/* ================================================================
   DESIGN TOKENS
   ================================================================ */

:root {
  /* Type Scale (fluid) */
  --text-xs:   clamp(0.75rem,  0.7rem  + 0.25vw, 0.875rem);
  --text-sm:   clamp(0.875rem, 0.8rem  + 0.35vw, 1rem);
  --text-base: clamp(1rem,     0.95rem + 0.25vw, 1.125rem);
  --text-lg:   clamp(1.125rem, 1rem    + 0.75vw, 1.5rem);
  --text-xl:   clamp(1.5rem,   1.2rem  + 1.25vw, 2.25rem);
  --text-2xl:  clamp(2rem,     1.2rem  + 2.5vw,  3.5rem);
  --text-3xl:  clamp(2.5rem,   1rem    + 4vw,    5rem);
  --text-hero: clamp(3rem,     0.5rem  + 7vw,    8rem);

  /* Spacing (4px base) */
  --space-1:  0.25rem;
  --space-2:  0.5rem;
  --space-3:  0.75rem;
  --space-4:  1rem;
  --space-5:  1.25rem;
  --space-6:  1.5rem;
  --space-8:  2rem;
  --space-10: 2.5rem;
  --space-12: 3rem;
  --space-16: 4rem;
  --space-20: 5rem;
  --space-24: 6rem;
  --space-32: 8rem;

  /* Radius */
  --radius-sm: 0.375rem;
  --radius-md: 0.5rem;
  --radius-lg: 0.75rem;
  --radius-xl: 1rem;
  --radius-full: 9999px;

  /* Transition */
  --transition-interactive: 180ms cubic-bezier(0.16, 1, 0.3, 1);
  --ease-out: cubic-bezier(0.16, 1, 0.3, 1);

  /* Content widths */
  --content-narrow: 640px;
  --content-default: 960px;
  --content-wide: 1200px;

  /* Fonts */
  --font-display: 'Cabinet Grotesk', 'Inter', sans-serif;
  --font-body: 'Satoshi', 'Inter', sans-serif;
}

/* ================================================================
   LIGHT MODE (default)
   ================================================================ */
:root, [data-theme="light"] {
  --color-bg:           #0c0f14;
  --color-surface:      #141820;
  --color-surface-2:    #1a1f2b;
  --color-border:       #2a3040;
  --color-divider:      #222836;
  --color-text:         #e4e6ec;
  --color-text-muted:   #8b90a0;
  --color-text-faint:   #555b6e;
  --color-primary:      #3b82f6;
  --color-primary-hover:#2563eb;
  --color-primary-glow: rgba(59, 130, 246, 0.15);
  --color-primary-glow-strong: rgba(59, 130, 246, 0.25);

  --shadow-sm: 0 1px 2px rgba(0,0,0,0.3);
  --shadow-md: 0 4px 12px rgba(0,0,0,0.4);
  --shadow-lg: 0 12px 32px rgba(0,0,0,0.5);
}

/* ================================================================
   DARK MODE — same as default since the design IS dark
   ================================================================ */
[data-theme="dark"] {
  --color-bg:           #0c0f14;
  --color-surface:      #141820;
  --color-surface-2:    #1a1f2b;
  --color-border:       #2a3040;
  --color-divider:      #222836;
  --color-text:         #e4e6ec;
  --color-text-muted:   #8b90a0;
  --color-text-faint:   #555b6e;
  --color-primary:      #3b82f6;
  --color-primary-hover:#2563eb;
  --color-primary-glow: rgba(59, 130, 246, 0.15);
  --color-primary-glow-strong: rgba(59, 130, 246, 0.25);

  --shadow-sm: 0 1px 2px rgba(0,0,0,0.3);
  --shadow-md: 0 4px 12px rgba(0,0,0,0.4);
  --shadow-lg: 0 12px 32px rgba(0,0,0,0.5);
}

/* LIGHT MODE */
[data-theme="light"] {
  --color-bg:           #f5f6fa;
  --color-surface:      #ffffff;
  --color-surface-2:    #eef0f5;
  --color-border:       #d0d5e0;
  --color-divider:      #dde0e8;
  --color-text:         #1a1d26;
  --color-text-muted:   #5c6070;
  --color-text-faint:   #9098a8;
  --color-primary:      #2563eb;
  --color-primary-hover:#1d4ed8;
  --color-primary-glow: rgba(37, 99, 235, 0.1);
  --color-primary-glow-strong: rgba(37, 99, 235, 0.18);

