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

/* ===== CSS Custom Properties — Light (default) ===== */
:root {
  --bg: #fafafa;
  --bg-secondary: #f0f0f2;
  --text: #111111;
  --text-secondary: #555555;
  --accent: #6366f1;
  --accent-hover: #4f46e5;
  --accent-glow: rgba(99, 102, 241, 0.15);
  --border: #e5e5e5;
  --card-bg: #ffffff;
  --card-shadow: 0 1px 3px rgba(0, 0, 0, 0.05);
  --card-shadow-hover: 0 8px 30px rgba(99, 102, 241, 0.1);
  --tag-bg: #eef2ff;
  --tag-text: #6366f1;
  --tag-active-bg: #6366f1;
  --tag-active-text: #ffffff;
  --timeline-line: #e5e5e5;
  --timeline-dot: #6366f1;
  --nav-bg: rgba(250, 250, 250, 0.8);
  --code-bg: #f0f0f2;
  --transition: 0.25s ease;
  --font-heading: "Sora", -apple-system, BlinkMacSystemFont, "Segoe UI", sans-serif;
  --font-body: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, Oxygen, Ubuntu, Cantarell, "Helvetica Neue", sans-serif;
}

/* ===== Dark Theme ===== */
[data-theme="dark"] {
  --bg: #0a0a0a;
  --bg-secondary: #141414;
  --text: #eeeeee;
  --text-secondary: #999999;
  --accent: #818cf8;
  --accent-hover: #a5b4fc;
  --accent-glow: rgba(129, 140, 248, 0.12);
  --border: #1f1f1f;
  --card-bg: #141414;
  --card-shadow: 0 1px 3px rgba(0, 0, 0, 0.3);
  --card-shadow-hover: 0 8px 30px rgba(129, 140, 248, 0.08);
  --tag-bg: #1e1b4b;
  --tag-text: #818cf8;
  --tag-active-bg: #818cf8;
  --tag-active-text: #0a0a0a;
  --timeline-line: #1f1f1f;
  --timeline-dot: #818cf8;
  --nav-bg: rgba(10, 10, 10, 0.85);
  --code-bg: #141414;
}

/* ===== Typography ===== */
html {
  scroll-behavior: smooth;
  scroll-padding-top: 80px;
}

body {
  font-family: var(--font-body);
  font-size: 16px;
  line-height: 1.6;
  color: var(--text);
  background-color: var(--bg);
  transition: background-color var(--transition), color var(--transition);
  -webkit-font-smoothing: antialiased;
  -moz-osx-font-smoothing: grayscale;
}

h1, h2, h3, h4 {
  font-family: var(--font-heading);
  line-height: 1.15;
  font-weight: 700;
  letter-spacing: -0.02em;
}

h1 { font-size: 2.5rem; }
h2 { font-size: 1.85rem; }
h3 { font-size: 1.25rem; }

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

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

/* ===== Layout ===== */
.container {
  max-width: 1100px;
  margin: 0 auto;
  padding: 0 24px;
}

.container--narrow {
  max-width: 800px;
}

section {
  padding: 64px 0;
}

.section-title {
  margin-bottom: 36px;
  position: relative;
  font-size: 1.85rem;
  letter-spacing: -0.03em;
}

.section-title::before {
  content: "";
  display: block;
  width: 32px;
  height: 3px;
  background: var(--accent);
  margin-bottom: 12px;
  border-radius: 2px;
}

/* ===== Keyframe Animations ===== */
@keyframes heroFadeUp {
  from {
    opacity: 0;
    transform: translateY(24px);
  }
  to {
    opacity: 1;
    transform: translateY(0);
  }
}

@keyframes heroFadeIn {
  from { opacity: 0; }
  to { opacity: 1; }
}

@keyframes staggerFadeUp {
  from {
    opacity: 0;
    transform: translateY(16px);
  }
  to {
    opacity: 1;
    transform: translateY(0);
  }
}

