(.scrolled) .nav-links a:hover {
  color: #fff;
}

/* Hamburger */
.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: var(--color-text);
  border-radius: 2px;
  transition: transform var(--transition), opacity var(--transition);
}

.nav:not(.scrolled) .nav-toggle span {
  background: #fff;
}

.nav-toggle.open span:nth-child(1) {
  transform: translateY(7px) rotate(45deg);
}
.nav-toggle.open span:nth-child(2) {
  opacity: 0;
}
.nav-toggle.open span:nth-child(3) {
  transform: translateY(-7px) rotate(-45deg);
}

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

  .nav-links {
    position: fixed;
    top: 64px;
    left: 0;
    right: 0;
    background: rgba(255, 255, 255, 0.97);
    backdrop-filter: blur(12px);
    flex-direction: column;
    padding: 1.5rem;
    gap: 1rem;
    box-shadow: var(--shadow-md);
    transform: translateY(-120%);
    transition: transform var(--transition);
  }

  .nav-links.open {
    transform: translateY(0);
  }

  .nav-links a {
    color: var(--color-text) !important;
    font-size: 1rem;
  }
}

/* ============================================
   Hero
   ============================================ */
.hero {
  position: relative;
  min-height: 100vh;
  display: flex;
  align-items: center;
  overflow: hidden;
}

.hero-bg {
  position: absolute;
  inset: 0;
  background: linear-gradient(135deg, #1a1a2e 0%, #16213e 40%, #0f3460 70%, #4361ee 100%);
  z-index: -1;
}

.hero-bg::after {
  content: '';
  position: absolute;
  inset: 0;
  background:
    radial-gradient(ellipse at 20% 50%, rgba(67, 97, 238, 0.15) 0%, transparent 60%),
    radial-gradient(ellipse at 80% 20%, rgba(67, 97, 238, 0.1) 0%, transparent 50%);
}

.hero-content {
  text-align: center;
  color: #fff;
  padding-top: 80px;
  padding-bottom: 60px;
}

.hero-greeting {
  font-size: 0.95rem;
  font-weight: 400;
  letter-spacing: 0.15em;
  text-transform: uppercase;
  opacity: 0.7;
  margin-bottom: 0.75rem;
}

.hero-name {
  font-size: clamp(2.2rem, 5vw, 3.5rem);
  font-weight: 700;
  letter-spacing: -0.03em;
  line-height: 1.2;
  margin-bottom: 0.5rem;
}

.hero-name-jp {
  display: block;
  font-size: 0.5em;
  font-weight: 400;
  opacity: 0.6;
  margin-top: 0.25rem;
  letter-spacing: 0.1em;
}

.hero-title {
  font-size: 1.1rem;
  font-weight: 400;
  opacity: 0.75;
  margin-bottom: 1.5rem;
  letter-spacing: 0.02em;
}

.hero-affiliation {
  font-size: 0.95rem;
  opacity: 0.7;
  line-height: 1.8;
  margin-bottom: 1.5rem;
}

.hero-affiliation a {
  color: rgba(255, 255, 255, 0.9);
  border-bottom: 1px solid rgba(255, 255, 255, 0.3);
}

.hero-affiliation a:hover {
  color: #fff;
  border-bottom-color: #fff;
}

.hero-contact {
  display: flex;
  flex-wrap: wrap;
  justify-content: center;
  gap: 0.75rem 1.5rem;
  margin-bottom: 2rem;
}

.contact-item {
  font-size: 0.85rem;
  opacity: 0.6;
  font-family: monospace;
}

.hero-social {
  display: flex;
  justify-content: center;
  gap: 1rem;
}

.hero-social a {
  display: flex;
  align-items: center;
  justify-content: center;
  width: 44px;
  height: 44px;
  border-radius: 50%;
  background: rgba(255, 255, 255, 0.1);
  color: rgba(255, 255, 255, 0.8);
  transition: background var(--transition), color var(--transition), transform var(--transition);
}

.hero-social a:hover {
  background: rgba(255, 255, 255, 0.2);
  color: #fff;
  transform: translateY(-2px);
}

/* ============================================
   Section Titles
   ============================================ */
.section-title {
  font-size: 1.6rem;
  font-weight: 700;
  letter-spacing: -0.02em;
  margin-bottom: 2rem;
  position: relative;
  padding-bottom: 0.75rem;
}

.section-title::after {
  content: '';
  position: absolute;
  bottom: 0;
  left: 0;
  width: 40px;
  height: 3px;
  background: var(--color-accent);
  border-radius: 2px;
}

.subsection-title {
  font-size: 1.1rem;
  font-weight: 600;
  color: var(--color-text-secondary);
  margin-bottom: 1.25rem;
  margin-top: 2.5rem;
}

.subsection-title:first-child {
  margin-top: 0;
}

/* ============================================
   Cards
   ============================================ */
.card {
  background: var(--color-surface);
  border-radius: var(--radius);
  padding: 2rem;
  box-shadow: var(--shadow-sm);
  border: 1px solid var(--color-border);
}

