:root {
  color-scheme: dark;
  --bg: #070b15;
  --panel: rgba(13, 18, 34, 0.96);
  --panel-strong: #e2e8f0;
  --text: #d7dde7;
  --muted: #9aa4b8;
  --border: rgba(135, 149, 179, 0.14);
  --accent: #ffd54f;
  --accent-strong: #f9a825;
  --shadow: 0 20px 60px rgba(0, 0, 0, 0.35);
}

* {
  box-sizing: border-box;
}

html {
  scroll-behavior: smooth;
}

body {
  margin: 0;
  font-family: Inter, ui-sans-serif, system-ui, -apple-system, BlinkMacSystemFont, "Segoe UI", sans-serif;
  background: radial-gradient(circle at top left, rgba(42, 56, 91, 0.35), transparent 30%),
              radial-gradient(circle at bottom right, rgba(255, 213, 79, 0.12), transparent 25%),
              var(--bg);
  color: var(--text);
  min-height: 100vh;
  overflow-x: hidden;
}

button {
  font: inherit;
}

.page-header {
  position: sticky;
  top: 0;
  z-index: 50;
  backdrop-filter: blur(14px);
  background: rgba(4, 8, 18, 0.92);
  border-bottom: 1px solid rgba(255, 255, 255, 0.06);
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 1rem;
  padding: 1rem 1.25rem;
}

.page-title {
  font-size: 1rem;
  letter-spacing: 0.18em;
  text-transform: uppercase;
  font-weight: 700;
  color: var(--accent);
}

.top-directory {
  display: flex;
  flex-wrap: wrap;
  gap: 0.5rem;
  justify-content: flex-end;
}

.top-directory button {
  border: 1px solid rgba(255,255,255,0.14);
  background: rgba(255,255,255,0.04);
  color: var(--text);
  padding: 0.6rem 1rem;
  border-radius: 999px;
  cursor: pointer;
  transition: transform 0.2s ease, border-color 0.2s ease, background 0.2s ease;
}

.top-directory button:hover,
.top-directory button:focus {
  transform: translateY(-1px);
  border-color: rgba(255,213,79,0.55);
  background: rgba(255,255,255,0.08);
  outline: none;
}

.audio-controls {
  position: fixed;
  top: 96px;
  right: 0;
  width: 180px;
  padding: 0.75rem 0.75rem 1rem 0.75rem;
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: 0.5rem;
  z-index: 60;
  backdrop-filter: blur(18px);
  background: rgba(8, 13, 26, 0.94);
  border: 1px solid rgba(255, 255, 255, 0.08);
  border-radius: 24px 0 0 24px;
  transform: translateX(0);
  transition: transform 0.28s ease;
  overflow: visible;
}

.audio-controls.collapsed {
  transform: translateX(calc(100% - 44px));
}

.audio-controls.expanded {
  transform: translateX(0);
}

@media (min-width: 861px) {
  .audio-controls.collapsed {
    transform: translateX(0);
  }
}

.audio-controls audio {
  display: none;
}

.audio-tray-toggle {
  position: relative;
  align-self: flex-start;
  width: 40px;
  height: 40px;
  margin-left: -4px;
  border-radius: 50%;
  border: 1px solid rgba(255, 213, 79, 0.45);
  background: rgba(255, 213, 79, 0.18);
  color: var(--accent);
  display: grid;
  place-items: center;
  cursor: pointer;
  box-shadow: var(--shadow);
  transition: transform 0.2s ease, background 0.2s ease, border-color 0.2s ease;
}

.audio-tray-toggle:hover,
.audio-tray-toggle:focus {
  transform: translateY(-1px);
  border-color: rgba(255, 213, 79, 0.45);
  background: rgba(255, 255, 255, 0.1);
  outline: none;
}

.audio-status {
  color: var(--muted);
  font-size: 0.75rem;
  line-height: 1.4;
  text-align: center;
  max-width: 160px;
  padding: 0 0.25rem;
}