/* ===== Nav ===== */
.nav {
  position: fixed;
  top: 0;
  left: 0;
  right: 0;
  z-index: 100;
  background: var(--nav-bg);
  backdrop-filter: blur(16px);
  -webkit-backdrop-filter: blur(16px);
  border-bottom: 1px solid var(--border);
  transition: background-color var(--transition), border-color var(--transition);
}

.nav__inner {
  display: flex;
  align-items: center;
  justify-content: space-between;
  height: 60px;
}

.nav__logo {
  display: inline-flex;
  align-items: center;
  transition: transform 0.2s ease;
}

.nav__logo:hover {
  transform: scale(1.05);
}

.nav__links {
  display: flex;
  align-items: center;
  gap: 28px;
  list-style: none;
}

.nav__links a {
  color: var(--text-secondary);
  font-size: 0.88rem;
  font-weight: 500;
  transition: color var(--transition);
  position: relative;
}

.nav__links a::after {
  content: "";
  position: absolute;
  bottom: -4px;
  left: 0;
  width: 0;
  height: 2px;
  background: var(--accent);
  border-radius: 1px;
  transition: width var(--transition);
}

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

.nav__links a:hover::after {
  width: 100%;
}

.theme-toggle {
  background: none;
  border: 1px solid var(--border);
  border-radius: 8px;
  padding: 6px 8px;
  cursor: pointer;
  display: flex;
  align-items: center;
  justify-content: center;
  color: var(--text-secondary);
  transition: color var(--transition), border-color var(--transition), background-color var(--transition);
}

.theme-toggle:hover {
  color: var(--accent);
  border-color: var(--accent);
  background: var(--accent-glow);
}

.theme-toggle svg {
  width: 18px;
  height: 18px;
}

/* Mobile nav toggle */
.nav__hamburger {
  display: none;
  background: none;
  border: none;
  cursor: pointer;
  padding: 4px;
  color: var(--text);
}

.nav__hamburger svg {
  width: 24px;
  height: 24px;
}

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

  .nav__links {
    display: none;
    position: absolute;
    top: 60px;
    left: 0;
    right: 0;
    flex-direction: column;
    background: var(--nav-bg);
    backdrop-filter: blur(16px);
    -webkit-backdrop-filter: blur(16px);
    border-bottom: 1px solid var(--border);
    padding: 16px 24px;
    gap: 16px;
  }

  .nav__links.open {
    display: flex;
  }
}

/* ===== Hero ===== */
.hero {
  min-height: 85vh;
  display: flex;
  align-items: center;
  padding-top: 60px;
  position: relative;
  overflow: hidden;
}

.hero::before {
  content: "";
  position: absolute;
  inset: 0;
  background: radial-gradient(ellipse at 70% 40%, var(--accent-glow) 0%, transparent 55%);
  pointer-events: none;
}

.hero__inner {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 48px;
  width: 100%;
}

.hero__content {
  flex: 1;
  max-width: 560px;
}

.hero__name {
  font-size: clamp(2.5rem, 5vw, 4rem);
  font-weight: 800;
  letter-spacing: -0.04em;
  margin-bottom: 16px;
  background: linear-gradient(135deg, var(--text) 0%, var(--accent) 100%);
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
  background-clip: text;
  animation: heroFadeUp 0.7s ease both;
}

.hero__tagline {
  font-size: 1.2rem;
  color: var(--text-secondary);
  margin-bottom: 32px;
  line-height: 1.6;
  animation: heroFadeUp 0.7s ease 0.15s both;
}

.hero__links {
  display: flex;
  flex-wrap: wrap;
  gap: 12px;
  list-style: none;
  margin: 0;
  padding: 0;
  animation: heroFadeUp 0.7s ease 0.3s both;
}

.hero__links li {
  margin: 0;
  padding: 0;
}

.hero__social {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  width: 44px;
  height: 44px;
  border: 1px solid var(--border);
  border-radius: 12px;
  color: var(--text-secondary);
  transition: border-color var(--transition), color var(--transition), transform 0.2s ease, background-color var(--transition);
}

