/* ==========================================================================
   layout.css — topbar, progress rail, hero, chapter grid, keyboard dock
   ========================================================================== */

/* --------------------------------------------------------------------------
   Top bar
   -------------------------------------------------------------------------- */
.topbar {
  position: fixed;
  top: 0;
  left: 0;
  right: 0;
  z-index: 100;
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 1rem;
  padding: 0.9rem clamp(1.2rem, 4vw, 3rem);
  background: linear-gradient(to bottom, color-mix(in srgb, var(--bg) 82%, transparent), transparent);
  pointer-events: none;
}

.topbar > * { pointer-events: auto; }

.topbar-brand {
  font-family: var(--font-display);
  font-weight: 600;
  font-size: 0.95rem;
  letter-spacing: 0.3em;
  border-bottom: none;
  color: var(--ink);
}

.topbar-era {
  font-family: var(--font-mono);
  font-size: 0.68rem;
  letter-spacing: 0.22em;
  color: var(--ink-dim);
  transition: opacity 0.6s ease;
}

.topbar-actions {
  display: inline-flex;
  align-items: center;
  gap: 0.55rem;
}

.topbar-lang {
  display: inline-grid;
  place-items: center;
  min-width: 2.5rem;
  min-height: 2.1rem;
  padding: 0.35rem 0.65rem;
  color: var(--ink-dim);
  border: 1px solid var(--line);
  border-radius: 999px;
  font-size: 0.66rem;
  letter-spacing: 0.16em;
  text-decoration: none;
  transition: color 0.3s ease, border-color 0.3s ease, background-color 0.3s ease;
}

.topbar-lang:hover,
.topbar-lang:focus-visible {
  color: var(--accent);
  border-color: var(--accent);
  background: color-mix(in srgb, var(--accent) 8%, transparent);
}

.topbar-sound {
  display: inline-flex;
  align-items: center;
  gap: 0.5rem;
  font-family: var(--font-mono);
  font-size: 0.68rem;
  letter-spacing: 0.18em;
  color: var(--ink-dim);
  padding: 0.4rem 0.9rem;
  border: 1px solid var(--line);
  border-radius: 999px;
  transition: color 0.3s ease, border-color 0.3s ease;
}

.topbar-sound:hover { color: var(--accent); border-color: var(--accent); }
.topbar-sound[aria-pressed='true'] { color: var(--accent); border-color: var(--accent); }
.topbar-sound[aria-pressed='false'] .icon-wave { opacity: 0.2; }

html[lang='en'] .topbar-brand {
  letter-spacing: 0.12em;
}

html[lang='en'] .hero-title {
  max-width: 12ch;
  font-size: clamp(3.45rem, 8.4vw, 8.8rem);
  line-height: 0.92;
}

html[lang='en'] .chapter-title {
  text-wrap: balance;
}

/* --------------------------------------------------------------------------
   Progress rail — a punched paper strip beside the page
   -------------------------------------------------------------------------- */
.rail {
  position: fixed;
  right: clamp(0.6rem, 2vw, 1.8rem);
  top: 50%;
  transform: translateY(-54%);
  z-index: 90;
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: 0.55rem;
  padding: 1rem 0.5rem;
  border-radius: 999px;
  background: color-mix(in srgb, var(--bg-soft) 72%, transparent);
  border: 1px solid var(--line);
  backdrop-filter: blur(6px);
}

.rail-hole {
  position: relative;
  width: 9px;
  height: 9px;
  border-radius: 50%;
  border: 1px solid var(--ink-dim);
  background: transparent;
  padding: 0;
  transition: background-color 0.4s ease, border-color 0.4s ease, transform 0.4s ease;
}

.rail-hole:hover { transform: scale(1.5); border-color: var(--accent); }

.rail-hole.is-past { background: var(--ink-dim); border-color: var(--ink-dim); }

.rail-hole.is-active {
  background: var(--accent);
  border-color: var(--accent);
  transform: scale(1.45);
  box-shadow: 0 0 12px var(--accent-soft), 0 0 4px var(--accent);
}

