/* ===== CSS Custom Properties ===== */
:root {
  --color-text: #334155;
  --color-text-secondary: #64748b;
  --color-heading: #1e293b;
  --color-accent: #5b7e91;
  --color-accent-hover: #4a6a7a;
  --color-glass-bg: rgba(250, 250, 248, 0.9);
  --color-glass-blur: 12px;
  --color-border: rgba(0, 0, 0, 0.08);
  --color-bg-subtle: rgba(0, 0, 0, 0.02);
  --font-heading: 'Georgia', 'Noto Serif SC', 'Source Han Serif SC', 'SimSun', serif;
  --font-body: 'Inter', -apple-system, BlinkMacSystemFont, 'Noto Sans SC', 'PingFang SC', 'Microsoft YaHei', sans-serif;
  --font-mono: 'Fira Code', 'Cascadia Code', 'Consolas', monospace;
  --content-max-width: 700px;
  --sidebar-width: 280px;
  --layout-max-width: 1200px;
  --line-height: 1.8;
}

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

html { scroll-behavior: smooth; }

body {
  font-family: var(--font-body);
  color: var(--color-text);
  line-height: var(--line-height);
  font-size: 16px;
  letter-spacing: 0.02em;
  -webkit-font-smoothing: antialiased;
}

a {
  color: var(--color-accent);
  text-decoration: none;
  transition: color 0.2s;
}
a:hover { color: var(--color-accent-hover); }

img { max-width: 100%; height: auto; border-radius: 4px; }

/* ===== Top Navigation Bar ===== */
.top-nav {
  position: fixed;
  top: 0; left: 0; right: 0;
  z-index: 50;
  display: flex;
  justify-content: flex-end;
  align-items: center;
  padding: 16px 40px;
  gap: 28px;
  transition: background 0.3s, transform 0.3s;
}

.top-nav.nav-hidden {
  transform: translateY(-100%);
}

.top-nav.scrolled {
  background: rgba(250, 250, 248, 0.85);
  backdrop-filter: blur(10px);
  -webkit-backdrop-filter: blur(10px);
  box-shadow: 0 1px 0 var(--color-border);
}

.top-nav a {
  font-family: var(--font-body);
  font-size: 0.9rem;
  font-weight: 500;
  color: #fff;
  text-shadow: 0 1px 6px rgba(0, 0, 0, 0.4);
  transition: color 0.3s, text-shadow 0.3s;
}

.top-nav.scrolled a {
  color: var(--color-text);
  text-shadow: none;
}

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

/* ===== Fixed Parallax Background ===== */
.bg-layer {
  position: fixed;
  top: 0; left: 0;
  width: 100%; height: 100%;
  background-size: cover;
  background-position: center;
  background-repeat: no-repeat;
  z-index: -1;
}

/* Dark overlay for contrast with white text */
.bg-layer::after {
  content: '';
  position: absolute;
  top: 0; left: 0;
  width: 100%; height: 100%;
  background: rgba(0, 0, 0, 0.18);
}

/* ===== Hero Section ===== */
.hero {
  height: 100vh;
  display: flex;
  flex-direction: column;
  align-items: center;
  justify-content: center;
  text-align: center;
  color: #fff;
  padding: 0 20px;
}

.hero h1 {
  font-family: var(--font-heading);
  font-size: 3.2rem;
  font-weight: 700;
  letter-spacing: 0.03em;
  margin-bottom: 0.4em;
  text-shadow: 0 2px 20px rgba(0, 0, 0, 0.5), 0 1px 3px rgba(0, 0, 0, 0.3);
}

.hero .tagline {
  font-size: 1.15rem;
  font-weight: 400;
  opacity: 0.95;
  text-shadow: 0 1px 8px rgba(0, 0, 0, 0.4);
}

.hero .scroll-hint {
  position: absolute;
  bottom: 40px;
  font-size: 0.85rem;
  opacity: 0.7;
  text-shadow: 0 1px 4px rgba(0, 0, 0, 0.3);
  animation: float 2s ease-in-out infinite;
}

@keyframes float {
  0%, 100% { transform: translateY(0); }
  50% { transform: translateY(-8px); }
}

/* ===== Glassmorphism Container ===== */
.glass-container {
  position: relative;
  max-width: var(--layout-max-width);
  margin: 40px auto 60px;
  margin-left: 5%;
  margin-right: 5%;
  padding: 48px;
  background: rgba(252, 251, 249, 0.95);
  border-radius: 12px;
  min-height: 60vh;
  /* Use will-change to promote to own layer, avoiding backdrop-filter jank */
  will-change: transform;
}