.hero__social:hover {
  border-color: var(--accent);
  color: var(--accent);
  transform: translateY(-2px);
  background: var(--accent-glow);
}

.hero__social svg {
  width: 20px;
  height: 20px;
}

.hero__photo {
  flex-shrink: 0;
  animation: heroFadeIn 0.8s ease 0.3s both;
}

.hero__photo img {
  width: 300px;
  height: 360px;
  object-fit: cover;
  border-radius: 20px;
  border: 1px solid var(--border);
  transition: border-color var(--transition);
}

/* ===== About ===== */
.about__content {
  max-width: 700px;
  margin: 0 auto;
  color: var(--text-secondary);
  font-size: 1.1rem;
  line-height: 1.8;
}

/* ===== Projects ===== */
.filter-bar {
  display: flex;
  flex-wrap: wrap;
  gap: 8px;
  margin-bottom: 32px;
}

.filter-btn {
  padding: 6px 16px;
  border: 1px solid var(--border);
  border-radius: 20px;
  background: transparent;
  color: var(--text-secondary);
  font-family: var(--font-heading);
  font-size: 0.82rem;
  font-weight: 500;
  cursor: pointer;
  transition: all var(--transition);
}

.filter-btn:hover {
  border-color: var(--accent);
  color: var(--accent);
  background: var(--accent-glow);
}

.filter-btn.active {
  background: var(--tag-active-bg);
  color: var(--tag-active-text);
  border-color: var(--tag-active-bg);
}

.projects-grid {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(300px, 1fr));
  gap: 20px;
}

.project-card {
  background: var(--card-bg);
  border: 1px solid var(--border);
  border-radius: 16px;
  padding: 24px;
  transition: border-color var(--transition), box-shadow var(--transition), transform 0.2s ease;
}

.project-card:hover {
  border-color: var(--accent);
  box-shadow: var(--card-shadow-hover);
  transform: translateY(-3px);
}

.project-card.hidden {
  display: none;
}

.project-card__title {
  font-family: var(--font-heading);
  font-size: 1.15rem;
  font-weight: 600;
  margin-bottom: 8px;
  letter-spacing: -0.01em;
}

.project-card__desc {
  color: var(--text-secondary);
  font-size: 0.9rem;
  margin-bottom: 16px;
  line-height: 1.55;
}

.project-card__tags {
  display: flex;
  flex-wrap: wrap;
  gap: 6px;
  margin-bottom: 16px;
}

.project-card__tag {
  padding: 3px 10px;
  border-radius: 20px;
  background: var(--tag-bg);
  color: var(--tag-text);
  font-family: var(--font-heading);
  font-size: 0.72rem;
  font-weight: 600;
  letter-spacing: 0.01em;
}

.project-card__links {
  display: flex;
  gap: 12px;
}

.project-card__links a {
  font-size: 0.85rem;
  font-weight: 500;
}

/* ===== Timeline ===== */
.timeline {
  position: relative;
  max-width: 700px;
  margin: 0 auto;
  padding-left: 36px;
}

.timeline::before {
  content: "";
  position: absolute;
  left: 7px;
  top: 0;
  bottom: 0;
  width: 2px;
  background: linear-gradient(to bottom, var(--accent) 0%, var(--timeline-line) 40%, transparent 100%);
}

.timeline__item {
  position: relative;
  margin-bottom: 36px;
  padding: 20px 24px;
  background: var(--card-bg);
  border: 1px solid var(--border);
  border-radius: 14px;
  transition: border-color var(--transition), box-shadow var(--transition);
}

.timeline__item:hover {
  border-color: var(--accent);
  box-shadow: var(--card-shadow-hover);
}

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

.timeline__item:first-child .timeline__dot {
  box-shadow: 0 0 0 4px var(--accent-glow);
}

