/* ===== CSS Custom Properties ===== */
:root {
  --color-bg: #fafafa;
  --color-surface: #ffffff;
  --color-text: #1a1a1a;
  --color-text-secondary: #666666;
  --color-accent: #2563eb;
  --color-accent-hover: #1d4ed8;
  --color-border: #e5e5e5;
  --color-code-bg: #f4f4f5;
  --color-shadow: rgba(0, 0, 0, 0.06);
  --color-shadow-hover: rgba(0, 0, 0, 0.12);
  --font-sans: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, "Helvetica Neue", Arial, sans-serif;
  --font-serif: Georgia, "Times New Roman", serif;
  --font-mono: "JetBrains Mono", "Fira Code", "SF Mono", Menlo, monospace;
  --max-width: 720px;
  --space-xs: 0.25rem;
  --space-sm: 0.5rem;
  --space-md: 1rem;
  --space-lg: 2rem;
  --space-xl: 4rem;
  --radius: 8px;
}

[data-theme="dark"] {
  --color-bg: #0d0d0d;
  --color-surface: #161616;
  --color-text: #e8e8e8;
  --color-text-secondary: #999999;
  --color-accent: #60a5fa;
  --color-accent-hover: #93c5fd;
  --color-border: #252525;
  --color-code-bg: #1e1e1e;
  --color-shadow: rgba(0, 0, 0, 0.3);
  --color-shadow-hover: rgba(0, 0, 0, 0.5);
}

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

html {
  font-size: 16px;
  scroll-behavior: smooth;
  -webkit-font-smoothing: antialiased;
  -moz-osx-font-smoothing: grayscale;
}

body {
  font-family: var(--font-sans);
  line-height: 1.7;
  color: var(--color-text);
  background-color: var(--color-bg);
  transition: background-color 0.3s ease, color 0.3s ease;
}

a {
  color: var(--color-accent);
  text-decoration: none;
  text-underline-offset: 3px;
}

a:hover {
  text-decoration: underline;
}

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

/* ===== Navigation ===== */
.site-nav {
  position: fixed;
  top: 0;
  left: 0;
  right: 0;
  z-index: 100;
  padding: var(--space-md) var(--space-lg);
  display: flex;
  justify-content: space-between;
  align-items: center;
  transition: background-color 0.3s ease, box-shadow 0.3s ease;
}

.site-nav.scrolled {
  background-color: var(--color-surface);
  box-shadow: 0 1px 8px var(--color-shadow);
  backdrop-filter: blur(12px);
  -webkit-backdrop-filter: blur(12px);
}

[data-theme="dark"] .site-nav.scrolled {
  background-color: rgba(22, 22, 22, 0.85);
}

.site-nav__inner {
  max-width: var(--max-width);
  margin: 0 auto;
  width: 100%;
  display: flex;
  justify-content: space-between;
  align-items: center;
}

.site-nav__brand {
  font-weight: 700;
  font-size: 1.125rem;
  color: var(--color-text);
  text-decoration: none;
  letter-spacing: -0.02em;
  transition: color 0.15s ease;
}

.site-nav__brand:hover {
  text-decoration: none;
  color: var(--color-accent);
}

.site-nav__links {
  display: flex;
  align-items: center;
  gap: var(--space-lg);
}

.site-nav__links a {
  color: var(--color-text-secondary);
  font-size: 0.875rem;
  text-decoration: none;
  transition: color 0.15s ease;
}

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

.theme-toggle {
  background: none;
  border: none;
  color: var(--color-text-secondary);
  cursor: pointer;
  padding: var(--space-xs);
  display: flex;
  align-items: center;
  font-size: 1.125rem;
  transition: color 0.15s ease;
}

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

/* ===== Motto Hero ===== */
.motto {
  height: 100vh;
  display: flex;
  flex-direction: column;
  justify-content: center;
  align-items: center;
  text-align: center;
  padding: var(--space-xl);
  position: relative;
}

.motto__content {
  max-width: 680px;
}

.motto__text {
  font-family: var(--font-serif);
  font-size: 2.75rem;
  font-weight: 400;
  line-height: 1.3;
  letter-spacing: -0.01em;
  color: var(--color-text);
  margin-bottom: var(--space-lg);
}

