:root {
  /* Colors - Light Theme (default) */
  --bg-color: #f8fafc;
  --surface-color: #ffffff;
  --surface-hover: #f1f5f9;
  --text-color: #0f172a;
  --text-muted: #64748b;
  --border-color: #e2e8f0;
  --primary-color: #2563eb;
  --primary-hover: #1d4ed8;
  --nav-active-bg: #e0e7ff;
  --nav-active-text: #1d4ed8;

  /* Typography & Layout */
  --font-family: system-ui, -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, Oxygen, Ubuntu, Cantarell, "Open Sans", "Helvetica Neue", sans-serif;
  --max-width: 800px;
  --radius: 8px;
  --transition-speed: 0.18s;
  --footer-height: 52px;
}

[data-theme="dark"] {
  /* Colors - Dark Theme */
  --bg-color: #0f172a;
  --surface-color: #1e293b;
  --surface-hover: #334155;
  --text-color: #f8fafc;
  --text-muted: #94a3b8;
  --border-color: #334155;
  --primary-color: #3b82f6;
  --primary-hover: #60a5fa;
  --nav-active-bg: #1e3a8a;
  --nav-active-text: #93c5fd;
}

html {
  box-sizing: border-box;
}

*, *::before, *::after {
  box-sizing: inherit;
}

body {
  font-family: var(--font-family);
  background-color: var(--bg-color);
  color: var(--text-color);
  transition: background-color var(--transition-speed) ease, color var(--transition-speed) ease;
  display: flex;
  flex-direction: column;
  min-height: 100vh;
  margin: 0;
}

/* Top bar with site title and theme switcher */
.top-bar {
  display: flex;
  justify-content: space-between;
  align-items: center;
  padding: 0.75rem 1.5rem;
  background-color: var(--surface-color);
  border-bottom: 1px solid var(--border-color);
}

.site-title {
  margin: 0;
  font-size: 1.25rem;
  font-weight: 700;
  letter-spacing: -0.02em;
  color: var(--text-color);
}

.theme-toggle {
  background: none;
  border: 1px solid var(--border-color);
  border-radius: var(--radius);
  color: var(--text-color);
  width: 36px;
  height: 36px;
  padding: 0;
  cursor: pointer;
  display: inline-flex;
  align-items: center;
  justify-content: center;
  transition: background-color var(--transition-speed), border-color var(--transition-speed), transform var(--transition-speed);
}

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

.theme-toggle:active {
  transform: scale(0.95);
}

.theme-toggle svg {
  width: 18px;
  height: 18px;
  stroke: currentColor;
  transition: transform var(--transition-speed) ease;
}

/* Navigation Bar */
.site-nav {
  background-color: var(--surface-color);
  border-bottom: 1px solid var(--border-color);
  padding: 0.35rem 1.5rem;
}

.site-nav__container {
  max-width: var(--max-width);
  margin: 0 auto;
  display: flex;
  align-items: center;
  justify-content: flex-start;
  position: relative;
}

.site-nav__hamburger {
  display: none;
  background: none;
  border: 1px solid var(--border-color);
  border-radius: var(--radius);
  color: var(--text-color);
  padding: 0.35rem 0.5rem;
  cursor: pointer;
  align-items: center;
  justify-content: center;
  margin-bottom: 0.25rem;
}

.site-nav__hamburger:hover {
  background-color: var(--surface-hover);
}

.site-nav__list {
  display: flex;
  list-style: none;
  margin: 0;
  padding: 0;
  gap: 0.5rem;
}

.site-nav__item {
  margin: 0;
}

.site-nav__link {
  display: inline-block;
  padding: 0.4rem 0.85rem;
  color: var(--text-muted);
  text-decoration: none;
  font-weight: 500;
  font-size: 0.9375rem;
  border-radius: var(--radius);
  transition: all var(--transition-speed) ease;
}

.site-nav__link:hover {
  color: var(--text-color);
  background-color: var(--surface-hover);
}