.timeline__dot {
  position: absolute;
  left: -36px;
  top: 24px;
  width: 16px;
  height: 16px;
  border-radius: 50%;
  background: var(--timeline-dot);
  border: 3px solid var(--bg);
  transition: background-color var(--transition), border-color var(--transition), box-shadow var(--transition);
}

.timeline__date {
  font-family: var(--font-heading);
  font-size: 0.78rem;
  color: var(--accent);
  font-weight: 600;
  margin-bottom: 4px;
  letter-spacing: 0.01em;
}

.timeline__role {
  font-family: var(--font-heading);
  font-size: 1.1rem;
  font-weight: 700;
  margin-bottom: 2px;
  letter-spacing: -0.01em;
}

.timeline__org {
  font-size: 0.9rem;
  color: var(--text-secondary);
  margin-bottom: 8px;
}

.timeline__desc {
  font-size: 0.9rem;
  color: var(--text-secondary);
  line-height: 1.6;
}

/* ===== Footer ===== */
.footer {
  position: relative;
  padding: 48px 0;
  text-align: center;
  color: var(--text-secondary);
  font-size: 0.85rem;
}

.footer::before {
  content: "";
  position: absolute;
  top: 0;
  left: 50%;
  transform: translateX(-50%);
  width: 200px;
  height: 1px;
  background: linear-gradient(90deg, transparent, var(--border), transparent);
}

.footer__links {
  display: flex;
  justify-content: center;
  gap: 20px;
  margin-bottom: 16px;
}

.footer__links a {
  color: var(--text-secondary);
  transition: color var(--transition), transform 0.2s ease;
  display: inline-flex;
}

.footer__links a:hover {
  color: var(--accent);
  transform: translateY(-2px);
}

.footer__links svg {
  width: 20px;
  height: 20px;
}

/* ===== Scroll 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);
}

.fade-in.visible .project-card,
.fade-in.visible .timeline__item,
.fade-in.visible .feed-item {
  animation: staggerFadeUp 0.5s ease both;
}

/* ===== Project Sub-Pages ===== */
.page-header {
  padding: 80px 0 40px;
  border-bottom: 1px solid var(--border);
  margin-bottom: 40px;
}

.page-header__back {
  display: inline-flex;
  align-items: center;
  gap: 4px;
  font-size: 0.85rem;
  color: var(--text-secondary);
  margin-bottom: 16px;
}

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

.page-content {
  max-width: 700px;
  margin: 0 auto;
  padding-bottom: 80px;
  line-height: 1.8;
  color: var(--text-secondary);
}

.page-content h2 {
  color: var(--text);
  margin: 32px 0 12px;
  font-size: 1.3rem;
}

.page-content h3 {
  color: var(--text);
  margin: 24px 0 8px;
}

.page-content p {
  margin-bottom: 16px;
}

.page-content ul {
  margin: 0 0 16px 20px;
}

.page-content li {
  margin-bottom: 8px;
}

/* ===== 404 ===== */
.not-found {
  min-height: 100vh;
  display: flex;
  flex-direction: column;
  align-items: center;
  justify-content: center;
  text-align: center;
}

.not-found__code {
  font-family: var(--font-heading);
  font-size: 6rem;
  font-weight: 800;
  color: var(--accent);
  line-height: 1;
  margin-bottom: 8px;
}

.not-found__msg {
  color: var(--text-secondary);
  margin-bottom: 24px;
}

.not-found__link {
  padding: 10px 24px;
  border: 1px solid var(--accent);
  border-radius: 8px;
  font-weight: 500;
}

/* ===== Feed ===== */
.feed-list {
  display: flex;
  flex-direction: column;
  gap: 16px;
  max-width: 700px;
  margin: 0 auto;
}

.feed-item {
  background: var(--card-bg);
  border: 1px solid var(--border);
  border-radius: 14px;
  padding: 20px 24px;
  transition: border-color var(--transition), box-shadow var(--transition), transform 0.2s ease;
}

