:root {
  /* Cubierta de cuero (portada, barra superior, cajón de índice) */
  --cover: #5c2a2a;
  --cover-deep: #3e1c1c;
  --cover-ink: #f2e9da;

  /* Papel (páginas del libro) */
  --paper: #f8f3e8;
  --paper-2: #efe6d3;
  --ink: #2a2420;
  --muted: #79695c;
  --line: rgba(42, 36, 32, .14);

  /* Hilo — único acento cálido, usado con moderación */
  --thread: #a3792f;
  --thread-soft: #d8c093;

  --shadow: 0 24px 60px rgba(20, 10, 6, .22);
  --serif: "Spectral", Georgia, serif;
  --sans: "Work Sans", system-ui, sans-serif;
}

* { box-sizing: border-box; }
html { scroll-behavior: smooth; }
body {
  margin: 0;
  min-height: 100vh;
  background: var(--cover-deep);
  color: var(--ink);
  font-family: var(--sans);
  overflow-x: hidden;
}
button { font: inherit; }
button:focus-visible, textarea:focus-visible, a:focus-visible { outline: 2px solid var(--thread); outline-offset: 3px; }
@media (prefers-reduced-motion: reduce) {
  html { scroll-behavior: auto; }
  * { animation-duration: .001ms !important; transition-duration: .001ms !important; }
}

/* ---------- Barra superior ---------- */
.topbar {
  position: fixed;
  top: 0; left: 0; right: 0;
  height: 60px;
  padding: 0 20px;
  display: flex;
  align-items: center;
  justify-content: space-between;
  z-index: 50;
  color: var(--cover-ink);
  background: transparent;
  transition: background .3s ease;
}
.topbar.scrolled { background: rgba(37, 17, 17, .92); backdrop-filter: blur(10px); }
.brand-mini { font: 500 13px var(--serif); font-style: italic; opacity: .92; }
.top-actions { display: flex; align-items: center; gap: 10px; }
.counter { font-size: 12px; opacity: .75; min-width: 45px; text-align: right; }
.icon-btn {
  border: 1px solid rgba(242, 233, 218, .25);
  background: rgba(242, 233, 218, .07);
  color: var(--cover-ink);
  width: 36px; height: 36px;
  border-radius: 50%;
  cursor: pointer;
  display: grid;
  place-items: center;
  transition: background .2s;
}
.icon-btn:hover { background: rgba(242, 233, 218, .16); }

/* ---------- Portada ---------- */
.cover {
  min-height: 100svh;
  position: relative;
  display: grid;
  place-items: center;
  padding: 90px 7vw 60px;
  color: var(--cover-ink);
  background: var(--cover);
}
.cover-grid {
  width: min(1100px, 100%);
  display: grid;
  grid-template-columns: 1fr .82fr;
  gap: 6vw;
  align-items: center;
}
.cover-kicker {
  font: 500 14px var(--serif);
  font-style: italic;
  color: var(--thread-soft);
}
.cover h1 {
  margin: 14px 0 20px;
  font: 500 clamp(38px, 4.6vw, 60px)/1.08 var(--serif);
  letter-spacing: -.01em;
  max-width: 11ch;
}
.cover-subtitle {
  max-width: 46ch;
  color: rgba(242, 233, 218, .78);
  font-size: 16px;
  line-height: 1.7;
}
.primary-btn {
  margin-top: 28px;
  border: 1px solid rgba(242, 233, 218, .5);
  border-radius: 3px;
  padding: 13px 26px;
  color: var(--cover-ink);
  background: transparent;
  cursor: pointer;
  font: 500 14px var(--sans);
  letter-spacing: .01em;
  transition: background .2s, color .2s;
}
.primary-btn:hover { background: var(--cover-ink); color: var(--cover-deep); }

.cover-plate { display: flex; justify-content: center; }
.plate-frame {
  margin: 0;
  width: min(340px, 100%);
  padding: 14px 14px 20px;
  background: var(--paper);
  border-radius: 2px;
  box-shadow: var(--shadow);
  transform: rotate(1.2deg);
}
.plate-photo {
  display: block;
  width: 100%;
  aspect-ratio: 3 / 4;
  object-fit: cover;
  filter: sepia(.08) saturate(.92);
}
.plate-frame figcaption {
  margin-top: 14px;
  text-align: center;
  font: italic 400 16px var(--serif);
  color: var(--muted);
}

