:root {
  --color-bg: #f9f9f9;
  --color-surface: #ffffff;
  --color-surface-soft: #f4f4f5;
  --color-text-main: #111111;
  --color-text-secondary: #4b5563;
  --color-text-muted: #6b7280;
  --color-border: #e5e7eb;
  --color-border-hover: #d1d5db;
  --color-accent: #111111;
  --color-mark-bg: #fef08a;
  --color-mark-text: #111111;

  --font-serif: 'Cardo', 'Iowan Old Style', 'Palatino Linotype', 'Songti SC', 'STSong', Georgia, serif;
  --font-mono: 'Maple Mono NF CN', ui-monospace, SFMono-Regular, Menlo, Monaco, Consolas, monospace;
  --font-sans: 'Inter', -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, "PingFang SC", "Hiragino Sans GB", "Microsoft YaHei", sans-serif;

  --max-width: 1180px;
  --content-width: 820px;
  --header-height: 64px;

  --radius-sm: 6px;
  --radius-md: 12px;
  --radius-lg: 20px;
  --radius-full: 9999px;

  --transition-fast: 0.15s ease;
  --transition-normal: 0.25s ease;
}

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

html {
  font-size: 16px;
  scroll-behavior: smooth;
  scroll-padding-top: calc(var(--header-height) + 1.5rem);
  -webkit-text-size-adjust: 100%;
}

/* Ensure hash navigation (#) and footnotes never hide under sticky header */
:target,
[id],
h1[id], h2[id], h3[id], h4[id], h5[id], h6[id],
.footnote-ref,
.footnote-item,
li[id^="fn"] {
  scroll-margin-top: calc(var(--header-height) + 1.5rem);
}

/* Responsive media constraint - never wider than parent container */
img, video, iframe, embed, object {
  max-width: 100%;
  height: auto;
}

body {
  font-family: var(--font-serif);
  color: var(--color-text-main);
  background-color: var(--color-bg);
  line-height: 1.8;
  letter-spacing: 0.01em;
  min-height: 100vh;
  display: flex;
  flex-direction: column;
}

.container {
  width: 100%;
  max-width: var(--max-width);
  margin: 0 auto;
  padding: 0 2rem;
}

.content-container {
  width: 100%;
  max-width: var(--content-width);
  margin: 0 auto;
}

/* Header */
.site-header {
  position: sticky;
  top: 0;
  z-index: 100;
  background: rgba(249, 249, 249, 0.95);
  backdrop-filter: blur(10px);
  -webkit-backdrop-filter: blur(10px);
  height: var(--header-height);
  display: flex;
  align-items: center;
}

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

.brand {
  text-decoration: none;
  color: var(--color-text-main);
}

.brand-title {
  font-size: 1.55rem;
  font-family: var(--font-serif);
  font-weight: 700;
  letter-spacing: -0.01em;
}

.site-nav {
  display: flex;
  gap: 2rem;
  align-items: center;
}

.nav-link {
  text-decoration: none;
  font-family: var(--font-serif);
  font-size: 1.05rem;
  color: var(--color-text-main);
  transition: opacity var(--transition-fast);
  padding: 0.25rem 0;
}

.nav-link:hover {
  opacity: 0.65;
}

.nav-link.active {
  text-decoration: underline;
  text-underline-offset: 4px;
}

/* Mobile Hamburger Menu Toggle */
.mobile-menu-toggle {
  display: none;
  background: none;
  border: none;
  cursor: pointer;
  padding: 0.5rem;
  flex-direction: column;
  justify-content: center;
  gap: 5px;
  width: 40px;
  height: 40px;
}

.hamburger-line {
  display: block;
  width: 22px;
  height: 2px;
  background-color: var(--color-text-main);
  border-radius: 2px;
  transition: transform 0.25s ease, opacity 0.25s ease;
}

.mobile-menu-toggle.is-active .hamburger-line:nth-child(1) {
  transform: translateY(7px) rotate(45deg);
}

.mobile-menu-toggle.is-active .hamburger-line:nth-child(2) {
  opacity: 0;
}

.mobile-menu-toggle.is-active .hamburger-line:nth-child(3) {
  transform: translateY(-7px) rotate(-45deg);
}

/* Mobile Slide-Down Navigation Drawer */
.mobile-nav-drawer {
  display: none;
  position: absolute;
  top: 100%;
  left: 0;
  width: 100%;
  background: var(--color-bg);
  border-bottom: 1px solid var(--color-border);
  box-shadow: 0 8px 24px rgba(0, 0, 0, 0.08);
  padding: 0.75rem 1.25rem 1.25rem;
  z-index: 999;
}

.mobile-nav-drawer.is-open {
  display: block;
  animation: slideDown 0.25s ease;
}

