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

:root {
  --color-bg: #0d1117;
  --color-bg-alt: #161b22;
  --color-text: #e6edf3;
  --color-text-muted: #8b949e;
  --color-accent: #7aa2f7;
  --color-accent-light: rgba(122, 162, 247, 0.15);
  --color-accent-hover: #9db8fa;
  --color-border: #21262d;
  --color-card-bg: #161b22;
  --color-card-shadow: rgba(0, 0, 0, 0.4);

  --font-family: 'Inter', -apple-system, BlinkMacSystemFont, 'Segoe UI', sans-serif;
  --font-size-sm: 0.875rem;
  --font-size-base: 1rem;
  --font-size-lg: 1.125rem;
  --font-size-xl: 1.5rem;
  --font-size-2xl: 2rem;
  --font-size-3xl: 2.75rem;
  --font-weight-normal: 400;
  --font-weight-medium: 500;
  --font-weight-semibold: 600;
  --font-weight-bold: 700;
  --line-height-body: 1.7;
  --line-height-heading: 1.2;

  --space-xs: 0.25rem;
  --space-sm: 0.5rem;
  --space-md: 1rem;
  --space-lg: 1.5rem;
  --space-xl: 2rem;
  --space-2xl: 3rem;
  --space-3xl: 4rem;
  --space-4xl: 6rem;

  --container-max: 1100px;
  --container-narrow: 800px;
  --navbar-height: 64px;
  --border-radius: 8px;
  --border-radius-lg: 12px;

  --transition-fast: 150ms ease;
  --transition-base: 250ms ease;
  --transition-slow: 400ms ease;
}

[data-theme="light"] {
  --color-bg: #ffffff;
  --color-bg-alt: #f6f8fa;
  --color-text: #1f2328;
  --color-text-muted: #656d76;
  --color-accent: #2563eb;
  --color-accent-light: rgba(37, 99, 235, 0.1);
  --color-accent-hover: #1d4ed8;
  --color-border: #d0d7de;
  --color-card-bg: #ffffff;
  --color-card-shadow: rgba(0, 0, 0, 0.08);
}

/* ============================================
   RESET & BASE
   ============================================ */

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

html {
  scroll-behavior: smooth;
}

@media (prefers-reduced-motion: reduce) {
  html {
    scroll-behavior: auto;
  }
  .fade-in {
    opacity: 1 !important;
    transform: none !important;
    transition: none !important;
  }
}

body {
  font-family: var(--font-family);
  color: var(--color-text);
  background: var(--color-bg);
  line-height: var(--line-height-body);
  padding-top: var(--navbar-height);
  -webkit-font-smoothing: antialiased;
  -moz-osx-font-smoothing: grayscale;
}

section {
  scroll-margin-top: calc(var(--navbar-height) + 1rem);
}

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

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

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

h1, h2, h3, h4 {
  line-height: var(--line-height-heading);
  font-weight: var(--font-weight-semibold);
  color: var(--color-text);
}

ul {
  list-style: none;
}

/* ============================================
   LAYOUT
   ============================================ */

.container {
  max-width: var(--container-max);
  margin: 0 auto;
  padding: 0 var(--space-lg);
}

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

.section {
  padding: var(--space-4xl) 0;
  position: relative;
  z-index: 1;
}

.section__heading {
  font-size: var(--font-size-2xl);
  font-weight: var(--font-weight-bold);
  margin-bottom: var(--space-2xl);
  text-align: center;
  letter-spacing: -0.5px;
}

.section__cta {
  text-align: center;
  margin-top: var(--space-3xl);
}

/* ============================================
   NAVBAR
   ============================================ */

.navbar {
  position: fixed;
  top: 0;
  left: 0;
  right: 0;
  height: var(--navbar-height);
  background: transparent;
  border-bottom: 1px solid transparent;
  z-index: 100;
  display: flex;
  align-items: center;
  padding: 0 var(--space-lg);
  transition: background var(--transition-base), border-color var(--transition-base);
}

.navbar--scrolled {
  background: rgba(13, 17, 23, 0.85);
  backdrop-filter: blur(12px);
  -webkit-backdrop-filter: blur(12px);
  border-bottom-color: var(--color-border);
}

[data-theme="light"] .navbar--scrolled {
  background: rgba(210, 230, 248, 0.8);
}

