/* ============================================================================
   Pulse Music — Common Layout & Components
   Loads after tokens.css. Provides header, footer, containers, utility classes.
   ============================================================================ */

/* ========== HEADER ========== */

.site-header {
  position: sticky;
  top: 0;
  z-index: 20;
  background: rgba(10, 10, 15, 0.88);
  backdrop-filter: blur(8px);
  -webkit-backdrop-filter: blur(8px);
  border-bottom: 1px solid var(--gold-line);
  height: 56px;
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding: 0 var(--page-padding-x);
}

.site-header__brand {
  display: flex;
  align-items: center;
  gap: 10px;
  text-decoration: none;
  color: var(--text-primary);
  font: 500 var(--size-small)/1 var(--font-label);
  letter-spacing: 0.08em;
}
.site-header__brand:hover { color: var(--gold); }

.site-header__pulse {
  width: 7px;
  height: 7px;
  border-radius: 50%;
  background: var(--gold);
  box-shadow: 0 0 8px var(--gold-soft);
  animation: site-pulse var(--beat-ms, 500ms) var(--ease-kick) infinite;
}
@keyframes site-pulse {
  0%, 100% { transform: scale(1); opacity: 0.85; }
  12%      { transform: scale(1.35); opacity: 1; }
  50%      { transform: scale(1); opacity: 0.85; }
}
@media (prefers-reduced-motion: reduce) {
  .site-header__pulse { animation: none; }
}

.site-header__nav {
  display: flex;
  gap: 24px;
  align-items: center;
}
.site-header__nav a {
  color: var(--text-body);
  text-decoration: none;
  font: 400 var(--size-label)/1 var(--font-label);
  letter-spacing: 0.1em;
  text-transform: uppercase;
  transition: color var(--quarter-beat-ms) var(--ease-kick);
}
.site-header__nav a:hover { color: var(--gold); }
.site-header__nav a[aria-current="page"] { color: var(--gold); }

.site-header__parent {
  color: var(--text-muted);
  font-size: 0.88em;
}
.site-header__parent::before {
  content: "↖";
  margin-right: 4px;
  opacity: 0.7;
}

@media (max-width: 640px) {
  .site-header__nav a:not(.site-header__parent) { display: none; }
  .site-header__parent { font-size: 0.92em; }
}

/* ========== CONTAINERS ========== */

.container {
  max-width: var(--content-max);
  margin: 0 auto;
  padding: 0 var(--page-padding-x);
}
.container--wide {
  max-width: var(--content-wide);
}

/* ========== SECTIONS ========== */

.section {
  padding: var(--section-gap) 0;
}
.section--first {
  padding-top: clamp(32px, 5vh, 64px);
}

/* ========== TYPOGRAPHY ========== */

.eyebrow {
  font: 500 var(--size-label)/1.3 var(--font-label);
  letter-spacing: 0.22em;
  text-transform: uppercase;
  color: var(--gold-dim);
  margin: 0 0 16px;
}

.heading-hero {
  font: 300 var(--size-hero)/1.05 var(--font-display);
  color: var(--text-primary);
  margin: 0 0 24px;
  letter-spacing: -0.01em;
}

.heading-1 {
  font: 400 var(--size-h1)/1.15 var(--font-display);
  color: var(--text-primary);
  margin: 0 0 20px;
  letter-spacing: -0.005em;
}

.heading-2 {
  font: 400 var(--size-h2)/1.2 var(--font-display);
  color: var(--text-primary);
  margin: 2em 0 0.6em;
}

.heading-3 {
  font: 500 var(--size-h3)/1.3 var(--font-display);
  color: var(--text-primary);
  margin: 1.8em 0 0.5em;
}

.lead {
  font: 400 var(--size-lead)/1.65 var(--font-body);
  color: var(--text-body);
  font-style: italic;
  margin: 0 0 2em;
  max-width: 640px;
}