.rail-hole .rail-tip {
  position: absolute;
  right: 20px;
  top: 50%;
  transform: translateY(-50%) translateX(6px);
  font-family: var(--font-mono);
  font-size: 0.62rem;
  letter-spacing: 0.14em;
  white-space: nowrap;
  color: var(--ink);
  background: color-mix(in srgb, var(--bg-soft) 92%, transparent);
  border: 1px solid var(--line);
  padding: 0.2rem 0.55rem;
  border-radius: 4px;
  opacity: 0;
  pointer-events: none;
  transition: opacity 0.25s ease, transform 0.25s ease;
}

.rail-hole:hover .rail-tip,
.rail-hole:focus-visible .rail-tip {
  opacity: 1;
  transform: translateY(-50%) translateX(0);
}

@media (max-width: 720px) {
  .rail { display: none; }
}

@media (max-width: 560px) {
  .topbar {
    gap: 0.55rem;
  }

  .topbar-brand {
    max-width: 48vw;
    overflow: hidden;
    text-overflow: ellipsis;
    white-space: nowrap;
  }

  .topbar-actions {
    gap: 0.35rem;
  }

  .topbar-lang {
    min-width: 2.2rem;
    padding-inline: 0.5rem;
  }

  .topbar-sound {
    padding-inline: 0.65rem;
  }
}

/* --------------------------------------------------------------------------
   Hero
   -------------------------------------------------------------------------- */
.hero {
  position: relative;
  min-height: 100svh;
  display: grid;
  place-items: center;
  overflow: hidden;
  padding: 4rem 1.5rem calc(var(--dock-height) + 2rem);
}

.chapter {
  scroll-margin-top: 4.75rem;
}

.hero-canvas {
  position: absolute;
  inset: 0;
  width: 100%;
  height: 100%;
  opacity: 0.6;
}

.hero-inner {
  position: relative;
  z-index: 2;
  text-align: center;
  max-width: 60rem;
}

.hero-eyebrow {
  color: var(--ink-dim);
  margin-bottom: 2.2rem;
}

.hero-title {
  font-weight: 900;
  line-height: 1.12;
  margin: 0 0 2.2rem;
}

.hero-title-line {
  display: block;
  font-size: clamp(2.2rem, 6.5vw, 4.6rem);
  letter-spacing: 0.12em;
}

.hero-title-em {
  font-size: clamp(3.2rem, 10.5vw, 7.6rem);
  color: var(--accent);
  letter-spacing: 0.06em;
  text-shadow: 0 0 80px var(--accent-soft);
}

.hero-sub {
  color: var(--ink-dim);
  font-size: clamp(0.92rem, 1.4vw, 1.05rem);
  line-height: 2.2;
  margin-bottom: 3rem;
}

.hero-actions {
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: 1.3rem;
}

.hero-hint { color: var(--ink-dim); opacity: 0.8; }

.hero-scroll-cue {
  margin-top: 3rem;
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: 0.6rem;
  color: var(--ink-dim);
}

.hero-scroll-cue i {
  width: 1px;
  height: 44px;
  background: linear-gradient(to bottom, var(--accent), transparent);
  animation: cue-drop 2.2s ease-in-out infinite;
}

@keyframes cue-drop {
  0% { transform: scaleY(0); transform-origin: top; }
  55% { transform: scaleY(1); transform-origin: top; }
  56% { transform-origin: bottom; }
  100% { transform: scaleY(0); transform-origin: bottom; }
}

/* --------------------------------------------------------------------------
   Chapters
   -------------------------------------------------------------------------- */
.chapter {
  position: relative;
  padding: clamp(6rem, 14vh, 10rem) clamp(1.2rem, 5vw, 4rem) clamp(5rem, 10vh, 8rem);
}

.chapter-inner {
  max-width: 72rem;
  margin: 0 auto;
}

.chapter-head { margin-bottom: clamp(2.4rem, 5vh, 4rem); max-width: 46rem; }

.chapter-head-center {
  margin-inline: auto;
  text-align: center;
  max-width: 52rem;
}

.chapter-eyebrow {
  color: var(--accent);
  margin: 0 0 0.4rem;
}

.chapter-yearline {
  display: flex;
  align-items: baseline;
  gap: 0.9rem;
}

.chapter-head-center .chapter-yearline { justify-content: center; }

.chapter-year {
  font-family: var(--font-display);
  font-optical-sizing: auto;
  font-weight: 900;
  font-size: clamp(4.4rem, 11vw, 8.5rem);
  line-height: 1;
  color: transparent;
  -webkit-text-stroke: 1.5px var(--accent);
  letter-spacing: 0.02em;
  transition: -webkit-text-stroke-color 1.4s ease;
}