.navbar__inner {
  display: flex;
  align-items: center;
  justify-content: space-between;
  width: 100%;
}

.navbar__brand {
  font-weight: var(--font-weight-bold);
  color: #ffffff;
  text-decoration: none;
  font-size: var(--font-size-lg);
  display: inline-flex;
  align-items: center;
  gap: var(--space-sm);
  transition: color var(--transition-base);
}

.navbar__logo {
  width: 28px;
  height: 28px;
  object-fit: contain;
}

.navbar__brand:hover {
  color: #ffffff;
}

[data-theme="light"] .navbar__brand,
[data-theme="light"] .navbar__brand:hover {
  color: var(--color-text);
}

.navbar--scrolled .navbar__brand {
  color: var(--color-text);
}

.navbar--scrolled .navbar__brand:hover {
  color: var(--color-text);
}

.navbar__links {
  display: flex;
  gap: var(--space-xl);
  align-items: center;
}

.navbar__link {
  color: rgba(255, 255, 255, 0.7);
  text-decoration: none;
  font-size: var(--font-size-sm);
  font-weight: var(--font-weight-medium);
  transition: color var(--transition-fast);
  letter-spacing: 0.2px;
}

.navbar__link:hover,
.navbar__link--active {
  color: #ffffff;
}

[data-theme="light"] .navbar__link {
  color: var(--color-text-muted);
}

[data-theme="light"] .navbar__link:hover,
[data-theme="light"] .navbar__link--active {
  color: var(--color-accent);
}

.navbar--scrolled .navbar__link {
  color: var(--color-text-muted);
}

.navbar--scrolled .navbar__link:hover,
.navbar--scrolled .navbar__link--active {
  color: var(--color-accent);
}

.navbar__toggle {
  display: none;
  background: none;
  border: none;
  cursor: pointer;
  padding: var(--space-sm);
  flex-direction: column;
  gap: 5px;
}

.navbar__toggle span {
  display: block;
  width: 22px;
  height: 2px;
  background: #ffffff;
  border-radius: 2px;
  transition: all var(--transition-base);
}

[data-theme="light"] .navbar__toggle span {
  background: var(--color-text);
}

.navbar--scrolled .navbar__toggle span {
  background: var(--color-text);
}

/* ============================================
   HERO
   ============================================ */

.hero {
  min-height: 100vh;
  margin-top: calc(-1 * var(--navbar-height));
  display: flex;
  align-items: center;
  position: relative;
}

.starfield {
  position: fixed;
  top: 0;
  left: 0;
  pointer-events: none;
  z-index: 0;
}

[data-theme="light"] .starfield {
  opacity: 1;
}

.hero__inner {
  display: grid;
  grid-template-columns: auto 1fr;
  align-items: center;
  gap: var(--space-3xl);
  padding: var(--space-4xl) 0;
  position: relative;
  z-index: 1;
}

.hero__photo {
  width: 200px;
  height: 200px;
  border-radius: 50%;
  object-fit: cover;
  object-position: 35% center;
  border: 3px solid rgba(255, 255, 255, 0.15);
  box-shadow: 0 0 40px rgba(122, 162, 247, 0.15);
}

.hero__name {
  font-size: var(--font-size-3xl);
  font-weight: var(--font-weight-bold);
  letter-spacing: -1px;
  margin-bottom: var(--space-sm);
  color: #ffffff;
}

.hero__tagline {
  font-size: var(--font-size-lg);
  color: rgba(255, 255, 255, 0.6);
  margin-bottom: var(--space-lg);
}

.hero__socials {
  display: flex;
  gap: var(--space-md);
}

.hero .social-link {
  color: rgba(255, 255, 255, 0.5);
}

[data-theme="light"] .hero__photo {
  border-color: var(--color-border);
  box-shadow: 0 0 40px rgba(0, 0, 0, 0.1);
}

[data-theme="light"] .hero__name {
  color: var(--color-text);
}

[data-theme="light"] .hero__tagline {
  color: var(--color-text-muted);
}

[data-theme="light"] .hero .social-link {
  color: var(--color-text-muted);
}

.hero .social-link:hover {
  color: var(--color-accent);
}

/* ============================================
   SOCIAL LINKS
   ============================================ */

.social-link {
  color: var(--color-text-muted);
  transition: color var(--transition-fast);
  display: inline-flex;
  align-items: center;
}

