/* ==========================================================================
   VISOR LIBRO - MÁXIMO REALISMO FÍSICO 3D Y ACÚSTICA INMERSIVA
   ========================================================================== */

:root {
  --bg-gradient: radial-gradient(ellipse at 50% 35%, #242730 0%, #14161a 50%, #090a0d 100%);
  --paper-bg: #faf8f5;
  --spine-crease-width: 68px;
  --book-shadow-ambient: 0 40px 90px -15px rgba(0, 0, 0, 0.85),
                         0 20px 45px -10px rgba(0, 0, 0, 0.70),
                         0 0 130px rgba(0, 0, 0, 0.50);
}

*, *::before, *::after {
  box-sizing: border-box;
  margin: 0;
  padding: 0;
  -webkit-tap-highlight-color: transparent;
}

html, body {
  width: 100%;
  height: 100%;
  overflow: hidden;
  background: #08090c;
  font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, Oxygen, Ubuntu, Cantarell, sans-serif;
  user-select: none;
  -webkit-user-select: none;
}

/* ==========================================================================
   ESCENARIO AMBIENTAL (MESA DE ESTUDIO CON LUZ CENITAL SUAVE)
   ========================================================================== */

.viewport-stage {
  position: relative;
  width: 100vw;
  height: 100vh;
  display: flex;
  align-items: center;
  justify-content: center;
  background: var(--bg-gradient);
  perspective: 2600px;
  overflow: hidden;
}

/* Microtextura ambiental de madera noble / escritorio oscuro */
.viewport-stage::before {
  content: "";
  position: absolute;
  top: 0;
  left: 0;
  right: 0;
  bottom: 0;
  background-image: radial-gradient(circle at 50% 30%, rgba(255, 255, 255, 0.04) 0%, transparent 60%);
  pointer-events: none;
  z-index: 0;
}

/* ==========================================================================
   CONTENEDOR DE ZOOM Y PANEO
   ========================================================================== */

.zoom-container {
  position: relative;
  width: 100%;
  height: 100%;
  display: flex;
  align-items: center;
  justify-content: center;
  transform-origin: center center;
  will-change: transform;
  transition: transform 0.08s ease-out;
  z-index: 1;
}

.zoom-container.is-zoomed {
  cursor: grab;
}

.zoom-container.is-zoomed:active {
  cursor: grabbing;
}

/* ==========================================================================
   ENVOLTORIO DEL LIBRO FÍSICO Y ELEMENTOS SKEUOMÓRFICOS
   ========================================================================== */

.book-wrapper {
  position: relative;
  display: flex;
  align-items: center;
  justify-content: center;
  will-change: transform;
}

/* Sombra ambiental de contacto sobre la mesa */
.book-ambient-shadow {
  position: absolute;
  top: 3%;
  left: -2%;
  width: 104%;
  height: 97%;
  box-shadow: var(--book-shadow-ambient);
  border-radius: 8px;
  pointer-events: none;
  z-index: 0;
  transition: left 0.4s cubic-bezier(0.25, 1, 0.5, 1),
              width 0.4s cubic-bezier(0.25, 1, 0.5, 1),
              opacity 0.4s ease;
}

/* Sombra central del lomo en contacto con la mesa */
.book-spine-crease-shadow {
  position: absolute;
  top: 1%;
  left: 50%;
  width: 28px;
  height: 98%;
  transform: translateX(-50%);
  background: radial-gradient(ellipse at center, rgba(0, 0, 0, 0.95) 0%, rgba(0, 0, 0, 0.4) 60%, transparent 90%);
  filter: blur(4px);
  pointer-events: none;
  z-index: 1;
  opacity: 0.9;
  transition: opacity 0.4s ease;
}

/* ==========================================================================
   BASE DE TAPA DURA (CARCASA QUE SOBRESALE DEL PAPEL - CEJA DE LA TAPA)
   ========================================================================== */

.book-hardcover-base {
  position: absolute;
  top: -5px;
  left: -6px;
  width: calc(100% + 12px);
  height: calc(100% + 10px);
  background: linear-gradient(135deg, #1b1d22 0%, #111215 50%, #0d0e11 100%);
  border-radius: 8px;
  box-shadow: 0 10px 30px rgba(0, 0, 0, 0.7),
              inset 0 0 0 1px rgba(255, 255, 255, 0.07),
              inset 0 1px 2px rgba(255, 255, 255, 0.12);
  pointer-events: none;
  z-index: 1;
  transition: all 0.4s cubic-bezier(0.25, 1, 0.5, 1);
}