.chapter-yearnote { color: var(--ink-dim); }

.chapter-title {
  font-size: clamp(1.5rem, 3.2vw, 2.3rem);
  font-weight: 600;
  letter-spacing: 0.06em;
  line-height: 1.5;
  margin-top: 1.1rem;
}

.chapter-lede {
  color: var(--ink-dim);
  margin-top: 1.2rem;
  font-size: 0.98rem;
}

.chapter-body {
  display: grid;
  grid-template-columns: minmax(0, 7fr) minmax(0, 5fr);
  gap: clamp(2rem, 5vw, 5rem);
  align-items: start;
  margin-bottom: clamp(2.4rem, 5vh, 3.6rem);
}

.chapter-flip .chapter-body { grid-template-columns: minmax(0, 5fr) minmax(0, 7fr); }
.chapter-flip .chapter-text { order: 2; }
.chapter-flip .chapter-figure { order: 1; }

.chapter-body-narrow { margin-top: clamp(2.4rem, 5vh, 3.6rem); }

.chapter-text { max-width: 40rem; }
.chapter-text p + p { margin-top: 1.2em; }

/* Figures */
.chapter-figure {
  margin: 0;
  position: relative;
}

.chapter-figure img {
  width: 100%;
  border-radius: 4px;
  filter: sepia(0.24) contrast(0.96) brightness(0.92);
  box-shadow: 0 30px 70px -30px rgba(0, 0, 0, 0.8), 0 0 0 1px var(--line);
  transition: filter 0.6s ease, transform 0.6s ease;
}

.chapter-figure:hover img { filter: sepia(0.05) contrast(1) brightness(1); }

.chapter-figure figcaption {
  margin-top: 0.9rem;
  font-size: 0.78rem;
  line-height: 1.8;
  color: var(--ink-dim);
}

.chapter-figure figcaption .mono { display: block; opacity: 0.75; margin-top: 0.15rem; }

.chapter-figure-svg svg {
  width: 100%;
  height: auto;
  color: var(--accent);
  background: var(--accent-soft);
  border: 1px solid var(--line);
  border-radius: 4px;
  padding: clamp(1rem, 3vw, 2rem);
}

/* Broken remote image: hide it, keep the caption as a label card */
.chapter-figure.img-failed img { display: none; }

.chapter-figure.img-failed::before {
  content: '图片暂不可用';
  display: grid;
  place-items: center;
  aspect-ratio: 4 / 3;
  border: 1px dashed var(--line);
  border-radius: 4px;
  color: var(--ink-dim);
  font-size: 0.85rem;
}

/* Module chapters (anatomy / compass / roll) */
.chapter-module .chapter-head { margin-bottom: clamp(2rem, 4vh, 3rem); }

/* Coda */
.chapter-coda {
  min-height: 90svh;
  display: grid;
  align-items: center;
  padding-bottom: calc(var(--dock-height) + 4rem);
  text-align: center;
}

.coda-text {
  max-width: 42rem;
  margin: 0 auto clamp(2rem, 4vh, 3rem);
  font-size: clamp(1.05rem, 1.8vw, 1.25rem);
  line-height: 2.3;
}

/* --------------------------------------------------------------------------
   Keyboard dock
   -------------------------------------------------------------------------- */
.dock {
  position: fixed;
  left: 0;
  right: 0;
  bottom: 0;
  z-index: 110;
  background: color-mix(in srgb, var(--ebony) 88%, var(--bg));
  border-top: 1px solid var(--line);
  box-shadow: 0 -24px 60px -18px rgba(0, 0, 0, 0.75);
  backdrop-filter: blur(10px);
  transition: transform 0.5s cubic-bezier(0.3, 0.9, 0.3, 1);
}

.dock[data-collapsed='true'] { transform: translateY(calc(100% - 2.4rem)); }

.dock-head {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 1rem;
  padding: 0.45rem clamp(1rem, 3vw, 2.2rem);
}

.dock-info {
  display: flex;
  align-items: baseline;
  gap: 1.2rem;
  min-width: 0;
}

.dock-era {
  color: var(--accent);
  font-size: 0.72rem;
  letter-spacing: 0.2em;
  white-space: nowrap;
  overflow: hidden;
  text-overflow: ellipsis;
  transition: color 1.4s ease;
}