.site-nav__link.active {
  color: var(--nav-active-text);
  background-color: var(--nav-active-bg);
  font-weight: 600;
}

/* Main Container */
.container {
  width: 100%;
  max-width: var(--max-width);
  margin: 1.5rem auto;
  padding: 0 1.5rem calc(var(--footer-height) + 1.5rem); /* Extra bottom padding so content scrolls above fixed footer */
  flex: 1;
}

/* Fast, smooth view switching */
.page-view {
  display: none;
  opacity: 0;
  transform: translateY(6px);
  transition: opacity var(--transition-speed) ease, transform var(--transition-speed) ease;
}

.page-view.active {
  display: block;
}

.page-view.active.visible {
  opacity: 1;
  transform: translateY(0);
}

.card {
  background-color: var(--surface-color);
  border: 1px solid var(--border-color);
  border-radius: var(--radius);
  padding: 1.5rem;
  margin-bottom: 1.25rem;
  box-shadow: 0 1px 3px rgba(0, 0, 0, 0.04);
}

.card h2 {
  margin-top: 0;
  margin-bottom: 0.75rem;
  font-size: 1.5rem;
}

.card h3 {
  margin-top: 0;
  margin-bottom: 0.5rem;
  font-size: 1.2rem;
}

.card p {
  line-height: 1.6;
  margin: 0.6rem 0;
  color: var(--text-color);
}

/* Fixed Bottom Bar */
.bottom-bar {
  position: fixed;
  bottom: 0;
  left: 0;
  right: 0;
  height: var(--footer-height);
  display: flex;
  align-items: center;
  justify-content: center;
  background-color: var(--surface-color);
  border-top: 1px solid var(--border-color);
  font-size: 0.875rem;
  z-index: 100;
  box-shadow: 0 -2px 8px rgba(0, 0, 0, 0.04);
}

.bottom-bar__link {
  color: var(--text-muted);
}

.bottom-bar__link a {
  color: var(--primary-color);
  text-decoration: underline;
  text-underline-offset: 2px;
}

.bottom-bar__link a:hover {
  color: var(--primary-hover);
}

/* Link List Styling (e.g. See Also section) */
.link-list {
  display: flex;
  flex-direction: column;
  gap: 0.6rem;
  margin-top: 0.75rem;
}

.link-item {
  display: flex;
  align-items: baseline;
  line-height: 1.5;
  font-size: 0.95rem;
  color: var(--text-color);
}

.link-item__anchor {
  color: var(--primary-color);
  font-weight: 500;
  text-decoration: none;
  word-break: break-all;
  transition: color var(--transition-speed) ease, text-decoration var(--transition-speed) ease;
}

.link-item__anchor:hover {
  color: var(--primary-hover);
  text-decoration: underline;
  text-underline-offset: 2px;
}

.link-item__separator {
  margin: 0 0.5rem;
  color: var(--text-muted);
  user-select: none;
}

.link-item__title {
  color: var(--text-muted);
}

/* Quality check utilities */
.nowrap {
  white-space: nowrap;
}

.checkbox-item {
  display: flex;
  align-items: flex-start;
  gap: 0.5rem;
  margin-bottom: 0.5rem;
}

.checkbox-item input[type="checkbox"] {
  margin-top: 0.25rem; /* Ensures top-aligned with multiline text */
}

/* Responsive adjustments */
@media (max-width: 640px) {
  .site-nav__container.has-hamburger {
    flex-direction: column;
    align-items: flex-start;
  }

  .site-nav__container.has-hamburger .site-nav__hamburger {
    display: inline-flex;
  }

  .site-nav__container.has-hamburger .site-nav__list {
    display: none;
    flex-direction: column;
    width: 100%;
    gap: 0.25rem;
    padding-top: 0.5rem;
  }

  .site-nav__container.has-hamburger .site-nav__list.open {
    display: flex;
  }

  .site-nav__container.has-hamburger .site-nav__link {
    width: 100%;
    padding: 0.5rem 0.75rem;
  }
}