  --shadow-sm: 0 1px 3px rgba(0,0,0,0.06);
  --shadow-md: 0 4px 12px rgba(0,0,0,0.08);
  --shadow-lg: 0 12px 32px rgba(0,0,0,0.12);
}


/* ================================================================
   HEADER / NAV
   ================================================================ */
.site-header {
  position: fixed;
  top: 0;
  left: 0;
  right: 0;
  z-index: 100;
  background: color-mix(in srgb, var(--color-bg) 85%, transparent);
  backdrop-filter: blur(16px);
  -webkit-backdrop-filter: blur(16px);
  border-bottom: 1px solid var(--color-divider);
  transition: transform 0.3s var(--ease-out), box-shadow 0.3s var(--ease-out);
}

.site-header--hidden {
  transform: translateY(-100%);
}

.site-header--scrolled {
  box-shadow: var(--shadow-md);
}

.header-inner {
  max-width: var(--content-wide);
  margin-inline: auto;
  padding: var(--space-3) var(--space-4);
  display: flex;
  align-items: center;
  justify-content: space-between;
}

.header-logo {
  font-family: var(--font-display);
  font-weight: 700;
  font-size: var(--text-lg);
  color: var(--color-text);
  text-decoration: none;
  letter-spacing: -0.02em;
}

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

.nav-list {
  display: flex;
  gap: var(--space-6);
  list-style: none;
}

.nav-link {
  font-size: var(--text-sm);
  color: var(--color-text-muted);
  text-decoration: none;
  position: relative;
  padding-bottom: var(--space-1);
  transition: color var(--transition-interactive);
}

.nav-link::after {
  content: '';
  position: absolute;
  bottom: 0;
  left: 0;
  width: 0;
  height: 2px;
  background: var(--color-primary);
  transition: width 0.3s var(--ease-out);
}

.nav-link:hover,
.nav-link.active {
  color: var(--color-text);
}

.nav-link:hover::after,
.nav-link.active::after {
  width: 100%;
}

.theme-toggle {
  display: flex;
  align-items: center;
  justify-content: center;
  width: 40px;
  height: 40px;
  border-radius: var(--radius-md);
  color: var(--color-text-muted);
  transition: color var(--transition-interactive), background var(--transition-interactive);
}

.theme-toggle:hover {
  color: var(--color-text);
  background: var(--color-surface-2);
}

.hamburger {
  display: none;
  flex-direction: column;
  gap: 5px;
  width: 24px;
  padding: var(--space-2);
  box-sizing: content-box;
}

.hamburger span {
  display: block;
  width: 100%;
  height: 2px;
  background: var(--color-text);
  border-radius: 2px;
  transition: transform 0.3s var(--ease-out), opacity 0.3s var(--ease-out);
}

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

.mobile-nav {
  display: none;
  position: fixed;
  top: 0;
  left: 0;
  right: 0;
  bottom: 0;
  z-index: 99;
  background: color-mix(in srgb, var(--color-bg) 95%, transparent);
  backdrop-filter: blur(20px);
  -webkit-backdrop-filter: blur(20px);
  flex-direction: column;
  align-items: center;
  justify-content: center;
  gap: var(--space-8);
}

.mobile-nav.is-open {
  display: flex;
}

.mobile-nav a {
  font-family: var(--font-display);
  font-size: var(--text-xl);
  color: var(--color-text);
  text-decoration: none;
  transition: color var(--transition-interactive);
}

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

@media (max-width: 768px) {
  .nav-list { display: none; }
  .hamburger { display: flex; }
}


/* ================================================================
   HERO
   ================================================================ */
.hero {
  min-height: 100dvh;
  display: flex;
  flex-direction: column;
  align-items: center;
  justify-content: center;
  text-align: center;
  padding: var(--space-32) var(--space-4) var(--space-16);
  position: relative;
  overflow: hidden;
}

.hero::before {
  content: '';
  position: absolute;
  top: 50%;
  left: 50%;
  transform: translate(-50%, -50%);
  width: 600px;
  height: 600px;
  background: radial-gradient(circle, var(--color-primary-glow-strong) 0%, transparent 70%);
  border-radius: 50%;
  pointer-events: none;
  z-index: 0;
}

.hero-content {
  position: relative;
  z-index: 1;
}

.hero-badge {
  display: inline-flex;
  align-items: center;
  gap: var(--space-2);
  padding: var(--space-1) var(--space-4);
  border: 1px solid var(--color-border);
  border-radius: var(--radius-full);
  font-size: var(--text-xs);
  color: var(--color-text-muted);
  margin-bottom: var(--space-8);
  background: var(--color-surface);
}