.dock-range { color: var(--ink-dim); font-size: 0.62rem; white-space: nowrap; }

.dock-toggle {
  color: var(--ink-dim);
  font-size: 0.62rem;
  letter-spacing: 0.2em;
  padding: 0.25rem 0.7rem;
  border: 1px solid var(--line);
  border-radius: 999px;
  white-space: nowrap;
  flex-shrink: 0;
  transition: color 0.3s ease, border-color 0.3s ease;
}

.dock-toggle:hover { color: var(--accent); border-color: var(--accent); }

.dock-keys {
  position: relative;
  height: 118px;
  margin: 0 clamp(0.6rem, 2vw, 1.6rem) 0.7rem;
  overflow-x: auto;
  overflow-y: hidden;
  scrollbar-width: none;
}

.dock-keys::-webkit-scrollbar { display: none; }

.dock-keys-inner {
  position: relative;
  height: 100%;
  min-width: 880px;
}

.piano-key {
  position: absolute;
  top: 0;
  border-radius: 0 0 3px 3px;
  padding: 0;
  transition: background-color 0.12s ease, opacity 0.8s ease, box-shadow 0.3s ease;
  touch-action: none;
}

.piano-key.is-white {
  height: 100%;
  background: linear-gradient(to bottom, #ded3bc, var(--ivory) 12%, #d8cbb0);
  border: 1px solid #2a241d;
  z-index: 1;
}

.piano-key.is-black {
  height: 62%;
  background: linear-gradient(to bottom, #333, #100d0e 80%);
  border: 1px solid #000;
  z-index: 2;
  box-shadow: 0 3px 5px rgba(0, 0, 0, 0.6);
}

.piano-key.is-white.is-down {
  background: linear-gradient(to bottom, var(--accent), color-mix(in srgb, var(--accent) 78%, #000));
  box-shadow: inset 0 -4px 12px rgba(0, 0, 0, 0.3);
}

.piano-key.is-black.is-down {
  background: var(--accent);
}

/* Keys outside the current era's compass: not yet invented */
.piano-key.is-ghost {
  opacity: 0.13;
  pointer-events: none;
}

.piano-key .key-hint {
  position: absolute;
  bottom: 7px;
  left: 50%;
  transform: translateX(-50%);
  font-family: var(--font-mono);
  font-size: 0.55rem;
  color: rgba(20, 16, 12, 0.55);
  pointer-events: none;
}

.piano-key.is-black .key-hint { color: rgba(237, 227, 205, 0.5); bottom: 5px; }

/* Middle-C marker helps orientation as ranges shift */
.piano-key.is-middle-c::after {
  content: '';
  position: absolute;
  bottom: 22px;
  left: 50%;
  width: 4px;
  height: 4px;
  border-radius: 50%;
  transform: translateX(-50%);
  background: rgba(20, 16, 12, 0.4);
}

/* Audio toast (小提示) */
.audio-toast {
  position: fixed;
  bottom: calc(var(--dock-height) + 1rem);
  left: 50%;
  transform: translateX(-50%) translateY(8px);
  z-index: 120;
  padding: 0.5rem 1.1rem;
  font-size: 0.68rem;
  letter-spacing: 0.15em;
  color: var(--ink);
  background: color-mix(in srgb, var(--bg-soft) 94%, transparent);
  border: 1px solid var(--line);
  border-radius: 999px;
  opacity: 0;
  pointer-events: none;
  transition: opacity 0.4s ease, transform 0.4s ease;
}

.audio-toast.is-visible { opacity: 1; transform: translateX(-50%) translateY(0); }

/* --------------------------------------------------------------------------
   Responsive
   -------------------------------------------------------------------------- */
@media (max-width: 900px) {
  .chapter-body,
  .chapter-flip .chapter-body {
    grid-template-columns: 1fr;
  }

  .chapter-flip .chapter-text { order: 1; }
  .chapter-flip .chapter-figure { order: 2; }
  .chapter-figure { max-width: 30rem; }

  :root { --dock-height: 150px; }
  .dock-keys { height: 92px; }
}

@media (max-width: 600px) {
  .topbar-era { display: none; }
  .topbar-brand { letter-spacing: 0.18em; }
  .hero-sub br { display: none; }
}