.motto__author {
  font-family: var(--font-mono);
  font-size: 0.8125rem;
  color: var(--color-text-secondary);
  letter-spacing: 0.05em;
}

.motto__scroll {
  position: absolute;
  bottom: 2.5rem;
  color: var(--color-text-secondary);
  opacity: 0.5;
  transition: opacity 0.3s ease;
  animation: bounce 2s infinite;
}

.motto__scroll:hover {
  opacity: 1;
  text-decoration: none;
}

@keyframes bounce {
  0%, 20%, 50%, 80%, 100% { transform: translateY(0); }
  40% { transform: translateY(-8px); }
  60% { transform: translateY(-4px); }
}

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

/* ===== Cards ===== */
.card {
  background: var(--color-surface);
  border-radius: var(--radius);
  padding: var(--space-lg);
  box-shadow: 0 2px 12px var(--color-shadow);
  transition: box-shadow 0.3s ease, transform 0.3s ease;
}

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

/* ===== Profile Card ===== */
.profile-card {
  margin-bottom: var(--space-xl);
}

.profile-card__header {
  display: flex;
  align-items: center;
  gap: var(--space-lg);
  margin-bottom: var(--space-md);
}

.profile-card__avatar {
  width: 72px;
  height: 72px;
  border-radius: 50%;
  object-fit: cover;
  border: 2px solid var(--color-border);
  transition: transform 0.3s ease;
}

.profile-card__avatar:hover {
  transform: scale(1.05);
}

.profile-card__name {
  font-size: 1.5rem;
  font-weight: 700;
  letter-spacing: -0.02em;
  line-height: 1.2;
  margin-bottom: 2px;
}

.profile-card__name-zh {
  font-size: 0.875rem;
  color: var(--color-text-secondary);
  letter-spacing: 0.05em;
  margin-bottom: 4px;
}

.profile-card__role {
  font-family: var(--font-mono);
  font-size: 0.8125rem;
  color: var(--color-text-secondary);
}

.profile-card__bio {
  font-size: 0.9375rem;
  line-height: 1.7;
  color: var(--color-text-secondary);
  margin-bottom: var(--space-md);
}

.profile-card__links {
  display: flex;
  gap: var(--space-lg);
  font-size: 0.875rem;
}

.profile-card__links a {
  color: var(--color-text-secondary);
  display: inline-flex;
  align-items: center;
  gap: 6px;
  transition: color 0.15s ease;
}

.profile-card__links a svg {
  opacity: 0.5;
  transition: opacity 0.15s ease;
}

.profile-card__links a:hover {
  color: var(--color-accent);
  text-decoration: none;
}

.profile-card__links a:hover svg {
  opacity: 1;
}

/* ===== Section ===== */
.section {
  padding: var(--space-xl) 0 var(--space-lg);
  border-top: 1px solid var(--color-border);
}

.section__label {
  font-family: var(--font-mono);
  font-size: 0.75rem;
  font-weight: 500;
  text-transform: uppercase;
  letter-spacing: 0.1em;
  color: var(--color-text-secondary);
  margin-bottom: var(--space-lg);
}

/* ===== About ===== */
.about__text {
  font-size: 0.9375rem;
  line-height: 1.8;
  color: var(--color-text-secondary);
}

/* ===== Tags ===== */
.tags {
  display: flex;
  flex-wrap: wrap;
  gap: var(--space-sm);
}

.tag {
  font-family: var(--font-mono);
  font-size: 0.75rem;
  color: var(--color-text-secondary);
  background: var(--color-surface);
  border: 1px solid var(--color-border);
  border-radius: 4px;
  padding: var(--space-xs) var(--space-sm);
  transition: all 0.2s ease;
  cursor: default;
}

.tag:hover {
  color: var(--color-accent);
  border-color: var(--color-accent);
  box-shadow: 0 2px 8px var(--color-shadow);
}

/* ===== Publication Card ===== */
.publication-card {
  cursor: default;
}

.publication-card:hover {
  transform: none;
}

.publication-card__title {
  font-weight: 600;
  font-size: 0.9375rem;
  line-height: 1.5;
  margin-bottom: var(--space-xs);
}

.publication-card__venue {
  font-family: var(--font-mono);
  font-size: 0.8125rem;
  color: var(--color-text-secondary);
  display: flex;
  align-items: center;
  gap: var(--space-sm);
}