.audio-control-button {
  width: 44px;
  height: 44px;
  border-radius: 50%;
  border: 1px solid rgba(255, 255, 255, 0.12);
  background: rgba(8, 13, 26, 0.98);
  color: var(--text);
  display: grid;
  place-items: center;
  cursor: pointer;
  box-shadow: var(--shadow);
  transition: transform 0.2s ease, background 0.2s ease, border-color 0.2s ease;
}

.audio-control-button:hover,
.audio-control-button:focus {
  transform: translateY(-2px);
  border-color: rgba(255, 213, 79, 0.55);
  background: rgba(255, 255, 255, 0.08);
  outline: none;
}

.audio-control-button.active {
  background: linear-gradient(135deg, var(--accent), var(--accent-strong));
  color: #081018;
  border-color: rgba(255, 213, 79, 0.45);
}

.content {
  max-width: 1100px;
  margin: 0 auto;
  padding: 1.5rem 1.5rem 3rem;
}

.chapter {
  margin-bottom: 1.5rem;
  background: var(--panel);
  border: 1px solid var(--border);
  border-radius: 24px;
  overflow: hidden;
  box-shadow: var(--shadow);
  scroll-margin-top: 80px;
}

.chapter-header {
  display: grid;
  grid-template-columns: auto 1fr;
  gap: 1rem;
  align-items: center;
  padding: 1.25rem 1.5rem;
  cursor: pointer;
  background: linear-gradient(180deg, rgba(14,24,46,0.96), rgba(6,12,22,0.96));
}

.chapter-header:hover,
.chapter-header:focus-visible {
  background: linear-gradient(180deg, rgba(23,35,64,0.96), rgba(10,16,34,0.96));
}

.chapter-number {
  width: 3rem;
  height: 3rem;
  border-radius: 50%;
  display: grid;
  place-items: center;
  background: rgba(255, 213, 79, 0.14);
  color: var(--accent);
  font-weight: 700;
  border: 1px solid rgba(255,213,79,0.25);
}

.chapter-header h2 {
  font-size: 1.1rem;
  margin: 0;
  color: var(--text);
  line-height: 1.2;
}

.chapter-subtitle {
  margin: 0.6rem 0 0;
  color: var(--muted);
  font-size: 0.92rem;
}

.chapter-body {
  display: none;
  padding: 1.5rem;
  color: var(--text);
  line-height: 1.75;
}

.chapter.expanded .chapter-body {
  display: block;
}

.chapter-body h3 {
  color: var(--accent);
  margin-top: 1.5rem;
  margin-bottom: 1rem;
}

.chapter-body p {
  margin: 0 0 1rem;
}

.chapter-art {
  width: 100%;
  max-width: 32%;
  height: auto;
  display: block;
  margin: 0 auto 1.25rem;
  border-radius: 20px;
  border: 1px solid rgba(255,255,255,0.08);
}

.collapse-footer {
  display: flex;
  justify-content: flex-end;
  padding-top: 1rem;
}

.collapse-button {
  border: 1px solid rgba(255,255,255,0.18);
  background: transparent;
  color: var(--accent);
  padding: 0.85rem 1.2rem;
  border-radius: 999px;
  cursor: pointer;
  transition: background 0.2s ease, transform 0.2s ease;
}

.collapse-button:hover,
.collapse-button:focus {
  background: rgba(255,213,79,0.12);
  transform: translateY(-1px);
  outline: none;
}

@media (max-width: 1024px) {
  .audio-controls {
    top: 84px;
    right: 12px;
  }

  .chapter-art {
    max-width: 40%;
  }
}

@media (max-width: 860px) {
  .page-header {
    flex-direction: column;
    align-items: stretch;
  }

  .top-directory {
    justify-content: center;
  }

  .chapter-header {
    grid-template-columns: 1fr;
  }

  .chapter-number {
    justify-self: start;
  }
}

@media (max-width: 720px) {
  .audio-controls {
    top: 72px;
    right: 8px;
  }

  .audio-control-button {
    width: 46px;
    height: 46px;
  }

  .chapter-art {
    max-width: 90%;
  }

  .chapter-header {
    padding: 1rem;
  }

  .chapter-body {
    padding: 1rem;
  }
}

@media (max-width: 540px) {
  .top-directory button {
    padding: 0.55rem 0.8rem;
    font-size: 0.88rem;
  }
}