@media (min-width: 1350px) {
  .glass-container {
    margin-left: auto;
    margin-right: auto;
  }
}

/* ===== Two-Column Layout ===== */
.layout-flex {
  display: flex;
  gap: 80px;
}

/* ===== Sidebar (right side) ===== */
.sidebar {
  width: var(--sidebar-width);
  flex-shrink: 0;
  position: sticky;
  top: 70px; /* clear the fixed top nav (~50px) */
  align-self: flex-start;
  order: 2;
  margin-top: 60px; /* sink below post title area */
}

.sidebar-avatar {
  width: 80px;
  height: 80px;
  border-radius: 50%;
  margin-bottom: 12px;
}

.sidebar-name {
  font-family: var(--font-heading);
  font-size: 1.25rem;
  font-weight: 700;
  margin-bottom: 4px;
}

.sidebar-bio {
  font-size: 0.85rem;
  color: var(--color-text-secondary);
  margin-bottom: 24px;
  line-height: 1.5;
}

/* Sidebar sections */
.sidebar-section {
  margin-bottom: 24px;
}

.sidebar-section-title {
  font-family: var(--font-heading);
  font-size: 0.9rem;
  font-weight: 700;
  text-transform: uppercase;
  letter-spacing: 0.06em;
  color: var(--color-text);
  margin-bottom: 10px;
  padding-bottom: 6px;
  border-bottom: 2px solid var(--color-text);
}

.sidebar-list {
  list-style: none;
}

.sidebar-list li {
  padding: 3px 0;
}

.sidebar-list a {
  font-size: 0.88rem;
  color: var(--color-text-secondary);
  display: flex;
  justify-content: space-between;
  align-items: baseline;
}

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

.sidebar-list .count {
  font-size: 0.78rem;
  color: var(--color-text-secondary);
  opacity: 0.6;
}

/* Hamburger button — hidden on desktop */
.hamburger {
  display: none;
  background: none;
  border: none;
  font-size: 1.5rem;
  cursor: pointer;
  color: var(--color-text);
  padding: 8px;
}

/* ===== Main Content ===== */
.content {
  flex: 1;
  min-width: 0;
  max-width: var(--content-max-width);
  order: 1;
}

/* ===== Post List (Homepage) ===== */
.post-list { list-style: none; }

.post-list li {
  padding: 18px 0;
  border-bottom: 1px solid var(--color-border);
}

.post-list li:last-child { border-bottom: none; }

.post-list .post-date {
  font-size: 0.82rem;
  color: var(--color-text-secondary);
  font-variant-numeric: tabular-nums;
}

.post-list .post-title {
  font-family: var(--font-heading);
  font-size: 1.15rem;
  font-weight: 700;
  margin-top: 2px;
}

.post-list .post-title a { color: var(--color-text); }
.post-list .post-title a:hover { color: var(--color-accent); }

.post-list .post-desc {
  font-size: 0.9rem;
  color: var(--color-text-secondary);
  margin-top: 4px;
}

/* ===== Post Page ===== */
.post-header {
  margin-bottom: 32px;
  padding-bottom: 16px;
  border-bottom: 2px solid var(--color-text);
}

.post-header h1 {
  font-family: var(--font-heading);
  font-size: 2rem;
  font-weight: 700;
  line-height: 1.3;
  margin-bottom: 8px;
  color: var(--color-heading);
}

.post-meta {
  font-size: 0.85rem;
  color: var(--color-text-secondary);
}

.post-meta .tag {
  display: inline-block;
  background: var(--color-bg-subtle);
  border: 1px solid var(--color-border);
  border-radius: 3px;
  padding: 1px 8px;
  margin-right: 4px;
  font-size: 0.8rem;
}

/* ===== Post Body Typography ===== */
.post-body h1, .post-body h2, .post-body h3, .post-body h4 {
  font-family: var(--font-heading);
  color: var(--color-heading);
  margin-top: 1.6em;
  margin-bottom: 0.6em;
  font-weight: 700;
}

.post-body h1 { font-size: 1.5rem; }
.post-body h2 {
  font-size: 1.35rem;
  margin-top: 2.5em;
  margin-bottom: 1em;
  padding-bottom: 0.4em;
  border-bottom: 1px solid rgba(107, 114, 128, 0.2);
}
.post-body h3 { font-size: 1.15rem; }
.post-body h4 { font-size: 1.05rem; }

.post-body p {
  margin-bottom: 2em;
}

.post-body ul, .post-body ol {
  margin-bottom: 1em;
  padding-left: 1.5em;
}

.post-body li { margin-bottom: 0.3em; }

.post-body blockquote {
  border-left: 3px solid var(--color-accent);
  padding: 8px 16px;
  margin: 1em 0;
  color: var(--color-text-secondary);
  background: var(--color-bg-subtle);
  border-radius: 0 4px 4px 0;
}