/* ---------- Lector / libro ---------- */
.reader {
  min-height: 100svh;
  padding: 100px 4vw 70px;
  display: grid;
  place-items: center;
  background: var(--paper-2);
}
.reader-shell { width: min(1150px, 100%); }
.book {
  width: 100%;
  min-height: 620px;
  display: grid;
  grid-template-columns: 1fr 10px 1fr;
  filter: drop-shadow(0 28px 40px rgba(30, 20, 12, .18));
}
.page {
  position: relative;
  overflow: hidden;
  padding: 64px clamp(26px, 4.5vw, 72px);
  background: var(--paper);
}
.page-left { border-radius: 5px 0 0 5px; }
.page-right { border-radius: 0 5px 5px 0; }
.book-spine {
  background: linear-gradient(90deg, #d6cab0, #f4eddf 45%, #c2b494);
  box-shadow: inset 0 0 8px rgba(0, 0, 0, .14);
}
.page-content { position: relative; z-index: 2; }
.page-kicker {
  display: block;
  color: var(--thread);
  font: 600 11px var(--sans);
  letter-spacing: .04em;
  margin-bottom: 10px;
}
.page h2 {
  margin: 0 0 22px;
  font: 500 clamp(28px, 3vw, 42px)/1.12 var(--serif);
  color: var(--ink);
}
.page p {
  margin: 0 0 15px;
  font: 15px/1.75 var(--serif);
  color: #46403a;
}
.page .quote {
  margin: 22px 0;
  padding: 14px 0 14px 18px;
  border-left: 2px solid var(--thread-soft);
  color: var(--ink);
  font: italic 400 19px/1.4 var(--serif);
}
.section-title {
  font: 600 11px var(--sans);
  letter-spacing: .04em;
  color: var(--thread);
  margin: 24px 0 10px;
}
.question {
  padding: 14px 0 16px;
  border-bottom: 1px solid var(--line);
}
.question:last-child { border-bottom: 0; }
.question strong {
  display: block;
  font: 500 18px/1.35 var(--serif);
  color: var(--ink);
  margin-bottom: 8px;
}
.page-number {
  position: absolute;
  bottom: 24px;
  color: #a79e8f;
  font: 11px var(--sans);
  z-index: 2;
}
.page-left .page-number { left: 44px; }
.page-right .page-number { right: 44px; }

.reader-controls {
  display: grid;
  grid-template-columns: 1fr auto 1fr;
  align-items: center;
  gap: 18px;
  margin-top: 26px;
}
.nav-btn {
  justify-self: start;
  border: 1px solid rgba(42, 36, 32, .22);
  background: rgba(255, 255, 255, .5);
  color: var(--ink);
  border-radius: 3px;
  padding: 10px 16px;
  cursor: pointer;
  transition: background .2s;
}
.nav-btn:last-child { justify-self: end; }
.nav-btn:hover:not(:disabled) { background: white; }
.nav-btn:disabled { opacity: .35; cursor: not-allowed; }
.page-dots { display: flex; gap: 5px; justify-content: center; flex-wrap: wrap; max-width: 420px; }
.dot { width: 6px; height: 6px; border: 0; border-radius: 50%; padding: 0; background: #c4b89e; cursor: pointer; }
.dot.active { background: var(--thread); transform: scale(1.4); }