/* Cabezada bordada tradicional (tela visible en los extremos superior e inferior del lomo) */
.hardcover-spine-head,
.hardcover-spine-tail {
  position: absolute;
  left: 50%;
  width: 26px;
  height: 5px;
  transform: translateX(-50%);
  background: repeating-linear-gradient(
    to right,
    #9c2727 0px,
    #9c2727 2px,
    #f1dfa8 2px,
    #f1dfa8 4px
  );
  border-radius: 2px;
  box-shadow: 0 1px 3px rgba(0, 0, 0, 0.7);
  z-index: 2;
  transition: opacity 0.4s ease;
}

.hardcover-spine-head {
  top: -2px;
}

.hardcover-spine-tail {
  bottom: -2px;
}

/* ==========================================================================
   BLOQUES Y CANTOS DE HOJAS FÍSICAS (PÁGINAS APILADAS CON PERSPECTIVA)
   ========================================================================== */

/* Cantos superior e inferior del bloque de hojas */
.book-edge-stack {
  position: absolute;
  left: 2px;
  width: calc(100% - 4px);
  height: 4px;
  background: repeating-linear-gradient(
    to right,
    #ded7c9 0px,
    #c5baa7 1px,
    #efeae0 2px,
    #bbb09e 3px
  );
  box-shadow: 0 0 4px rgba(0, 0, 0, 0.3) inset;
  pointer-events: none;
  z-index: 2;
  opacity: 0.9;
}

.book-edge-top {
  top: -3px;
  border-radius: 2px 2px 0 0;
  background: linear-gradient(to right, #ccc4b4 0%, #eee8dc 45%, #9c917f 50%, #eee8dc 55%, #ccc4b4 100%);
}

.book-edge-bottom {
  bottom: -3px;
  border-radius: 0 0 2px 2px;
  background: linear-gradient(to right, #ccc4b4 0%, #eee8dc 45%, #9c917f 50%, #eee8dc 55%, #ccc4b4 100%);
}

/* Espesor lateral (fore-edge con páginas apiladas y sombra 3D) */
.book-side-thickness {
  position: absolute;
  top: 1px;
  bottom: 1px;
  width: 12px;
  pointer-events: none;
  z-index: 3;
  opacity: 0.92;
  transition: opacity 0.3s ease, width 0.3s ease;
}

.book-thickness-left {
  left: -11px;
  background: repeating-linear-gradient(
    to bottom,
    #f2ede4 0px,
    #d1c6b5 1px,
    #e8e1d5 2px,
    #b9ac98 3px
  );
  box-shadow: -4px 0 8px rgba(0, 0, 0, 0.45) inset,
              -6px 6px 14px rgba(0, 0, 0, 0.6);
  border-radius: 3px 0 0 3px;
  transform: perspective(600px) rotateY(18deg);
}

.book-thickness-right {
  right: -11px;
  background: repeating-linear-gradient(
    to bottom,
    #f2ede4 0px,
    #d1c6b5 1px,
    #e8e1d5 2px,
    #b9ac98 3px
  );
  box-shadow: 4px 0 8px rgba(0, 0, 0, 0.45) inset,
              6px 6px 14px rgba(0, 0, 0, 0.6);
  border-radius: 0 3px 3px 0;
  transform: perspective(600px) rotateY(-18deg);
}

/* ==========================================================================
   CONTENEDOR CENTRAL DE STPAGEFLIP
   ========================================================================== */

.book-flip-container {
  position: relative;
  z-index: 4;
}

/* ==========================================================================
   ESTRUCTURA Y DETALLES DE CADA PÁGINA
   ========================================================================== */

.page {
  position: absolute;
  background-color: var(--paper-bg);
  overflow: hidden;
  box-shadow: 0 0 2px rgba(0, 0, 0, 0.2);
}

.page-content {
  position: relative;
  width: 100%;
  height: 100%;
  overflow: hidden;
  display: flex;
  align-items: center;
  justify-content: center;
  background-color: var(--paper-bg);
}

/* Canvas del PDF */
.page-canvas {
  width: 100%;
  height: 100%;
  object-fit: contain;
  display: block;
  user-select: none;
  pointer-events: none;
  z-index: 1;
}

/* ==========================================================================
   TEXTURA DE PAPEL TÁCTIL Y GRANO ÓPTICO (MIX-BLEND MULTIPLY)
   ========================================================================== */