.hero-badge .dot {
  width: 8px;
  height: 8px;
  border-radius: 50%;
  background: #22c55e;
  animation: pulse-dot 2s ease-in-out infinite;
}

@keyframes pulse-dot {
  0%, 100% { opacity: 1; }
  50% { opacity: 0.4; }
}

.hero-name {
  font-family: var(--font-display);
  font-size: var(--text-hero);
  font-weight: 800;
  letter-spacing: -0.03em;
  line-height: 1.05;
  color: var(--color-text);
  margin-bottom: var(--space-4);
}

.hero-name .highlight {
  background: linear-gradient(135deg, var(--color-primary), #60a5fa);
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
  background-clip: text;
}

.hero-subtitle {
  font-size: var(--text-lg);
  color: var(--color-text-muted);
  max-width: 600px;
  margin-inline: auto;
  margin-bottom: var(--space-8);
  font-weight: 400;
}

.hero-cta-group {
  display: flex;
  gap: var(--space-4);
  justify-content: center;
  flex-wrap: wrap;
}

.scroll-indicator {
  position: absolute;
  bottom: var(--space-8);
  left: 50%;
  transform: translateX(-50%);
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: var(--space-2);
  color: var(--color-text-faint);
  font-size: var(--text-xs);
}

.scroll-indicator-line {
  width: 1px;
  height: 40px;
  background: linear-gradient(to bottom, var(--color-primary), transparent);
  animation: scroll-pulse 2s ease-in-out infinite;
}

@keyframes scroll-pulse {
  0%, 100% { opacity: 1; transform: scaleY(1); }
  50% { opacity: 0.3; transform: scaleY(0.6); }
}


/* ================================================================
   BUTTONS
   ================================================================ */
.btn {
  display: inline-flex;
  align-items: center;
  gap: var(--space-2);
  padding: var(--space-3) var(--space-6);
  border-radius: var(--radius-md);
  font-size: var(--text-sm);
  font-weight: 500;
  text-decoration: none;
  cursor: pointer;
  transition: all var(--transition-interactive);
}

.btn-primary {
  background: var(--color-primary);
  color: #fff;
  border: none;
}

.btn-primary:hover {
  background: var(--color-primary-hover);
  transform: translateY(-1px);
  box-shadow: 0 4px 20px var(--color-primary-glow-strong);
}

.btn-primary:active {
  transform: translateY(0);
}

.btn-secondary {
  background: transparent;
  color: var(--color-text);
  border: 1px solid var(--color-border);
}

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

.btn-secondary:active {
  transform: translateY(0);
}


/* ================================================================
   SECTION BASE
   ================================================================ */
.section {
  padding: clamp(var(--space-12), 8vw, var(--space-24)) var(--space-4);
}

.section-inner {
  max-width: var(--content-wide);
  margin-inline: auto;
}

.section-label {
  display: inline-block;
  font-size: var(--text-xs);
  font-weight: 600;
  text-transform: uppercase;
  letter-spacing: 0.1em;
  color: var(--color-primary);
  margin-bottom: var(--space-3);
}

.section-title {
  font-family: var(--font-display);
  font-size: var(--text-xl);
  font-weight: 700;
  letter-spacing: -0.02em;
  color: var(--color-text);
  margin-bottom: var(--space-2);
}

.section-desc {
  font-size: var(--text-base);
  color: var(--color-text-muted);
  max-width: 600px;
  margin-bottom: var(--space-10);
}


/* ================================================================
   EXPERIENCE CARDS
   ================================================================ */
.experience-grid {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(min(340px, 100%), 1fr));
  gap: var(--space-6);
}

.exp-card {
  background: var(--color-surface);
  border: 1px solid var(--color-border);
  border-radius: var(--radius-lg);
  padding: var(--space-6);
  transition: border-color var(--transition-interactive),
              box-shadow var(--transition-interactive),
              transform var(--transition-interactive);
}

.exp-card:hover {
  border-color: var(--color-primary);
  box-shadow: 0 0 0 1px var(--color-primary), 0 8px 30px var(--color-primary-glow);
  transform: translateY(-2px);
}

.exp-card-image {
  width: 100%;
  height: 180px;
  background: var(--color-surface-2);
  border-radius: var(--radius-md);
  margin-bottom: var(--space-4);
  display: flex;
  align-items: center;
  justify-content: center;
  overflow: hidden;
}