.social-link:hover {
  color: var(--color-accent);
}

.social-link i {
  font-size: 1.4rem;
}

/* ============================================
   ABOUT
   ============================================ */

#about {
  min-height: calc(100vh - var(--navbar-height));
  display: flex;
  align-items: center;
  justify-content: center;
}

.about__text {
  max-width: var(--container-narrow);
  margin: 0 auto;
  font-size: var(--font-size-lg);
  color: var(--color-text-muted);
  text-align: center;
}

.about__text p {
  margin-bottom: var(--space-lg);
}

.about__text p:last-child {
  margin-bottom: 0;
}

/* ============================================
   TIMELINE
   ============================================ */

.timeline {
  position: relative;
  padding-left: 2rem;
  max-width: 700px;
  margin: 0 auto;
}

.timeline::before {
  content: '';
  position: absolute;
  left: 7px;
  top: 8px;
  bottom: 0;
  width: 2px;
  background: var(--color-border);
}

.timeline__item {
  position: relative;
  padding-bottom: var(--space-2xl);
  padding-left: var(--space-xl);
}

.timeline__item:last-child {
  padding-bottom: 0;
}

.timeline__dot {
  position: absolute;
  left: calc(-2rem);
  top: 6px;
  width: 16px;
  height: 16px;
  border-radius: 50%;
  background: var(--color-accent);
  border: 3px solid var(--color-bg);
  box-shadow: 0 0 0 2px var(--color-border);
}

.timeline__badge {
  display: inline-block;
  font-size: 0.7rem;
  padding: 2px 10px;
  border-radius: 4px;
  font-weight: var(--font-weight-semibold);
  text-transform: uppercase;
  letter-spacing: 0.8px;
  margin-bottom: var(--space-xs);
}

.timeline__badge--work {
  background: rgba(45, 212, 191, 0.15);
  color: #2dd4bf;
}

.timeline__badge--project {
  background: rgba(167, 139, 250, 0.15);
  color: #a78bfa;
}

.timeline__badge--internship {
  background: rgba(56, 189, 248, 0.15);
  color: #38bdf8;
}

.timeline__badge--research {
  background: rgba(129, 140, 248, 0.15);
  color: #818cf8;
}

[data-theme="light"] .timeline__badge--work {
  background: rgba(5, 150, 105, 0.1);
  color: #059669;
}

[data-theme="light"] .timeline__badge--project {
  background: rgba(109, 40, 217, 0.1);
  color: #6d28d9;
}

[data-theme="light"] .timeline__badge--internship {
  background: rgba(37, 99, 235, 0.1);
  color: #2563eb;
}

[data-theme="light"] .timeline__badge--research {
  background: rgba(79, 70, 229, 0.1);
  color: #4f46e5;
}

.timeline__title {
  font-size: var(--font-size-lg);
  font-weight: var(--font-weight-semibold);
  margin: var(--space-xs) 0;
}

.timeline__title a {
  color: var(--color-text);
  text-decoration: none;
  transition: color var(--transition-fast);
}

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

.timeline__date {
  font-size: var(--font-size-sm);
  color: var(--color-text-muted);
  display: block;
  margin-bottom: var(--space-xs);
}

.timeline__desc {
  color: var(--color-text-muted);
  font-size: var(--font-size-sm);
  margin: 0;
}

/* ============================================
   DETAIL PAGE LAYOUT
   ============================================ */

.detail-page {
  padding: var(--space-3xl) 0 var(--space-4xl);
}

.detail-header__back {
  display: inline-flex;
  align-items: center;
  gap: var(--space-sm);
  color: var(--color-accent);
  font-size: var(--font-size-sm);
  font-weight: var(--font-weight-medium);
  margin-bottom: var(--space-2xl);
  text-decoration: none;
}

.detail-header__back:hover {
  color: var(--color-accent-hover);
}

.detail-header {
  text-align: center;
  margin-bottom: var(--space-2xl);
}

.detail-header__title {
  font-size: var(--font-size-3xl);
  font-weight: var(--font-weight-bold);
  letter-spacing: -0.5px;
  margin-bottom: var(--space-md);
}