.card-accent {
  border-left: 4px solid var(--color-accent);
}

.research-text {
  font-size: 0.95rem;
  color: var(--color-text-secondary);
  line-height: 1.9;
}

.research-text strong {
  color: var(--color-text);
  font-weight: 600;
}

/* ============================================
   Timeline
   ============================================ */
.timeline {
  position: relative;
  padding-left: 2rem;
}

.timeline::before {
  content: '';
  position: absolute;
  left: 7px;
  top: 4px;
  bottom: 4px;
  width: 2px;
  background: var(--color-border);
}

.timeline-item {
  position: relative;
  padding-bottom: 2rem;
}

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

.timeline-marker {
  position: absolute;
  left: -2rem;
  top: 4px;
  width: 16px;
  height: 16px;
  border-radius: 50%;
  background: var(--color-surface);
  border: 3px solid var(--color-accent);
  z-index: 1;
}

.timeline-content h3 {
  font-size: 1.05rem;
  font-weight: 600;
  margin-bottom: 0.25rem;
}

.timeline-content p {
  font-size: 0.9rem;
  color: var(--color-text-secondary);
}

.timeline-date {
  display: inline-block;
  font-size: 0.8rem;
  font-weight: 500;
  color: var(--color-accent);
  background: var(--color-accent-light);
  padding: 0.15rem 0.6rem;
  border-radius: 4px;
  margin-bottom: 0.5rem;
}

.link-inline {
  font-size: 0.875rem;
  font-weight: 500;
}

/* ============================================
   Publications
   ============================================ */
.pub-list {
  display: flex;
  flex-direction: column;
  gap: 0;
}

.pub-item {
  display: flex;
  gap: 1.25rem;
  padding: 1.25rem 0;
  border-bottom: 1px solid var(--color-border);
}

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

.pub-date {
  flex-shrink: 0;
  font-size: 0.8rem;
  font-weight: 600;
  color: var(--color-text-secondary);
  width: 60px;
  padding-top: 2px;
  font-variant-numeric: tabular-nums;
}

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

a.pub-title {
  font-size: 0.95rem;
  font-weight: 600;
  color: var(--color-text);
  line-height: 1.5;
  display: block;
  margin-bottom: 0.25rem;
}

a.pub-title:hover {
  color: var(--color-accent);
}

span.pub-title {
  font-size: 0.95rem;
  font-weight: 600;
  color: var(--color-text);
  line-height: 1.5;
  display: block;
  margin-bottom: 0.25rem;
}

.pub-venue {
  font-size: 0.85rem;
  color: var(--color-text-secondary);
  margin-bottom: 0.15rem;
}

.pub-venue a {
  color: var(--color-text-secondary);
  text-decoration: underline;
  text-underline-offset: 2px;
}

.pub-venue a:hover {
  color: var(--color-accent);
}

.pub-authors {
  font-size: 0.82rem;
  color: var(--color-text-secondary);
  margin-bottom: 0.5rem;
}

.pub-authors u {
  text-decoration: underline;
  text-underline-offset: 2px;
  font-weight: 500;
  color: var(--color-text);
}

.pub-tag {
  display: inline-block;
  font-size: 0.7rem;
  font-weight: 600;
  text-transform: uppercase;
  letter-spacing: 0.05em;
  padding: 0.15rem 0.5rem;
  border-radius: 4px;
  background: var(--color-bg-alt);
  color: var(--color-text-secondary);
  margin-right: 0.35rem;
}

.pub-award {
  display: inline-block;
  font-size: 0.7rem;
  font-weight: 600;
  letter-spacing: 0.03em;
  padding: 0.15rem 0.55rem;
  border-radius: 4px;
  background: #fff7e6;
  color: var(--color-award);
  border: 1px solid #fce4b0;
}

/* ============================================
   Awards
   ============================================ */
.awards-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(280px, 1fr));
  gap: 1rem;
}

.award-card {
  background: var(--color-surface);
  border-radius: var(--radius-sm);
  padding: 1.25rem 1.5rem;
  border: 1px solid var(--color-border);
  display: flex;
  align-items: flex-start;
  gap: 0.75rem;
}

.award-icon {
  font-size: 1.5rem;
  flex-shrink: 0;
}

.award-card p {
  font-size: 0.9rem;
  color: var(--color-text-secondary);
}

/* ============================================
   Activities
   ============================================ */
.activities-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(300px, 1fr));
  gap: 2rem;
}

.activity-group {
  background: var(--color-surface);
  border-radius: var(--radius);
  padding: 1.5rem;
  border: 1px solid var(--color-border);
}

.activity-group .subsection-title {
  margin-top: 0;
  margin-bottom: 1rem;
}

.activity-list {
  list-style: none;
  display: flex;
  flex-direction: column;
  gap: 0.75rem;
}

.activity-list li {
  font-size: 0.9rem;
  padding-left: 1rem;
  position: relative;
}

.activity-list li::before {
  content: '';
  position: absolute;
  left: 0;
  top: 0.55em;
  width: 5px;
  height: 5px;
  border-radius: 50%;
  background: var(--color-accent);
}

.activity-meta {
  display: block;
  font-size: 0.8rem;
  color: var(--color-text-secondary);
  margin-top: 0.1rem;
}