.prose p {
  font: 400 var(--size-body)/1.75 var(--font-body);
  color: var(--text-body);
  margin: 0 0 1.3em;
}
.prose p:last-child { margin-bottom: 0; }

.prose em {
  color: var(--text-primary);
  font-style: italic;
}
.prose strong {
  color: var(--text-primary);
  font-weight: 600;
}
.prose a {
  color: var(--gold);
  text-decoration: underline;
  text-decoration-color: var(--gold-line);
  text-underline-offset: 3px;
  transition: text-decoration-color var(--quarter-beat-ms) var(--ease-kick);
}
.prose a:hover,
.prose a:focus-visible {
  text-decoration-color: var(--gold);
}

.prose ul, .prose ol {
  padding-left: 1.5em;
  margin: 0 0 1.3em;
  color: var(--text-body);
  font: 400 var(--size-body)/1.75 var(--font-body);
}
.prose li { margin-bottom: 0.5em; }

.prose blockquote {
  margin: 1.8em 0;
  padding: 16px 22px;
  background: var(--void-raised);
  border-left: 3px solid var(--gold);
  border-radius: 0 4px 4px 0;
  font: 400 var(--size-body)/1.7 var(--font-body);
  color: var(--text-body);
}
.prose blockquote p { margin: 0; }
.prose blockquote p + p { margin-top: 0.8em; }

.prose code {
  font-family: "SFMono-Regular", "Menlo", monospace;
  font-size: 0.9em;
  background: var(--void-raised);
  padding: 1px 6px;
  border-radius: 3px;
  color: var(--text-primary);
}

/* Framework term — distinctive treatment, links to glossary */
.term {
  font-family: var(--font-label);
  font-weight: 500;
  font-size: var(--term-size);
  letter-spacing: var(--term-tracking);
  color: var(--term-color);
  text-decoration: none;
  border-bottom: 1px dotted var(--gold-line);
  transition: color var(--quarter-beat-ms) var(--ease-kick),
              border-color var(--quarter-beat-ms) var(--ease-kick);
}
.term:hover,
.term:focus-visible {
  color: var(--gold);
  border-color: var(--gold);
}

/* ========== CARDS ========== */

.card {
  background: var(--void-raised);
  border: 1px solid var(--gold-line);
  border-radius: 6px;
  padding: 24px;
  text-decoration: none;
  color: var(--text-body);
  transition: border-color var(--quarter-beat-ms) var(--ease-kick),
              background var(--quarter-beat-ms) var(--ease-kick),
              transform var(--quarter-beat-ms) var(--ease-kick);
  display: flex;
  flex-direction: column;
  gap: 12px;
}
.card:hover,
.card:focus-visible {
  border-color: var(--gold);
  background: var(--void-overlay);
  transform: translateY(-1px);
}
.card__eyebrow {
  font: 500 var(--size-label)/1.3 var(--font-label);
  letter-spacing: 0.2em;
  text-transform: uppercase;
  color: var(--gold-dim);
}
.card__title {
  font: 500 var(--size-h3)/1.25 var(--font-display);
  color: var(--text-primary);
  margin: 0;
}
.card__desc {
  font: 400 var(--size-small)/1.6 var(--font-body);
  color: var(--text-body);
  margin: 0;
}
.card__arrow {
  margin-top: auto;
  color: var(--gold);
  font: 500 var(--size-label)/1 var(--font-label);
  letter-spacing: 0.14em;
  text-transform: uppercase;
}

/* ========== CHAPTER LAYOUT ========== */

.chapter {
  display: grid;
  grid-template-columns: 220px minmax(0, var(--content-max));
  gap: 48px;
  max-width: var(--content-wide);
  margin: 0 auto;
  padding: var(--section-gap) var(--page-padding-x);
}