.page-paper-grain {
  position: absolute;
  top: 0;
  left: 0;
  right: 0;
  bottom: 0;
  background: radial-gradient(ellipse at 50% 50%, rgba(255, 255, 255, 0.05) 0%, rgba(0, 0, 0, 0.02) 100%);
  pointer-events: none;
  z-index: 8;
  mix-blend-mode: multiply;
}

/* ==========================================================================
   SOMBRAS PROFUNDAS DEL LOMO (CANALÓN CENTRAL) Y ARCO DE PAPEL
   ========================================================================== */

/* Sombra profunda y tangible del canalón en la página izquierda */
.page.--left .page-spine-shadow {
  position: absolute;
  top: 0;
  right: 0;
  bottom: 0;
  width: var(--spine-crease-width);
  background: linear-gradient(
    to right,
    rgba(0, 0, 0, 0) 0%,
    rgba(0, 0, 0, 0.03) 45%,
    rgba(0, 0, 0, 0.10) 75%,
    rgba(0, 0, 0, 0.26) 92%,
    rgba(0, 0, 0, 0.44) 98%,
    rgba(0, 0, 0, 0.52) 100%
  );
  pointer-events: none;
  z-index: 12;
}

/* Sombra profunda y tangible del canalón en la página derecha */
.page.--right .page-spine-shadow {
  position: absolute;
  top: 0;
  left: 0;
  bottom: 0;
  width: var(--spine-crease-width);
  background: linear-gradient(
    to left,
    rgba(0, 0, 0, 0) 0%,
    rgba(0, 0, 0, 0.03) 45%,
    rgba(0, 0, 0, 0.10) 75%,
    rgba(0, 0, 0, 0.26) 92%,
    rgba(0, 0, 0, 0.44) 98%,
    rgba(0, 0, 0, 0.52) 100%
  );
  pointer-events: none;
  z-index: 12;
}

/* Reflejo cilíndrico en el arco curvado de la hoja junto al lomo */
.page.--left .page-curl-arch {
  position: absolute;
  top: 0;
  right: calc(var(--spine-crease-width) * 0.85);
  bottom: 0;
  width: 48px;
  background: linear-gradient(
    to right,
    transparent 0%,
    rgba(255, 255, 255, 0.05) 50%,
    rgba(255, 255, 255, 0.10) 80%,
    transparent 100%
  );
  pointer-events: none;
  z-index: 11;
}

.page.--right .page-curl-arch {
  position: absolute;
  top: 0;
  left: calc(var(--spine-crease-width) * 0.85);
  bottom: 0;
  width: 48px;
  background: linear-gradient(
    to left,
    transparent 0%,
    rgba(255, 255, 255, 0.05) 50%,
    rgba(255, 255, 255, 0.10) 80%,
    transparent 100%
  );
  pointer-events: none;
  z-index: 11;
}

/* Iluminación cenital y caída de luz a lo largo del pliego */
.page.--left .page-lighting-glow {
  position: absolute;
  top: 0;
  left: 0;
  right: var(--spine-crease-width);
  bottom: 0;
  background: linear-gradient(
    to right,
    rgba(255, 255, 255, 0.03) 0%,
    rgba(255, 255, 255, 0.01) 60%,
    rgba(0, 0, 0, 0.015) 100%
  );
  pointer-events: none;
  z-index: 9;
}

.page.--right .page-lighting-glow {
  position: absolute;
  top: 0;
  left: var(--spine-crease-width);
  right: 0;
  bottom: 0;
  background: linear-gradient(
    to left,
    rgba(255, 255, 255, 0.03) 0%,
    rgba(255, 255, 255, 0.01) 60%,
    rgba(0, 0, 0, 0.015) 100%
  );
  pointer-events: none;
  z-index: 9;
}

/* Sombra interior en esquinas superior e inferior hacia la encuadernación */
.page.--left .page-corner-gutter-shadow {
  position: absolute;
  top: 0;
  right: 0;
  width: 90px;
  height: 100%;
  background: radial-gradient(ellipse at 100% 0%, rgba(0, 0, 0, 0.16) 0%, transparent 60%),
              radial-gradient(ellipse at 100% 100%, rgba(0, 0, 0, 0.16) 0%, transparent 60%);
  pointer-events: none;
  z-index: 10;
}

.page.--right .page-corner-gutter-shadow {
  position: absolute;
  top: 0;
  left: 0;
  width: 90px;
  height: 100%;
  background: radial-gradient(ellipse at 0% 0%, rgba(0, 0, 0, 0.16) 0%, transparent 60%),
              radial-gradient(ellipse at 0% 100%, rgba(0, 0, 0, 0.16) 0%, transparent 60%);
  pointer-events: none;
  z-index: 10;
}