/* ============================================
   Skills
   ============================================ */
.skills-row {
  display: flex;
  flex-wrap: wrap;
  gap: 0.5rem;
}

.skill-chip {
  font-size: 0.85rem;
  font-weight: 500;
  padding: 0.4rem 1rem;
  border-radius: 100px;
  background: var(--color-accent-light);
  color: var(--color-accent);
  border: 1px solid transparent;
  transition: background var(--transition), border-color var(--transition);
}

.skill-chip:hover {
  border-color: var(--color-accent);
}

/* ============================================
   Link Cards
   ============================================ */
.link-cards {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(180px, 1fr));
  gap: 1rem;
}

.link-card {
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: 0.75rem;
  padding: 1.5rem 1rem;
  background: var(--color-surface);
  border-radius: var(--radius);
  border: 1px solid var(--color-border);
  color: var(--color-text);
  transition: transform var(--transition), box-shadow var(--transition), border-color var(--transition);
}

.link-card:hover {
  transform: translateY(-4px);
  box-shadow: var(--shadow-md);
  border-color: var(--color-accent);
  color: var(--color-accent);
}

.link-card span {
  font-size: 0.9rem;
  font-weight: 500;
}

/* ============================================
   Footer
   ============================================ */
.footer {
  padding: 2rem 0;
  text-align: center;
  border-top: 1px solid var(--color-border);
}

.footer p {
  font-size: 0.8rem;
  color: var(--color-text-secondary);
}

/* ============================================
   Animations
   ============================================ */
.fade-in {
  opacity: 0;
  transform: translateY(20px);
  transition: opacity 0.6s ease, transform 0.6s ease;
}

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

/* ============================================
   Responsive
   ============================================ */
/* Products */
.products-grid {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: 1.5rem;
}

.product-card {
  background: var(--color-surface);
  border-radius: var(--radius);
  overflow: hidden;
  box-shadow: var(--shadow-sm);
  transition: transform 0.2s, box-shadow 0.2s;
  cursor: pointer;
}

.product-card:hover {
  transform: translateY(-4px);
  box-shadow: var(--shadow-md);
}

.product-thumb {
  width: 100%;
  height: 160px;
  object-fit: cover;
  display: block;
}

.product-card h3 {
  font-size: 0.95rem;
  font-weight: 600;
  padding: 0.75rem 1rem;
  color: var(--color-text);
  line-height: 1.4;
}

/* Modal */
.modal-overlay {
  position: fixed;
  inset: 0;
  background: rgba(0, 0, 0, 0.6);
  backdrop-filter: blur(4px);
  display: flex;
  align-items: center;
  justify-content: center;
  z-index: 1000;
  opacity: 0;
  pointer-events: none;
  transition: opacity 0.25s;
  padding: 1.5rem;
}

.modal-overlay.active {
  opacity: 1;
  pointer-events: auto;
}

.modal-content {
  background: var(--color-surface);
  border-radius: var(--radius);
  max-width: 560px;
  width: 100%;
  max-height: 85vh;
  overflow-y: auto;
  position: relative;
  transform: translateY(20px);
  transition: transform 0.25s;
}

.modal-overlay.active .modal-content {
  transform: translateY(0);
}

.modal-close {
  position: absolute;
  top: 0.5rem;
  right: 0.75rem;
  background: rgba(0, 0, 0, 0.5);
  border: none;
  color: #fff;
  font-size: 1.5rem;
  width: 2rem;
  height: 2rem;
  border-radius: 50%;
  cursor: pointer;
  display: flex;
  align-items: center;
  justify-content: center;
  line-height: 1;
  z-index: 1;
  transition: background 0.2s;
}

.modal-close:hover {
  background: rgba(0, 0, 0, 0.7);
}

.modal-img {
  width: 100%;
  display: block;
  border-radius: var(--radius) var(--radius) 0 0;
}

.modal-content h3 {
  font-size: 1.2rem;
  font-weight: 700;
  padding: 1.25rem 1.5rem 0.5rem;
  color: var(--color-text);
}

.modal-content p {
  font-size: 0.9rem;
  color: var(--color-muted);
  line-height: 1.7;
  padding: 0 1.5rem;
}

.modal-links {
  display: flex;
  gap: 1rem;
  flex-wrap: wrap;
  padding: 1rem 1.5rem 1.5rem;
}

.modal-links a {
  font-size: 0.85rem;
  color: var(--color-accent);
  font-weight: 500;
  text-decoration: none;
  transition: opacity 0.2s;
}

.modal-links a:hover {
  opacity: 0.7;
}

@media (max-width: 768px) {
  .products-grid {
    grid-template-columns: repeat(2, 1fr);
  }
}

@media (max-width: 640px) {
  .section {
    padding: 3rem 0;
  }

  .pub-item {
    flex-direction: column;
    gap: 0.25rem;
  }

  .pub-date {
    width: auto;
  }

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

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

  .product-thumb {
    height: 180px;
  }

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

  .hero-contact {
    flex-direction: column;
    gap: 0.25rem;
  }
}