.exp-card-image svg {
  width: 48px;
  height: 48px;
  color: var(--color-text-faint);
}

.exp-card-title {
  font-family: var(--font-display);
  font-size: var(--text-lg);
  font-weight: 600;
  color: var(--color-text);
  margin-bottom: var(--space-2);
}

.exp-card-text {
  font-size: var(--text-sm);
  color: var(--color-text-muted);
  line-height: 1.7;
}

.exp-card-tag {
  display: inline-block;
  font-size: var(--text-xs);
  color: var(--color-primary);
  background: var(--color-primary-glow);
  padding: var(--space-1) var(--space-3);
  border-radius: var(--radius-full);
  margin-top: var(--space-3);
  font-weight: 500;
}


/* ================================================================
   LANGUAGE CARDS
   ================================================================ */
.lang-grid {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(min(300px, 100%), 1fr));
  gap: var(--space-6);
}

.lang-card {
  background: var(--color-surface);
  border: 1px solid var(--color-border);
  border-radius: var(--radius-lg);
  padding: var(--space-6);
  display: flex;
  gap: var(--space-5);
  align-items: flex-start;
  transition: border-color var(--transition-interactive),
              box-shadow var(--transition-interactive),
              transform var(--transition-interactive);
}

.lang-card:hover {
  border-color: var(--color-primary);
  box-shadow: 0 0 0 1px var(--color-primary), 0 8px 30px var(--color-primary-glow);
  transform: translateY(-2px);
}

.lang-icon {
  width: 56px;
  height: 56px;
  flex-shrink: 0;
  border-radius: var(--radius-md);
  background: var(--color-primary-glow);
  display: flex;
  align-items: center;
  justify-content: center;
  font-size: 1.5rem;
  color: var(--color-primary);
}

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

.lang-card-title {
  font-family: var(--font-display);
  font-size: var(--text-lg);
  font-weight: 600;
  color: var(--color-text);
  margin-bottom: var(--space-1);
}

.lang-card-text {
  font-size: var(--text-sm);
  color: var(--color-text-muted);
  line-height: 1.7;
}


/* ================================================================
   PAPERS
   ================================================================ */
.papers-grid {
  display: grid;
  gap: var(--space-6);
}

.paper-card {
  background: var(--color-surface);
  border: 1px solid var(--color-border);
  border-radius: var(--radius-lg);
  padding: var(--space-6);
  display: grid;
  grid-template-columns: 200px 1fr;
  gap: var(--space-6);
  transition: border-color var(--transition-interactive),
              box-shadow var(--transition-interactive),
              transform var(--transition-interactive);
}

.paper-card:hover {
  border-color: var(--color-primary);
  box-shadow: 0 0 0 1px var(--color-primary), 0 8px 30px var(--color-primary-glow);
  transform: translateY(-2px);
}

.paper-image {
  width: 100%;
  aspect-ratio: 4/5;
  background: var(--color-surface-2);
  border-radius: var(--radius-md);
  display: flex;
  align-items: center;
  justify-content: center;
}

.paper-image svg {
  width: 40px;
  height: 40px;
  color: var(--color-text-faint);
}

.paper-body {
  display: flex;
  flex-direction: column;
  justify-content: center;
}

.paper-type {
  font-size: var(--text-xs);
  font-weight: 600;
  text-transform: uppercase;
  letter-spacing: 0.08em;
  color: var(--color-primary);
  margin-bottom: var(--space-2);
}

.paper-title {
  font-family: var(--font-display);
  font-size: var(--text-lg);
  font-weight: 600;
  color: var(--color-text);
  margin-bottom: var(--space-3);
}

.paper-abstract {
  font-size: var(--text-sm);
  color: var(--color-text-muted);
  line-height: 1.7;
}

@media (max-width: 640px) {
  .paper-card {
    grid-template-columns: 1fr;
  }
  .paper-image {
    aspect-ratio: 16/9;
    max-height: 180px;
  }
}


/* ================================================================
   EDUCATION TIMELINE
   ================================================================ */
.timeline {
  position: relative;
  padding-left: var(--space-8);
}

.timeline::before {
  content: '';
  position: absolute;
  left: 15px;
  top: 0;
  bottom: 0;
  width: 2px;
  background: linear-gradient(to bottom, var(--color-primary), var(--color-border));
}

.timeline-item {
  position: relative;
  padding-bottom: var(--space-10);
}

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

.timeline-dot {
  position: absolute;
  left: calc(-1 * var(--space-8) + 8px);
  top: 6px;
  width: 16px;
  height: 16px;
  border-radius: 50%;
  background: var(--color-bg);
  border: 3px solid var(--color-primary);
  z-index: 1;
}