/* Bisel fino y borde físico de corte del papel en el extremo exterior */
.page.--left .page-outer-edge {
  position: absolute;
  top: 0;
  left: 0;
  bottom: 0;
  width: 14px;
  background: linear-gradient(to right, rgba(0, 0, 0, 0.16) 0%, rgba(0, 0, 0, 0.04) 50%, transparent 100%);
  box-shadow: inset -1px 0 0 rgba(255, 255, 255, 0.35);
  pointer-events: none;
  z-index: 12;
}

.page.--right .page-outer-edge {
  position: absolute;
  top: 0;
  right: 0;
  bottom: 0;
  width: 14px;
  background: linear-gradient(to left, rgba(0, 0, 0, 0.16) 0%, rgba(0, 0, 0, 0.04) 50%, transparent 100%);
  box-shadow: inset 1px 0 0 rgba(255, 255, 255, 0.35);
  pointer-events: none;
  z-index: 12;
}

/* ==========================================================================
   DETALLES DE TAPA DURA EN PORTADA Y CONTRAPORTADA
   ========================================================================== */

.page.--hard {
  box-shadow: 0 6px 22px rgba(0, 0, 0, 0.45);
}

.page-cover-front {
  border-radius: 2px 7px 7px 2px;
}

.page-cover-back {
  border-radius: 7px 2px 2px 7px;
}

/* Hendidura física de la bisagra de la tapa dura (ranura de articulación a 22px del lomo) */
.page-cover-front .page-cover-hinge-crease {
  position: absolute;
  top: 0;
  left: 22px;
  bottom: 0;
  width: 4px;
  background: linear-gradient(to right, rgba(0,0,0,0.22) 0%, rgba(255,255,255,0.08) 50%, rgba(0,0,0,0.18) 100%);
  box-shadow: 0 0 2px rgba(0,0,0,0.4);
  pointer-events: none;
  z-index: 13;
}

.page-cover-back .page-cover-hinge-crease {
  position: absolute;
  top: 0;
  right: 22px;
  bottom: 0;
  width: 4px;
  background: linear-gradient(to left, rgba(0,0,0,0.22) 0%, rgba(255,255,255,0.08) 50%, rgba(0,0,0,0.18) 100%);
  box-shadow: 0 0 2px rgba(0,0,0,0.4);
  pointer-events: none;
  z-index: 13;
}

/* Brillo y relieve sutil en tapas duras */
.page-cover-sheen {
  position: absolute;
  top: 0;
  left: 0;
  right: 0;
  bottom: 0;
  background: linear-gradient(135deg, rgba(255,255,255,0.06) 0%, transparent 45%, rgba(0,0,0,0.08) 100%);
  box-shadow: inset 0 0 0 1px rgba(255, 255, 255, 0.12),
              inset 0 0 15px rgba(0, 0, 0, 0.25);
  pointer-events: none;
  z-index: 14;
}

/* ==========================================================================
   ZONAS DE CLIC EN EXTREMOS PARA NAVEGACIÓN TÁCTIL Y DE RATÓN
   ========================================================================== */

.edge-click-zone {
  position: fixed;
  top: 0;
  bottom: 0;
  width: 7vw;
  min-width: 50px;
  max-width: 110px;
  z-index: 20;
  background: transparent;
  border: none;
  outline: none;
  cursor: pointer;
  opacity: 0;
  transition: opacity 0.3s ease;
}

.edge-left {
  left: 0;
}

.edge-right {
  right: 0;
}

.edge-left:hover {
  cursor: w-resize;
}

.edge-right:hover {
  cursor: e-resize;
}

/* ==========================================================================
   INDICADOR DE CARGA ULTRA-MINIMALISTA CON BARRA DE PROGRESO
   ========================================================================== */

.loader-overlay {
  position: fixed;
  top: 0;
  left: 0;
  width: 100vw;
  height: 100vh;
  display: flex;
  align-items: center;
  justify-content: center;
  background: #08090b;
  z-index: 100;
  transition: opacity 0.5s cubic-bezier(0.16, 1, 0.3, 1), visibility 0.5s;
}

.loader-overlay.is-hidden {
  opacity: 0;
  visibility: hidden;
  pointer-events: none;
}

.loader-box {
  display: flex;
  flex-direction: column;
  align-items: center;
  justify-content: center;
  gap: 22px;
}