.detail-header__meta {
  display: flex;
  align-items: center;
  justify-content: center;
  gap: var(--space-md);
  flex-wrap: wrap;
}

.meta-badge {
  display: inline-flex;
  align-items: center;
  gap: var(--space-sm);
  background: var(--color-bg-alt);
  color: var(--color-text-muted);
  padding: 6px 14px;
  border-radius: 20px;
  font-size: var(--font-size-sm);
  font-weight: var(--font-weight-medium);
}

/* ============================================
   INTRO CARD (Detail Pages)
   ============================================ */

.intro-card {
  background: var(--color-card-bg);
  border: 1px solid var(--color-border);
  border-radius: var(--border-radius-lg);
  padding: var(--space-2xl);
  margin-bottom: var(--space-2xl);
  text-align: center;
  box-shadow: 0 1px 3px var(--color-card-shadow);
}

.intro-card__image {
  max-width: 500px;
  margin: 0 auto var(--space-xl);
  border-radius: var(--border-radius);
}

.intro-card__text {
  font-size: var(--font-size-lg);
  color: var(--color-text-muted);
  line-height: var(--line-height-body);
  max-width: 650px;
  margin: 0 auto;
}

/* ============================================
   TECHNOLOGY BADGES
   ============================================ */

.tech-badges {
  display: flex;
  flex-wrap: wrap;
  gap: var(--space-sm);
  justify-content: center;
  margin-bottom: var(--space-2xl);
}

.tech-badge {
  display: inline-flex;
  align-items: center;
  gap: var(--space-xs);
  padding: 6px 14px;
  border: 1px solid var(--color-border);
  border-radius: 20px;
  font-size: var(--font-size-sm);
  font-weight: var(--font-weight-medium);
  color: var(--color-text-muted);
  background: var(--color-bg);
}

/* ============================================
   DETAIL CARDS
   ============================================ */

.detail-cards {
  display: flex;
  flex-direction: column;
  gap: var(--space-lg);
  margin-bottom: var(--space-2xl);
}

.detail-card {
  background: var(--color-card-bg);
  border: 1px solid var(--color-border);
  border-radius: var(--border-radius-lg);
  padding: var(--space-xl);
  box-shadow: 0 1px 3px var(--color-card-shadow);
  transition: transform var(--transition-base), box-shadow var(--transition-base);
}

.detail-card:hover {
  transform: translateY(-3px);
  box-shadow: 0 4px 12px rgba(0, 0, 0, 0.08);
}

.detail-card__header {
  display: flex;
  align-items: flex-start;
  gap: var(--space-md);
}

.detail-card__icon {
  width: 40px;
  height: 40px;
  background: var(--color-accent-light);
  border-radius: var(--border-radius);
  display: flex;
  align-items: center;
  justify-content: center;
  color: var(--color-accent);
  flex-shrink: 0;
  font-size: 1.2rem;
}

.detail-card__title {
  font-size: var(--font-size-lg);
  font-weight: var(--font-weight-semibold);
  margin-bottom: var(--space-sm);
}

.detail-card__body {
  color: var(--color-text-muted);
  line-height: var(--line-height-body);
  font-size: 0.95rem;
  margin: 0;
}

/* ============================================
   REFLECTION CARD
   ============================================ */

.reflection-card {
  background: var(--color-card-bg);
  border: 1px solid var(--color-border);
  border-radius: var(--border-radius-lg);
  padding: var(--space-2xl);
  text-align: center;
  box-shadow: 0 1px 3px var(--color-card-shadow);
  margin-bottom: var(--space-2xl);
}

.reflection-card h2 {
  font-size: var(--font-size-xl);
  margin-bottom: var(--space-lg);
}

.reflection-card p {
  font-size: var(--font-size-lg);
  color: var(--color-text-muted);
  line-height: var(--line-height-body);
  max-width: 650px;
  margin: 0 auto;
}

.reflection-card p + p {
  margin-top: var(--space-lg);
}

.reflection-card__image {
  max-width: 500px;
  margin: var(--space-xl) auto 0;
  border-radius: var(--border-radius);
  background: var(--color-bg-alt);
  padding: var(--space-lg);
}

.reflection-card__advisors {
  margin-top: var(--space-lg);
  color: var(--color-text-muted);
  font-size: 0.95rem;
}