.chapter__sidebar {
  position: sticky;
  top: 80px;
  align-self: start;
  height: max-content;
}
.chapter__sidebar-label {
  font: 500 var(--size-label)/1.3 var(--font-label);
  letter-spacing: 0.18em;
  text-transform: uppercase;
  color: var(--gold-dim);
  margin: 0 0 16px;
}
.chapter__sidebar-list {
  list-style: none;
  padding: 0;
  margin: 0 0 32px;
}
.chapter__sidebar-list li {
  margin-bottom: 8px;
  position: relative;
}
.chapter__sidebar-list a {
  display: block;
  padding: 4px 0 4px 14px;
  color: var(--text-muted);
  text-decoration: none;
  font: 400 var(--size-small)/1.4 var(--font-body);
  border-left: 2px solid transparent;
  transition: color var(--quarter-beat-ms) var(--ease-kick),
              border-color var(--quarter-beat-ms) var(--ease-kick);
}
.chapter__sidebar-list a:hover,
.chapter__sidebar-list a:focus-visible {
  color: var(--text-primary);
  border-color: var(--gold-line);
}
.chapter__sidebar-list a[data-active="true"] {
  color: var(--gold);
  border-color: var(--gold);
}

.chapter__related {
  margin-top: 24px;
  padding-top: 20px;
  border-top: 1px solid var(--gold-line);
  font: 400 var(--size-small)/1.5 var(--font-body);
  color: var(--text-muted);
}
.chapter__related a {
  color: var(--text-body);
  text-decoration: none;
  display: block;
  margin-bottom: 4px;
}
.chapter__related a:hover { color: var(--gold); }

.chapter__body {
  max-width: var(--content-max);
}

.chapter__header {
  margin-bottom: 48px;
  padding-bottom: 24px;
  border-bottom: 1px solid var(--gold-line);
}
.chapter__number {
  font: 500 var(--size-label)/1.3 var(--font-label);
  letter-spacing: 0.24em;
  text-transform: uppercase;
  color: var(--gold);
  margin: 0 0 12px;
}
.chapter__title {
  font: 300 var(--size-h1)/1.1 var(--font-display);
  color: var(--text-primary);
  margin: 0 0 8px;
}
.chapter__subtitle {
  font: 400 var(--size-lead)/1.5 var(--font-display);
  color: var(--text-body);
  font-style: italic;
  margin: 0;
}
.chapter__meta {
  margin-top: 24px;
  font: 400 var(--size-small)/1.5 var(--font-label);
  letter-spacing: 0.12em;
  text-transform: uppercase;
  color: var(--text-muted);
}

.chapter__section {
  margin-bottom: 56px;
  scroll-margin-top: 80px;
}
.chapter__section-number {
  font: 500 var(--size-label)/1.3 var(--font-label);
  letter-spacing: 0.22em;
  text-transform: uppercase;
  color: var(--gold-dim);
  margin: 0 0 8px;
}
.chapter__section-title {
  font: 400 var(--size-h2)/1.15 var(--font-display);
  color: var(--text-primary);
  margin: 0 0 24px;
  letter-spacing: -0.005em;
}

/* "See also" cross-reference card at the end of a section */
.see-also {
  display: block;
  margin-top: 28px;
  padding: 14px 18px;
  background: var(--void-raised);
  border: 1px solid var(--gold-line);
  border-radius: 4px;
  text-decoration: none;
  color: var(--text-body);
  font: 400 var(--size-small)/1.5 var(--font-body);
  transition: border-color var(--quarter-beat-ms) var(--ease-kick),
              background var(--quarter-beat-ms) var(--ease-kick);
}
.see-also:hover,
.see-also:focus-visible {
  background: var(--void-overlay);
  border-color: var(--gold);
}
.see-also__label {
  display: block;
  font-family: var(--font-label);
  font-weight: 600;
  font-size: 0.8em;
  letter-spacing: 0.14em;
  text-transform: uppercase;
  color: var(--gold-dim);
  margin-bottom: 4px;
}
.see-also__title {
  color: var(--text-primary);
}
.see-also::after {
  content: " →";
  color: var(--gold);
}