.publication-card__badge {
  font-size: 0.6875rem;
  font-weight: 600;
  color: var(--color-accent);
  border: 1px solid var(--color-accent);
  border-radius: 3px;
  padding: 1px 6px;
}

/* ===== Project Cards ===== */
.project-card {
  display: block;
  text-decoration: none;
  color: var(--color-text);
  margin-bottom: var(--space-md);
  cursor: pointer;
}

.project-card:hover {
  text-decoration: none;
  transform: translateY(-2px);
}

.project-card__header {
  display: flex;
  justify-content: space-between;
  align-items: baseline;
  margin-bottom: var(--space-xs);
}

.project-card__title {
  font-weight: 600;
  font-size: 1rem;
}

.project-card__year {
  font-family: var(--font-mono);
  font-size: 0.8125rem;
  color: var(--color-text-secondary);
  flex-shrink: 0;
}

.project-card__desc {
  font-size: 0.875rem;
  color: var(--color-text-secondary);
  line-height: 1.6;
}

/* ===== Post List ===== */
.post-item {
  display: flex;
  align-items: baseline;
  gap: var(--space-md);
  padding: var(--space-sm) 0;
}

.post-item__date {
  font-family: var(--font-mono);
  font-size: 0.8125rem;
  color: var(--color-text-secondary);
  flex-shrink: 0;
  min-width: 6rem;
}

.post-item__title {
  color: var(--color-text);
  text-decoration: none;
  font-size: 0.9375rem;
  transition: color 0.15s ease;
}

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

.post-item__category {
  font-family: var(--font-mono);
  font-size: 0.75rem;
  color: var(--color-text-secondary);
  flex-shrink: 0;
}

/* ===== Fade-in Animation ===== */
@keyframes fadeInUp {
  from {
    opacity: 0;
    transform: translateY(24px);
  }
  to {
    opacity: 1;
    transform: translateY(0);
  }
}

.fade-in {
  opacity: 0;
  transform: translateY(24px);
}

.fade-in.visible {
  animation: fadeInUp 0.6s ease forwards;
}

.fade-in:nth-child(2) { animation-delay: 0.1s; }
.fade-in:nth-child(3) { animation-delay: 0.2s; }
.fade-in:nth-child(4) { animation-delay: 0.3s; }
.fade-in:nth-child(5) { animation-delay: 0.4s; }

/* ===== Blog Page ===== */
.page-header {
  padding: var(--space-xl) 0 var(--space-lg);
}

.page-header__title {
  font-size: 2rem;
  font-weight: 700;
  letter-spacing: -0.03em;
}

.category-filters {
  display: flex;
  flex-wrap: wrap;
  gap: var(--space-sm);
  margin-bottom: var(--space-lg);
}

.category-filter {
  font-family: var(--font-mono);
  font-size: 0.75rem;
  color: var(--color-text-secondary);
  background: none;
  border: 1px solid var(--color-border);
  padding: var(--space-xs) var(--space-sm);
  cursor: pointer;
  transition: all 0.15s ease;
}

.category-filter:hover,
.category-filter.active {
  color: var(--color-accent);
  border-color: var(--color-accent);
}

/* ===== Post/Project Content ===== */
.article {
  padding: var(--space-xl) 0;
}

.article__back {
  font-size: 0.875rem;
  color: var(--color-text-secondary);
  margin-bottom: var(--space-lg);
  display: inline-block;
}

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

.article__title {
  font-size: 2rem;
  font-weight: 700;
  letter-spacing: -0.02em;
  line-height: 1.2;
  margin-bottom: var(--space-sm);
}

.article__meta {
  font-family: var(--font-mono);
  font-size: 0.8125rem;
  color: var(--color-text-secondary);
  margin-bottom: var(--space-xl);
  display: flex;
  gap: var(--space-md);
  flex-wrap: wrap;
}

.article__status {
  color: var(--color-accent);
}

/* ===== Prose (markdown content) ===== */
.prose {
  font-size: 1rem;
  line-height: 1.8;
}

