:root {
  --session-bg: var(--color-bg, #f6f5f1);
  --session-surface: var(--color-surface, #f9f8f5);
  --session-border: var(--color-divider, #dddbd7);
  --session-text: var(--color-text, #1a1917);
  --session-muted: var(--color-text-muted, #6b6965);
  --session-primary: var(--color-primary, #14365a);
  --session-accent: var(--color-accent, #c5813d);
  --session-font: var(--font-body, 'DM Sans', 'Helvetica Neue', Arial, sans-serif);
  --session-display: var(--font-display, 'Instrument Serif', Georgia, serif);
}

[data-theme="dark"] {
  --session-bg: var(--color-bg, #131210);
  --session-surface: var(--color-surface, #1a1916);
  --session-border: var(--color-divider, #2e2c29);
  --session-text: var(--color-text, #d4d2ce);
  --session-muted: var(--color-text-muted, #888580);
  --session-primary: var(--color-primary, #7aafd4);
  --session-accent: var(--color-accent, #e09e5a);
}

html {
  scroll-padding-top: 116px;
}

.sr-only:focus,
.sr-only:focus-visible {
  position: fixed;
  top: 12px;
  left: 12px;
  z-index: 300;
  width: auto;
  height: auto;
  margin: 0;
  padding: 0.75rem 1rem;
  overflow: visible;
  clip: auto;
  white-space: normal;
  background: var(--session-text);
  color: var(--session-bg);
  border-radius: 6px;
  font-family: var(--session-font);
  font-size: 0.875rem;
  font-weight: 600;
  text-decoration: none;
  box-shadow: 0 8px 24px rgb(0 0 0 / 0.18);
}

.session-nav {
  position: fixed;
  top: 0;
  left: 0;
  right: 0;
  z-index: 100;
  background: color-mix(in srgb, var(--session-bg) 92%, transparent);
  backdrop-filter: blur(16px);
  border-bottom: 1px solid var(--session-border);
}

.session-nav__inner {
  max-width: 1100px;
  margin-inline: auto;
  padding-inline: clamp(1rem, 5vw, 3rem);
  height: 60px;
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 1rem;
}

.session-nav__logo {
  display: flex;
  align-items: center;
  gap: 0.75rem;
  color: var(--session-text);
  text-decoration: none;
  min-width: 0;
}

.session-nav__mark {
  width: 34px;
  height: 34px;
  flex-shrink: 0;
}

.session-nav__name {
  font-family: var(--session-display);
  font-size: 0.95rem;
  color: var(--session-text);
  white-space: nowrap;
}

.session-nav__right {
  display: flex;
  align-items: center;
  gap: 0.625rem;
  flex-shrink: 0;
}

.session-nav__theme {
  width: 36px;
  height: 36px;
  display: flex;
  align-items: center;
  justify-content: center;
  color: var(--session-muted);
  border-radius: 8px;
  background: none;
  border: none;
  cursor: pointer;
}

.session-nav__theme:hover {
  color: var(--session-text);
  background: color-mix(in srgb, var(--session-text) 7%, transparent);
}

.session-nav__back {
  font-family: var(--session-font);
  font-size: 0.75rem;
  font-weight: 600;
  display: flex;
  align-items: center;
  gap: 0.5rem;
  color: var(--session-muted);
  padding: 0.5rem 0.875rem;
  border: 1px solid var(--session-border);
  border-radius: 9999px;
  text-decoration: none;
}

.session-nav__back:hover {
  color: var(--session-primary);
  border-color: var(--session-primary);
}

.session-progress {
  position: fixed;
  top: 60px;
  left: 0;
  right: 0;
  z-index: 90;
  background: var(--session-surface);
  border-bottom: 1px solid var(--session-border);
  padding: 0.75rem clamp(1rem, 5vw, 3rem);
}

.session-progress__inner {
  max-width: 1100px;
  margin-inline: auto;
  display: flex;
  align-items: center;
  gap: 0.75rem;
}

.session-progress__label {
  font-family: var(--session-font);
  font-size: 0.75rem;
  font-weight: 600;
  color: var(--session-muted);
  white-space: nowrap;
}

.session-progress__track {
  flex: 1;
  height: 6px;
  background: var(--session-border);
  border-radius: 3px;
  overflow: hidden;
}

.session-progress__fill {
  width: 0%;
  height: 100%;
  background: linear-gradient(90deg, var(--session-primary), var(--session-accent));
  border-radius: 3px;
  transition: width 0.2s;
}

.session-shell-offset {
  margin-top: 96px;
}

.session-footer {
  border-top: 1px solid var(--session-border);
  background: var(--session-surface);
  padding: 2rem clamp(1rem, 5vw, 3rem);
}

.session-footer__inner {
  max-width: 1100px;
  margin-inline: auto;
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 1rem;
  flex-wrap: wrap;
}

.session-footer__copy {
  font-family: var(--session-font);
  font-size: 0.75rem;
  color: var(--session-muted);
  margin: 0;
}

.session-footer__links {
  list-style: none;
  display: flex;
  gap: 1rem;
  margin: 0;
  padding: 0;
}

.session-footer__links a {
  font-family: var(--session-font);
  font-size: 0.75rem;
  color: var(--session-muted);
  text-decoration: none;
}

.session-footer__links a:hover {
  color: var(--session-primary);
}

.scroll-top {
  position: fixed;
  right: 1.5rem;
  bottom: 1.5rem;
  width: 44px;
  height: 44px;
  display: flex;
  align-items: center;
  justify-content: center;
  background: var(--session-primary);
  color: #fff;
  border: none;
  border-radius: 9999px;
  opacity: 0;
  pointer-events: none;
  cursor: pointer;
  transition: opacity 0.2s;
  z-index: 80;
}

.scroll-top.visible {
  opacity: 1;
  pointer-events: auto;
}

@media (max-width: 640px) {
  .session-nav__name {
    display: none;
  }

  .session-nav__back {
    padding-inline: 0.75rem;
  }

  .session-footer__inner {
    flex-direction: column;
    align-items: flex-start;
  }
}