.reflection-card__advisors i {
  margin-right: var(--space-sm);
}

/* ============================================
   BUTTONS
   ============================================ */

.btn-outline {
  display: inline-flex;
  align-items: center;
  gap: var(--space-sm);
  padding: 12px 24px;
  border: 2px solid var(--color-accent);
  border-radius: var(--border-radius);
  color: var(--color-accent);
  font-weight: var(--font-weight-medium);
  font-size: var(--font-size-base);
  text-decoration: none;
  transition: all var(--transition-base);
  cursor: pointer;
  background: transparent;
}

.btn-outline:hover {
  background: var(--color-accent);
  color: white;
  transform: translateY(-2px);
  box-shadow: 0 4px 12px rgba(122, 162, 247, 0.3);
}

[data-theme="light"] .btn-outline:hover {
  box-shadow: 0 4px 12px rgba(37, 99, 235, 0.3);
}

/* ============================================
   DETAIL PAGE CTA
   ============================================ */

.detail-cta {
  text-align: center;
}

/* ============================================
   FOOTER
   ============================================ */

.footer {
  text-align: center;
  padding: var(--space-2xl) 0;
  border-top: 1px solid var(--color-border);
  position: relative;
  z-index: 1;
}

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

.footer p {
  color: var(--color-text-muted);
  font-size: var(--font-size-sm);
  margin: 0;
}

/* ============================================
   SECTION DIVIDER
   ============================================ */

.section-divider {
  width: 60px;
  height: 2px;
  background: var(--color-border);
  margin: 0 auto;
  position: relative;
  z-index: 1;
}

/* ============================================
   SCROLL ANIMATIONS
   ============================================ */

.fade-in {
  opacity: 0;
  transform: translateY(20px);
  transition: opacity var(--transition-slow), transform var(--transition-slow);
}

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

/* Stagger delays for grouped elements */
.fade-in:nth-child(2) { transition-delay: 80ms; }
.fade-in:nth-child(3) { transition-delay: 160ms; }
.fade-in:nth-child(4) { transition-delay: 240ms; }
.fade-in:nth-child(5) { transition-delay: 320ms; }

/* ============================================
   RESPONSIVE — MOBILE
   ============================================ */

@media (max-width: 768px) {
  :root {
    --font-size-3xl: 2rem;
    --font-size-2xl: 1.5rem;
    --space-4xl: 3rem;
    --space-3xl: 2.5rem;
  }

  /* Navbar mobile */
  .navbar__toggle {
    display: flex;
  }

  .navbar__links {
    display: none;
    position: absolute;
    top: var(--navbar-height);
    left: 0;
    right: 0;
    background: var(--color-bg);
    border-bottom: 1px solid var(--color-border);
    flex-direction: column;
    padding: var(--space-lg);
    gap: var(--space-md);
    box-shadow: 0 4px 12px rgba(0, 0, 0, 0.05);
  }

  .navbar__links--open {
    display: flex;
  }

  .navbar__links--open .navbar__link {
    color: var(--color-text-muted);
  }

  .navbar__links--open .navbar__link:hover,
  .navbar__links--open .navbar__link--active {
    color: var(--color-accent);
  }

  .navbar__link {
    font-size: var(--font-size-base);
    padding: var(--space-sm) 0;
  }

  /* Hero mobile */
  .hero__inner {
    grid-template-columns: 1fr;
    text-align: center;
    justify-items: center;
    gap: var(--space-xl);
    padding: var(--space-2xl) 0;
  }

  .hero__photo {
    width: 160px;
    height: 160px;
  }

  .hero__socials {
    justify-content: center;
  }

  /* Timeline mobile */
  .timeline {
    padding-left: 1.5rem;
  }

  .timeline__dot {
    left: calc(-1.5rem);
  }

  /* Tech badges mobile */
  .tech-badges {
    gap: var(--space-xs);
  }

  .tech-badge {
    font-size: 0.8rem;
    padding: 4px 10px;
  }

  /* Detail page mobile */
  .detail-header__title {
    font-size: var(--font-size-2xl);
  }

  .intro-card,
  .detail-card,
  .reflection-card {
    padding: var(--space-lg);
  }

  .intro-card__image,
  .reflection-card__image {
    max-width: 100%;
  }
}