.prose h1,
.prose h2,
.prose h3,
.prose h4,
.prose h5,
.prose h6 {
  color: var(--color-text);
  font-weight: 600;
  line-height: 1.3;
  margin-top: 2em;
  margin-bottom: 0.75em;
  letter-spacing: -0.02em;
}

.prose h1 { font-size: 1.75rem; }
.prose h2 {
  font-size: 1.375rem;
  padding-bottom: 0.3em;
  border-bottom: 1px solid var(--color-border);
}
.prose h3 { font-size: 1.125rem; }
.prose h4 { font-size: 1rem; }

.prose p {
  margin-bottom: 1.25em;
  color: var(--color-text);
}

.prose a {
  text-decoration: underline;
  text-underline-offset: 3px;
}

.prose img {
  border-radius: var(--radius);
  margin: var(--space-lg) 0;
}

.prose blockquote {
  border-left: 2px solid var(--color-accent);
  padding-left: var(--space-md);
  margin: var(--space-lg) 0;
  color: var(--color-text-secondary);
}

.prose code {
  font-family: var(--font-mono);
  font-size: 0.875em;
  background-color: var(--color-code-bg);
  padding: 0.15em 0.4em;
  border-radius: 3px;
}

.prose pre {
  background-color: var(--color-code-bg);
  padding: var(--space-md);
  border-radius: var(--radius);
  overflow-x: auto;
  margin: var(--space-lg) 0;
  font-size: 0.875rem;
  line-height: 1.6;
}

.prose pre code {
  background: none;
  padding: 0;
  border-radius: 0;
}

.prose ul,
.prose ol {
  margin: var(--space-md) 0;
  padding-left: 1.5em;
}

.prose li {
  margin-bottom: var(--space-sm);
}

.prose hr {
  border: none;
  border-top: 1px solid var(--color-border);
  margin: var(--space-xl) 0;
}

.prose table {
  width: 100%;
  border-collapse: collapse;
  margin: var(--space-lg) 0;
  font-size: 0.875rem;
}

.prose th,
.prose td {
  padding: var(--space-sm) var(--space-md);
  border: 1px solid var(--color-border);
  text-align: left;
}

.prose th {
  font-weight: 600;
  background-color: var(--color-code-bg);
}

.prose strong {
  font-weight: 600;
}

/* ===== Post Navigation ===== */
.post-nav {
  display: flex;
  justify-content: space-between;
  margin-top: var(--space-xl);
  padding-top: var(--space-lg);
  border-top: 1px solid var(--color-border);
  gap: var(--space-lg);
}

.post-nav__link {
  font-size: 0.875rem;
  color: var(--color-text-secondary);
  text-decoration: none;
  max-width: 50%;
}

.post-nav__link:hover {
  color: var(--color-accent);
}

.post-nav__label {
  font-family: var(--font-mono);
  font-size: 0.75rem;
  color: var(--color-text-secondary);
  margin-bottom: var(--space-xs);
  display: block;
}

.post-nav__title {
  font-weight: 500;
}

.post-nav__next {
  text-align: right;
  margin-left: auto;
}

/* ===== Footer ===== */
.site-footer {
  max-width: var(--max-width);
  margin: 0 auto;
  padding: var(--space-xl) var(--space-lg) var(--space-lg);
  border-top: 1px solid var(--color-border);
  font-size: 0.8125rem;
  color: var(--color-text-secondary);
  font-family: var(--font-mono);
}

/* ===== Responsive ===== */
@media (max-width: 640px) {
  :root {
    --space-lg: 1.25rem;
    --space-xl: 2.5rem;
  }

  .site-nav {
    padding: var(--space-md);
  }

  .container {
    padding: var(--space-lg) var(--space-md);
  }

  .motto__text {
    font-size: 1.75rem;
  }

  .motto__scroll {
    bottom: 1.5rem;
  }

  .profile-card__avatar {
    width: 56px;
    height: 56px;
  }

  .profile-card__name {
    font-size: 1.25rem;
  }

  .article__title,
  .page-header__title {
    font-size: 1.5rem;
  }

  .post-item {
    flex-direction: column;
    gap: var(--space-xs);
  }

  .post-item__date {
    min-width: auto;
  }

  .post-nav {
    flex-direction: column;
  }

  .post-nav__link {
    max-width: 100%;
  }

  .post-nav__next {
    text-align: left;
  }
}