/* Mobile: sidebar collapses to top dropdown */
@media (max-width: 900px) {
  .chapter {
    grid-template-columns: 1fr;
    gap: 32px;
  }
  .chapter__sidebar {
    position: relative;
    top: 0;
  }
  .chapter__sidebar-list {
    display: grid;
    grid-template-columns: repeat(auto-fill, minmax(160px, 1fr));
    gap: 4px;
    margin: 0 0 16px;
  }
  .chapter__sidebar-list li { margin: 0; }
}

/* ========== AUDIO EXAMPLE (shared with prototype) ========== */

.audio-example {
  background: var(--surface-audio);
  border: 1px solid var(--surface-audio-edge);
  border-radius: var(--audio-block-radius);
  padding: var(--audio-block-padding);
  display: flex;
  flex-direction: column;
  gap: 12px;
  margin: 2em 0;
}
.audio-example__label {
  font: 600 var(--size-label)/1.3 var(--font-label);
  letter-spacing: 0.14em;
  text-transform: uppercase;
  color: var(--gold-dim);
  margin: 0;
}
.audio-example__title {
  font: 500 var(--size-lead)/1.3 var(--font-display);
  color: var(--text-primary);
  margin: 0;
}
.audio-example__caption {
  font: 400 var(--size-small)/1.6 var(--font-body);
  color: var(--text-body);
  margin: 0;
}
.audio-example__player { margin-top: 4px; }
.audio-example__player audio {
  width: 100%;
  height: 40px;
  filter: invert(0.92) hue-rotate(180deg) saturate(0.8);
  border-radius: 4px;
  accent-color: var(--gold);
}
.audio-example__player audio:focus-visible {
  outline: 2px solid var(--gold);
  outline-offset: 2px;
}
.audio-example__listen-for {
  margin: 0;
  padding: 10px 14px;
  background: var(--void-raised);
  border-left: 2px solid var(--gold-line);
  font: 400 var(--size-small)/1.55 var(--font-body);
  color: var(--text-body);
}
.audio-example__listen-for strong {
  font-family: var(--font-label);
  font-weight: 600;
  font-size: 0.88em;
  letter-spacing: 0.1em;
  text-transform: uppercase;
  color: var(--gold-dim);
  display: block;
  margin-bottom: 4px;
}
.audio-example--pending .audio-example__player {
  display: flex;
  align-items: center;
  justify-content: center;
  min-height: 60px;
  padding: 16px 20px;
  background: var(--void-raised);
  border: 1px dashed var(--gold-line);
  border-radius: 4px;
  font: 400 var(--size-small)/1.4 var(--font-label);
  color: var(--text-muted);
  text-align: center;
}
.audio-example--pending .audio-example__player::before {
  content: "Audio example in production";
}

/* ========== FOOTER ========== */

.site-footer {
  border-top: 1px solid var(--gold-line);
  padding: 40px var(--page-padding-x);
  margin-top: var(--section-gap);
  text-align: center;
  color: var(--text-muted);
  font: 400 var(--size-small)/1.6 var(--font-body);
}
.site-footer a {
  color: var(--text-body);
  text-decoration: none;
  transition: color var(--quarter-beat-ms) var(--ease-kick);
}
.site-footer a:hover { color: var(--gold); }
.site-footer__closing {
  font-style: italic;
  color: var(--text-body);
  margin: 0 0 12px;
}

/* ========== SCROLL REVEAL ========== */

.reveal {
  opacity: 0;
  transform: translateY(24px);
  transition: opacity var(--dur-reveal) var(--ease-reveal),
              transform var(--dur-reveal) var(--ease-reveal);
}
.reveal[data-revealed="true"] {
  opacity: 1;
  transform: translateY(0);
}
@media (prefers-reduced-motion: reduce) {
  .reveal {
    opacity: 1;
    transform: none;
    transition: none;
  }
}