@keyframes slideDown {
  from { opacity: 0; transform: translateY(-8px); }
  to { opacity: 1; transform: translateY(0); }
}

.mobile-nav-links {
  display: flex;
  flex-direction: column;
}

.mobile-nav-link {
  display: flex;
  justify-content: space-between;
  align-items: center;
  padding: 0.85rem 0.5rem;
  text-decoration: none;
  color: var(--color-text-main);
  font-family: var(--font-serif);
  font-size: 1.15rem;
  border-bottom: 1px solid var(--color-border-subtle, rgba(0, 0, 0, 0.05));
  transition: color var(--transition-fast), padding-left var(--transition-fast);
}

.mobile-nav-link:last-child {
  border-bottom: none;
}

.mobile-nav-link:hover, .mobile-nav-link:active {
  color: var(--color-accent);
  padding-left: 0.75rem;
}

.mobile-nav-link.active {
  font-weight: 600;
  color: var(--color-accent);
}

.mobile-nav-arrow {
  font-size: 1rem;
  opacity: 0.4;
}

/* Main Content area */
.site-main {
  flex: 1;
  padding: 2.5rem 0 4rem;
}

/* Footer */
.site-footer {
  border-top: 1px solid var(--color-border);
  background-color: var(--color-surface);
  padding: 2.5rem 0;
  font-family: var(--font-sans);
  font-size: 0.88rem;
  color: var(--color-text-muted);
}

.footer-inner {
  display: flex;
  justify-content: space-between;
  align-items: center;
  flex-wrap: wrap;
  gap: 1.5rem;
}

.social-links {
  display: flex;
  gap: 1.25rem;
  align-items: center;
}

.social-link {
  color: var(--color-text-secondary);
  display: flex;
  align-items: center;
  justify-content: center;
  transition: color var(--transition-fast), transform var(--transition-fast);
}

.social-link:hover {
  color: var(--color-text-main);
  transform: translateY(-2px);
}

.social-link svg {
  width: 19px;
  height: 19px;
  fill: currentColor;
}

/* Headings & Typography */
h1, h2, h3, h4, h5, h6 {
  color: var(--color-text-main);
  line-height: 1.35;
  margin-bottom: 1rem;
  font-weight: 700;
}

h1 { font-size: 2.2rem; }
h2 { font-size: 1.65rem; margin-top: 2rem; }
h3 { font-size: 1.35rem; margin-top: 1.5rem; }

p {
  margin-bottom: 1.25rem;
}

a {
  color: var(--color-accent);
  text-decoration: underline;
  text-decoration-thickness: 1px;
  text-underline-offset: 3px;
  transition: color var(--transition-fast);
}

a:hover {
  color: #000000;
}

mark {
  background-color: var(--color-mark-bg);
  color: var(--color-mark-text);
  padding: 0.1em 0.25em;
  border-radius: 3px;
  font-weight: 500;
}

blockquote {
  border-left: 3px solid var(--color-border-hover);
  padding: 0.5rem 0 0.5rem 1.25rem;
  margin: 1.5rem 0;
  color: var(--color-text-secondary);
  font-style: italic;
}

hr {
  border: 0;
  height: 1px;
  background: var(--color-border);
  margin: 2.5rem 0;
}

/* Responsive */
@media (max-width: 768px) {
  :root {
    --header-height: 64px;
    --content-padding: 1.25rem;
  }

  .site-header {
    position: sticky;
    top: 0;
    z-index: 990;
  }

  /* Hide inline desktop nav and show hamburger */
  .site-nav.desktop-nav {
    display: none;
  }

  .mobile-menu-toggle {
    display: flex;
  }

  .brand-title {
    font-size: 1.25rem;
  }

  .brand-tagline {
    font-size: 0.68rem;
    display: block;
    margin-top: 0.1rem;
    opacity: 0.85;
  }

  /* Centered, balanced editorial mobile footer */
  .site-footer {
    padding: 2.5rem 1.25rem 3rem;
  }

  .footer-inner {
    flex-direction: column;
    align-items: center;
    text-align: center;
    gap: 1.4rem;
  }

  .footer-left {
    display: flex;
    flex-direction: column;
    align-items: center;
    gap: 0.45rem;
  }

  .footer-tagline {
    font-family: var(--font-serif);
    font-size: 1.05rem;
    color: var(--color-text-main);
  }

  .footer-copyright {
    font-size: 0.82rem;
    color: var(--color-text-muted);
  }

  .social-links {
    justify-content: center;
    gap: 1.5rem;
  }

  .social-link {
    display: flex;
    align-items: center;
    justify-content: center;
    min-width: 44px;
    min-height: 44px;
  }
}