.mobile-page { display: none; }

/* ---------- Cajón de índice ---------- */
.drawer {
  position: fixed;
  z-index: 100;
  top: 0; bottom: 0; left: 0;
  width: min(400px, 92vw);
  background: var(--paper);
  transform: translateX(-105%);
  transition: transform .35s cubic-bezier(.2, .8, .2, 1);
  box-shadow: 20px 0 50px rgba(0, 0, 0, .22);
  padding: 26px;
  overflow-y: auto;
}
.drawer.open { transform: translateX(0); }
.drawer-backdrop {
  position: fixed; inset: 0; z-index: 90;
  background: rgba(20, 10, 6, .45);
  opacity: 0; pointer-events: none;
  transition: .3s;
}
.drawer-backdrop.open { opacity: 1; pointer-events: auto; }
.drawer-head { display: flex; justify-content: space-between; align-items: flex-start; }
.drawer .icon-btn { color: var(--ink); border-color: var(--line); background: transparent; }
.drawer-kicker { font: italic 500 13px var(--serif); color: var(--thread); }
.drawer h2 { margin: 4px 0 0; font: 500 32px var(--serif); color: var(--ink); }
.progress-wrap { margin: 26px 0 22px; }
.progress-meta { display: flex; justify-content: space-between; font: 12px var(--sans); color: var(--muted); margin-bottom: 7px; }
.progress { height: 4px; background: #ddd2ba; border-radius: 10px; overflow: hidden; }
.progress span { display: block; height: 100%; width: 0; background: var(--thread); transition: width .35s; }
.lesson-nav button {
  width: 100%; text-align: left;
  border: 0; background: transparent;
  padding: 11px 9px;
  border-radius: 4px;
  color: #453e35;
  font: 14px var(--sans);
  cursor: pointer;
  transition: background .2s;
}
.lesson-nav button:hover, .lesson-nav button.active { background: rgba(163, 121, 47, .12); color: var(--ink); }
.lesson-nav .unit {
  padding: 16px 9px 6px;
  color: var(--thread);
  font: 600 11px var(--sans);
  letter-spacing: .02em;
}
.lesson-nav .num { font-weight: 600; color: var(--thread); margin-right: 7px; }

.toast {
  position: fixed;
  right: 20px; bottom: 20px;
  z-index: 200;
  padding: 10px 14px;
  border-radius: 4px;
  color: var(--cover-ink);
  background: var(--cover-deep);
  font: 12px var(--sans);
  opacity: 0; transform: translateY(10px);
  pointer-events: none;
  transition: .25s;
}
.toast.show { opacity: 1; transform: none; }

/* ---------- Ventana para pedir la clave de guardado ---------- */
.modal-backdrop {
  position: fixed; inset: 0; z-index: 300;
  background: rgba(20, 10, 6, .55);
  display: none;
  align-items: center;
  justify-content: center;
  padding: 20px;
}
.modal-backdrop.open { display: flex; }
.modal-backdrop .modal {
  background: var(--paper);
  border-radius: 8px;
  padding: 22px;
  width: min(340px, 100%);
  box-shadow: var(--shadow);
}
.modal-backdrop h3 { margin: 0 0 8px; font: 500 20px var(--serif); color: var(--ink); }
.modal-backdrop p { margin: 0 0 14px; font: 13px/1.5 var(--sans); color: var(--muted); }
.modal-backdrop input[type="password"] {
  width: 100%;
  padding: 10px 12px;
  border: 1px solid var(--line);
  border-radius: 5px;
  font: 14px var(--sans);
  margin-bottom: 16px;
  background: white;
  color: var(--ink);
}
.modal-actions { display: flex; justify-content: flex-end; gap: 10px; }
.modal-btn-ghost, .modal-btn-solid {
  border-radius: 4px;
  padding: 9px 16px;
  font: 500 13px var(--sans);
  cursor: pointer;
}
.modal-btn-ghost { background: transparent; border: 1px solid var(--line); color: var(--ink); }
.modal-btn-solid { background: var(--cover); border: 0; color: var(--cover-ink); }
.modal-btn-solid:hover { background: var(--cover-deep); }

/* ---------- Modo oscuro ---------- */
body.dark .reader { background: #241d16; }
body.dark .page { background: #f1e9d9; }
body.dark .reader-controls .nav-btn { color: var(--cover-ink); border-color: rgba(242, 233, 218, .2); background: rgba(242, 233, 218, .06); }
body.dark .drawer { background: #2c231a; color: var(--cover-ink); }
body.dark .drawer h2, body.dark .lesson-nav button { color: #f1e9d9; }
body.dark .lesson-nav button:hover, body.dark .lesson-nav button.active { background: rgba(163, 121, 47, .18); }
body.dark .progress { background: rgba(242, 233, 218, .14); }

/* ---------- Respuestas del usuario ---------- */
.answer-label {
  display: block;
  margin: 10px 0 6px;
  font: 600 10px var(--sans);
  letter-spacing: .05em;
  color: var(--thread);
}
.answer-box {
  display: block;
  width: 100%;
  min-height: 105px;
  resize: vertical;
  border: 1px solid rgba(42, 36, 32, .2);
  border-radius: 4px;
  background: rgba(255, 255, 255, .5);
  color: var(--ink);
  padding: 11px 12px;
  font: 400 13.5px/1.6 var(--sans);
  outline: none;
  transition: border-color .2s, background .2s;
}
.answer-box::placeholder { color: #a49a8c; }
.answer-box:focus { border-color: var(--thread); background: white; }
body.dark .answer-box { background: rgba(255, 255, 255, .08); color: #f1e9d9; border-color: rgba(255, 255, 255, .18); }
body.dark .answer-box:focus { background: rgba(255, 255, 255, .12); }