.loader-status {
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: 10px;
  width: 220px;
}

.loader-progress-track {
  width: 100%;
  height: 3px;
  background: rgba(255, 255, 255, 0.12);
  border-radius: 4px;
  overflow: hidden;
}

.loader-progress-bar {
  width: 0%;
  height: 100%;
  background: #e2ddd3;
  border-radius: 4px;
  transition: width 0.2s ease-out;
  box-shadow: 0 0 10px rgba(226, 221, 211, 0.6);
}

.loader-status-text {
  font-size: 13px;
  font-weight: 400;
  color: #a4a29d;
  letter-spacing: 0.5px;
  margin: 0;
  text-align: center;
  font-family: inherit;
}

.book-loader-spine {
  position: relative;
  width: 60px;
  height: 44px;
  perspective: 200px;
}

.loader-page {
  position: absolute;
  top: 0;
  left: 30px;
  width: 30px;
  height: 44px;
  background: #e2ddd3;
  border-radius: 0 2px 2px 0;
  transform-origin: left center;
  box-shadow: 0 2px 6px rgba(0, 0, 0, 0.4);
}

.loader-page-1 {
  animation: flipLoaderPage 1.6s infinite ease-in-out;
}

.loader-page-2 {
  animation: flipLoaderPage 1.6s infinite ease-in-out 0.25s;
}

.loader-page-3 {
  animation: flipLoaderPage 1.6s infinite ease-in-out 0.5s;
}

@keyframes flipLoaderPage {
  0% {
    transform: rotateY(0deg);
    opacity: 1;
  }
  50% {
    transform: rotateY(-180deg);
    opacity: 0.8;
  }
  100% {
    transform: rotateY(-180deg);
    opacity: 0;
  }
}

/* ==========================================================================
   BOTÓN FLOTANTE DE PANTALLA COMPLETA ELEGANTE Y DISCRETO
   ========================================================================== */

.fullscreen-toggle-btn {
  position: fixed;
  top: 18px;
  right: 18px;
  width: 44px;
  height: 44px;
  border-radius: 50%;
  background: rgba(18, 20, 26, 0.45);
  backdrop-filter: blur(12px);
  -webkit-backdrop-filter: blur(12px);
  border: 1px solid rgba(255, 255, 255, 0.12);
  color: #dcd8d0;
  display: flex;
  align-items: center;
  justify-content: center;
  cursor: pointer;
  z-index: 60;
  opacity: 0.55;
  transition: opacity 0.25s ease, background 0.25s ease, transform 0.2s cubic-bezier(0.16, 1, 0.3, 1), border-color 0.25s ease;
  box-shadow: 0 4px 15px rgba(0, 0, 0, 0.4);
  outline: none;
}

.fullscreen-toggle-btn:hover {
  opacity: 1;
  background: rgba(28, 31, 38, 0.85);
  border-color: rgba(255, 255, 255, 0.28);
  color: #ffffff;
  transform: scale(1.08);
  box-shadow: 0 6px 20px rgba(0, 0, 0, 0.6);
}

.fullscreen-toggle-btn:active {
  transform: scale(0.95);
}

.fullscreen-toggle-btn .icon-compress {
  display: none;
}

body.is-fullscreen .fullscreen-toggle-btn .icon-expand {
  display: none;
}

body.is-fullscreen .fullscreen-toggle-btn .icon-compress {
  display: block;
}

/* ==========================================================================
   OPTIMIZACIONES PARA BAJOS RECURSOS Y RENDIMIENTO DE GPU (HARDWARE ACCEL)
   ========================================================================== */

.page {
  contain: layout paint style;
  backface-visibility: hidden;
  -webkit-backface-visibility: hidden;
  transform: translateZ(0);
}

.page-content {
  contain: layout paint;
  transform: translateZ(0);
}

.page-canvas {
  contain: strict;
  image-rendering: -webkit-optimize-contrast;
}

/* ==========================================================================
   RESPONSIVIDAD Y OPTIMIZACIÓN MULTIDISPOSITIVO
   ========================================================================== */

@media (max-width: 768px) {
  :root {
    --spine-crease-width: 38px;
  }
  .book-side-thickness,
  .book-edge-stack,
  .book-hardcover-base {
    display: none;
  }
  .edge-click-zone {
    width: 12vw;
  }
  .fullscreen-toggle-btn {
    top: 12px;
    right: 12px;
    width: 40px;
    height: 40px;
  }
}