.timeline-item.wip .timeline-dot {
  background: var(--color-primary);
  box-shadow: 0 0 0 4px var(--color-primary-glow-strong);
  animation: pulse-dot 2s ease-in-out infinite;
}

.timeline-card {
  background: var(--color-surface);
  border: 1px solid var(--color-border);
  border-radius: var(--radius-lg);
  padding: var(--space-5);
  display: flex;
  gap: var(--space-4);
  align-items: flex-start;
  transition: border-color var(--transition-interactive),
              box-shadow var(--transition-interactive);
}

.timeline-card:hover {
  border-color: var(--color-primary);
  box-shadow: 0 4px 20px var(--color-primary-glow);
}

.timeline-icon {
  width: 44px;
  height: 44px;
  flex-shrink: 0;
  border-radius: var(--radius-md);
  background: var(--color-primary-glow);
  display: flex;
  align-items: center;
  justify-content: center;
  font-size: 1.25rem;
}

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

.timeline-year {
  font-size: var(--text-xs);
  font-weight: 600;
  color: var(--color-primary);
  margin-bottom: var(--space-1);
}

.timeline-title {
  font-family: var(--font-display);
  font-size: var(--text-base);
  font-weight: 600;
  color: var(--color-text);
  margin-bottom: var(--space-1);
}

.timeline-text {
  font-size: var(--text-sm);
  color: var(--color-text-muted);
  line-height: 1.6;
}

.wip-badge {
  display: inline-block;
  font-size: var(--text-xs);
  font-weight: 600;
  color: var(--color-primary);
  background: var(--color-primary-glow);
  padding: var(--space-1) var(--space-3);
  border-radius: var(--radius-full);
  margin-top: var(--space-2);
}


/* ================================================================
   CONTACT
   ================================================================ */
.contact-section {
  text-align: center;
}

.contact-section .section-desc {
  margin-inline: auto;
}

.contact-cta-group {
  display: flex;
  gap: var(--space-4);
  justify-content: center;
  flex-wrap: wrap;
  margin-top: var(--space-6);
}


/* ================================================================
   FOOTER
   ================================================================ */
.site-footer {
  border-top: 1px solid var(--color-divider);
  padding: var(--space-8) var(--space-4);
  text-align: center;
}

.footer-inner {
  max-width: var(--content-wide);
  margin-inline: auto;
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: var(--space-3);
}

.footer-text {
  font-size: var(--text-xs);
  color: var(--color-text-faint);
}

.footer-text a {
  color: var(--color-text-muted);
  text-decoration: none;
  transition: color var(--transition-interactive);
}

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


/* ================================================================
   BACK TO TOP
   ================================================================ */
.back-to-top {
  position: fixed;
  bottom: var(--space-6);
  right: var(--space-6);
  width: 44px;
  height: 44px;
  border-radius: var(--radius-full);
  background: var(--color-primary);
  color: #fff;
  display: flex;
  align-items: center;
  justify-content: center;
  z-index: 90;
  opacity: 0;
  transform: translateY(16px);
  pointer-events: none;
  transition: opacity 0.3s var(--ease-out),
              transform 0.3s var(--ease-out),
              background 0.2s var(--ease-out);
  box-shadow: 0 4px 16px var(--color-primary-glow-strong);
}

.back-to-top.visible {
  opacity: 1;
  transform: translateY(0);
  pointer-events: auto;
}

.back-to-top:hover {
  background: var(--color-primary-hover);
  transform: translateY(-2px);
}

.back-to-top:active {
  transform: translateY(0);
}


/* ================================================================
   SCROLL REVEAL (CSS-only fade-in)
   ================================================================ */
.fade-in {
  opacity: 1;
}

@supports (animation-timeline: scroll()) {
  .fade-in {
    opacity: 0;
    animation: reveal-fade linear both;
    animation-timeline: view();
    animation-range: entry 0% entry 80%;
  }
}

@keyframes reveal-fade {
  to { opacity: 1; }
}

/* JS fallback for browsers without scroll-driven animations */
.fade-in-js {
  opacity: 0;
  transition: opacity 0.6s var(--ease-out);
}

.fade-in-js.is-visible {
  opacity: 1;
}


/* ================================================================
   DIVIDER
   ================================================================ */
.section-divider {
  max-width: var(--content-wide);
  margin-inline: auto;
  border: none;
  border-top: 1px solid var(--color-divider);
}