/* ---------- Transición de página ---------- */
.page.turn-next { animation: turnNext .5s ease; }
.page.turn-prev { animation: turnPrev .5s ease; }
@keyframes turnNext {
  0% { transform: perspective(1600px) rotateY(0); opacity: 1; }
  45% { transform: perspective(1600px) rotateY(-5deg); opacity: .6; }
  100% { transform: perspective(1600px) rotateY(0); opacity: 1; }
}
@keyframes turnPrev {
  0% { transform: perspective(1600px) rotateY(0); opacity: 1; }
  45% { transform: perspective(1600px) rotateY(5deg); opacity: .6; }
  100% { transform: perspective(1600px) rotateY(0); opacity: 1; }
}

/* ---------- Tablet / escritorio angosto ---------- */
@media (max-width: 1000px) {
  .cover-grid { grid-template-columns: 1fr; text-align: center; gap: 30px; }
  .cover-copy { order: 1; }
  .cover h1 { max-width: none; margin-left: auto; margin-right: auto; }
  .cover-plate { order: 0; }
}

/* ---------- Móvil ---------- */
@media (max-width: 850px) {
  body { overflow-x: clip; }
  .topbar { height: 56px; padding: 0 12px; }
  .brand-mini { font-size: 12px; max-width: 46vw; overflow: hidden; text-overflow: ellipsis; white-space: nowrap; }
  .icon-btn { width: 34px; height: 34px; }

  .cover { min-height: auto; padding: 80px 20px 40px; }
  .cover h1 { font-size: clamp(32px, 9vw, 44px); }
  .cover-subtitle { font-size: 14px; margin: 0 auto; }
  .plate-frame { width: min(280px, 84vw); }

  .reader { padding: 64px 10px 28px; }
  .reader-shell { width: 100%; display: flex; flex-direction: column; align-items: stretch; }
  .book-shadow, .book { display: none; }

  .mobile-page {
    order: 1;
    display: block;
    width: 100%;
    background: var(--paper);
    border-radius: 8px;
    box-shadow: 0 16px 40px rgba(20, 10, 6, .16);
    overflow: hidden;
    position: relative;
  }
  .mobile-page-top {
    display: flex;
    justify-content: space-between;
    gap: 12px;
    padding: 16px 20px 12px;
    border-bottom: 1px solid var(--line);
    color: var(--thread);
    font: 600 10px var(--sans);
    letter-spacing: .03em;
  }
  .mobile-page .page-content { padding: 26px 20px; }
  .mobile-page h2 { margin: 8px 0 18px; font: 500 clamp(28px, 8vw, 36px)/1.15 var(--serif); }
  .mobile-page .section-title { margin-top: 22px; }
  .mobile-page p { font-size: 14px; }
  .mobile-page .question strong { font-size: 16px; }
  .mobile-page .answer-box { min-height: 120px; font-size: 14px; }
  .mobile-page-bottom {
    display: block;
    padding: 12px 20px 15px;
    text-align: center;
    font: 10px var(--sans);
    color: var(--muted);
    border-top: 1px solid var(--line);
  }

  .reader-controls {
    order: 2;
    width: 100%;
    margin: 10px 0 0;
    padding: 6px;
    display: grid;
    grid-template-columns: 1fr 1fr;
    gap: 8px;
    position: sticky;
    bottom: max(10px, env(safe-area-inset-bottom));
    z-index: 20;
    border-radius: 10px;
    background: rgba(37, 17, 17, .9);
    backdrop-filter: blur(12px);
  }
  .reader-controls .nav-btn {
    width: 100%;
    min-height: 42px;
    color: var(--cover-ink);
    border-color: rgba(242, 233, 218, .2);
    background: rgba(242, 233, 218, .07);
  }
  .page-dots { display: none; }

  .drawer { width: min(92vw, 380px); padding: 20px 15px; }
  body.drawer-open { overflow: hidden; }
}