.feed-item:hover {
  border-color: var(--accent);
  box-shadow: var(--card-shadow-hover);
  transform: translateY(-2px);
}

.feed-item.hidden {
  display: none;
}

.feed-item__header {
  display: flex;
  align-items: center;
  gap: 10px;
  margin-bottom: 6px;
}

.feed-item__type {
  display: inline-block;
  padding: 2px 8px;
  border-radius: 10px;
  font-family: var(--font-heading);
  font-size: 0.7rem;
  font-weight: 600;
  text-transform: uppercase;
  letter-spacing: 0.03em;
}

.feed-item__type--medium {
  background: #00ab6c18;
  color: #00ab6c;
}

[data-theme="dark"] .feed-item__type--medium {
  background: #00ab6c25;
  color: #2dd98e;
}

.feed-item__type--linkedin {
  background: #0a66c218;
  color: #0a66c2;
}

[data-theme="dark"] .feed-item__type--linkedin {
  background: #0a66c225;
  color: #5da3e8;
}

.feed-item__type--news {
  background: var(--tag-bg);
  color: var(--text-secondary);
}

.feed-item__type--post {
  background: var(--tag-bg);
  color: var(--accent);
}

.feed-item__type--talk {
  background: #f59e0b18;
  color: #d97706;
}

[data-theme="dark"] .feed-item__type--talk {
  background: #f59e0b20;
  color: #fbbf24;
}

.feed-item__type--podcast {
  background: #ec489918;
  color: #db2777;
}

[data-theme="dark"] .feed-item__type--podcast {
  background: #ec489920;
  color: #f472b6;
}

.feed-item__type--video {
  background: #ef444418;
  color: #dc2626;
}

[data-theme="dark"] .feed-item__type--video {
  background: #ef444420;
  color: #f87171;
}

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

.feed-item__title {
  font-family: var(--font-heading);
  font-size: 1.05rem;
  font-weight: 600;
  margin-bottom: 4px;
  letter-spacing: -0.01em;
}

.feed-item__title a {
  color: var(--text);
}

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

.feed-item__desc {
  font-size: 0.9rem;
  color: var(--text-secondary);
  line-height: 1.55;
}

.feed-item__read-toggle {
  display: inline-block;
  margin-top: 10px;
  font-size: 0.85rem;
  font-weight: 500;
  color: var(--accent);
  cursor: pointer;
  background: none;
  border: none;
  padding: 0;
}

.feed-item__read-toggle:hover {
  color: var(--accent-hover);
}

.feed-item__body {
  display: none;
  margin-top: 16px;
  padding-top: 16px;
  border-top: 1px solid var(--border);
  line-height: 1.8;
  color: var(--text-secondary);
}

.feed-item__body.open {
  display: block;
}

.feed-item__body p {
  margin-bottom: 12px;
}

.feed-view-all {
  display: inline-block;
  font-size: 0.95rem;
  font-weight: 500;
  color: var(--accent);
}

.feed-view-all:hover {
  color: var(--accent-hover);
}

/* Feed page header */
.feed-page-header {
  padding-top: 100px;
  padding-bottom: 40px;
}

/* ===== Responsive ===== */
@media (max-width: 768px) {
  h1 { font-size: 2rem; }

  section { padding: 48px 0; }

  .hero {
    min-height: auto;
    padding-top: 100px;
    padding-bottom: 48px;
  }

  .hero__inner {
    flex-direction: column-reverse;
    text-align: center;
    gap: 32px;
  }

  .hero__content {
    max-width: 100%;
  }

  .hero__name {
    font-size: 2.5rem;
  }

  .hero__links {
    justify-content: center;
  }

  .hero__photo img {
    width: 200px;
    height: 240px;
  }

  .section-title::before {
    margin-left: auto;
    margin-right: auto;
  }

  .section-title {
    text-align: center;
  }

  .about__content {
    text-align: center;
  }

  .filter-bar {
    justify-content: center;
  }

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