.post-body code {
  font-family: var(--font-mono);
  font-size: 0.88em;
  background: var(--color-bg-subtle);
  border: 1px solid var(--color-border);
  border-radius: 3px;
  padding: 1px 5px;
}

.post-body pre {
  margin: 1em 0;
  border-radius: 6px;
  overflow-x: auto;
  background: #f6f8fa;
  border: 1px solid var(--color-border);
}

.post-body pre code {
  display: block;
  padding: 16px;
  background: none;
  border: none;
  font-size: 0.85rem;
  line-height: 1.6;
}

.post-body table {
  width: 100%;
  border-collapse: collapse;
  margin: 1em 0;
  font-size: 0.9rem;
}

.post-body th, .post-body td {
  border: 1px solid var(--color-border);
  padding: 8px 12px;
  text-align: left;
}

.post-body th {
  background: var(--color-bg-subtle);
  font-weight: 700;
}

.post-body img {
  display: block;
  margin: 1em auto;
}

/* ===== Archives Page ===== */
.archive-year {
  font-family: var(--font-heading);
  font-size: 1.4rem;
  font-weight: 700;
  margin-top: 2em;
  margin-bottom: 0.6em;
}

.archive-year:first-child { margin-top: 0; }

.archive-list { list-style: none; }

.archive-list li {
  padding: 8px 0;
  display: flex;
  gap: 16px;
  align-items: baseline;
}

.archive-list .date {
  font-size: 0.85rem;
  color: var(--color-text-secondary);
  flex-shrink: 0;
  font-variant-numeric: tabular-nums;
}

/* ===== Tags Page ===== */
.tag-cloud {
  display: flex;
  flex-wrap: wrap;
  gap: 8px;
  margin-bottom: 32px;
}

.tag-cloud a {
  display: inline-block;
  background: var(--color-bg-subtle);
  border: 1px solid var(--color-border);
  border-radius: 4px;
  padding: 4px 12px;
  font-size: 0.9rem;
  transition: background 0.2s, border-color 0.2s;
}

.tag-cloud a:hover,
.tag-cloud a.active {
  background: var(--color-accent);
  border-color: var(--color-accent);
  color: #fff;
}

.tag-cloud .count {
  font-size: 0.8rem;
  color: var(--color-text-secondary);
  margin-left: 4px;
}

/* ===== Page Title ===== */
.page-title {
  font-family: var(--font-heading);
  font-size: 1.6rem;
  font-weight: 700;
  margin-bottom: 24px;
  color: var(--color-heading);
}

/* ===== Footer ===== */
.site-footer {
  text-align: center;
  padding: 24px 20px;
  font-size: 0.8rem;
  color: rgba(255, 255, 255, 0.7);
  text-shadow: 0 1px 4px rgba(0, 0, 0, 0.3);
}

/* ===== Math ===== */
.math-display {
  overflow-x: auto;
  margin: 1em 0;
}

/* ===== Responsive: Mobile ===== */
@media (max-width: 900px) {
  .top-nav {
    padding: 12px 16px;
    gap: 16px;
  }

  .glass-container {
    margin: 20px 8px 40px;
    padding: 20px 16px;
    border-radius: 8px;
  }

  .layout-flex {
    flex-direction: column;
    gap: 0;
  }

  /* Hamburger nav */
  .hamburger {
    display: block;
    position: fixed;
    top: 12px;
    right: 16px;
    z-index: 100;
    background: var(--color-glass-bg);
    backdrop-filter: blur(8px);
    -webkit-backdrop-filter: blur(8px);
    border-radius: 6px;
    border: 1px solid var(--color-border);
  }

  .sidebar {
    position: fixed;
    top: 0; right: 0;
    width: 280px;
    height: 100vh;
    background: var(--color-glass-bg);
    backdrop-filter: blur(16px);
    -webkit-backdrop-filter: blur(16px);
    padding: 60px 24px 24px;
    z-index: 99;
    transform: translateX(100%);
    transition: transform 0.3s ease;
    overflow-y: auto;
    border-radius: 0;
  }

  .sidebar.sidebar-open {
    transform: translateX(0);
  }

  .sidebar-overlay {
    display: none;
    position: fixed;
    top: 0; left: 0;
    width: 100%; height: 100%;
    background: rgba(0, 0, 0, 0.3);
    z-index: 98;
  }

  .sidebar-overlay.active { display: block; }

  .content {
    max-width: 100%;
  }

  .hero h1 { font-size: 2.2rem; }
}