:root {
  --book3d-bg: #0b0d0f;
  --book3d-panel: rgba(255,255,255,.07);
  --book3d-text: #f8f2e4;
  --book3d-muted: #c8c0ad;
  --book3d-accent: #f5d06a;
  --book3d-book-w: clamp(220px, 32vw, 370px);
  --book3d-book-h: calc(var(--book3d-book-w) * 1.5177383592);
  --book3d-depth: calc(var(--book3d-book-w) * .16);
}

* { box-sizing: border-box; }
html { scroll-behavior: smooth; }
body.book3d-page {
  margin: 0;
  min-height: 100vh;
  color: var(--book3d-text);
  background:
    radial-gradient(circle at 15% 10%, rgba(245, 208, 106, .16), transparent 28%),
    radial-gradient(circle at 80% 30%, rgba(112, 157, 255, .13), transparent 30%),
    linear-gradient(135deg, #08090b 0%, #121416 48%, #070809 100%);
  font-family: Inter, ui-sans-serif, system-ui, -apple-system, BlinkMacSystemFont, "Segoe UI", sans-serif;
  overflow-x: hidden;
}

.book3d-shell {
  width: min(1180px, calc(100% - 36px));
  margin: 0 auto;
}

.book3d-header {
  position: sticky;
  top: 0;
  z-index: 20;
  backdrop-filter: blur(18px);
  background: rgba(8,9,11,.72);
  border-bottom: 1px solid rgba(255,255,255,.08);
}
.book3d-header-inner {
  min-height: 74px;
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 24px;
}
.book3d-logo {
  text-decoration: none;
  color: var(--book3d-text);
  font-weight: 800;
  letter-spacing: .12em;
  text-transform: uppercase;
  font-size: .88rem;
}
.book3d-nav {
  display: flex;
  gap: 18px;
  flex-wrap: wrap;
  justify-content: flex-end;
}
.book3d-nav a {
  color: var(--book3d-muted);
  text-decoration: none;
  font-size: .94rem;
}
.book3d-nav a:hover,
.book3d-nav a.active { color: var(--book3d-text); }

.book3d-hero {
  min-height: calc(100vh - 74px);
  display: grid;
  grid-template-columns: minmax(0, .9fr) minmax(340px, 1.1fr);
  gap: clamp(28px, 5vw, 72px);
  align-items: center;
  padding: clamp(42px, 6vw, 78px) 0;
}
.book3d-copy h1 {
  margin: 0;
  font-family: Georgia, "Times New Roman", serif;
  font-size: clamp(3.2rem, 7vw, 6.7rem);
  line-height: .92;
  letter-spacing: -.06em;
}
.book3d-copy h1 span {
  display: block;
  color: var(--book3d-accent);
}
.book3d-copy p {
  max-width: 620px;
  margin: 26px 0 0;
  color: var(--book3d-muted);
  font-size: clamp(1.02rem, 1.35vw, 1.22rem);
  line-height: 1.65;
}
.book3d-cta-row {
  margin-top: 34px;
  display: flex;
  flex-wrap: wrap;
  gap: 14px;
}
.book3d-button {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  min-height: 46px;
  padding: 0 18px;
  border: 1px solid rgba(255,255,255,.18);
  border-radius: 999px;
  color: var(--book3d-text);
  text-decoration: none;
  background: rgba(255,255,255,.08);
}
.book3d-button.primary {
  background: var(--book3d-accent);
  color: #17130a;
  border-color: transparent;
  font-weight: 800;
}

.book3d-panel {
  position: relative;
  min-height: min(76vh, 720px);
  display: grid;
  place-items: center;
  perspective: 1500px;
  border: 1px solid rgba(255,255,255,.1);
  border-radius: 34px;
  background:
    linear-gradient(180deg, rgba(255,255,255,.08), rgba(255,255,255,.025)),
    radial-gradient(circle at 50% 45%, rgba(255,255,255,.12), transparent 40%);
  box-shadow: 0 32px 90px rgba(0,0,0,.35);
  overflow: hidden;
}
.book3d-panel::before {
  content: "";
  position: absolute;
  inset: 0;
  background: linear-gradient(120deg, rgba(255,255,255,.08), transparent 34%, rgba(245,208,106,.09) 68%, transparent);
  pointer-events: none;
}
.book3d-wrap {
  position: relative;
  width: calc(var(--book3d-book-w) + var(--book3d-depth) * 2.2);
  height: calc(var(--book3d-book-h) + 48px);
  display: grid;
  place-items: center;
  transform-style: preserve-3d;
  user-select: none;
  cursor: grab;
  touch-action: none;
}
.book3d-wrap:active { cursor: grabbing; }
.book3d-book {
  position: relative;
  width: var(--book3d-book-w);
  height: var(--book3d-book-h);
  transform-style: preserve-3d;
  transform: rotateX(0deg) rotateY(0deg);
  transition: transform .9s cubic-bezier(.2,.9,.2,1);
}
.book3d-book.is-dragging { transition: none; }
.book3d-face,
.book3d-side,
.book3d-top-bottom {
  position: absolute;
  left: 50%;
  top: 50%;
  transform-style: preserve-3d;
  background-repeat: no-repeat;
  background-position: center;
  overflow: hidden;
  backface-visibility: hidden;
  box-shadow: inset 0 0 0 1px rgba(255,255,255,.04);
}
.book3d-face {
  width: var(--book3d-book-w);
  height: var(--book3d-book-h);
  margin-left: calc(var(--book3d-book-w) / -2);
  margin-top: calc(var(--book3d-book-h) / -2);
  border-radius: 9px;
}
.book3d-front {
  background-image: var(--front-cover-image);
  background-size: 100% 100%;
  transform: translateZ(calc(var(--book3d-depth) / 2));
  box-shadow: 0 22px 56px rgba(0,0,0,.36), inset 18px 0 24px rgba(0,0,0,.28), inset -2px 0 6px rgba(255,255,255,.08);
}
.book3d-back {
  background-image: var(--back-cover-image);
  background-size: 100% 100%;
  transform: rotateY(180deg) translateZ(calc(var(--book3d-depth) / 2));
  box-shadow: inset -18px 0 26px rgba(0,0,0,.22), inset 0 0 0 1px rgba(255,255,255,.06);
}
.book3d-side {
  width: var(--book3d-depth);
  height: var(--book3d-book-h);
  margin-left: calc(var(--book3d-depth) / -2);
  margin-top: calc(var(--book3d-book-h) / -2);
  border-radius: 6px;
}
.book3d-spine {
  background-image: var(--spine-image);
  background-size: 100% 100%;
  transform: rotateY(-90deg) translateZ(calc(var(--book3d-book-w) / 2));
  box-shadow: inset 18px 0 26px rgba(255,255,255,.07), inset -16px 0 28px rgba(0,0,0,.42);
}
.book3d-pages {
  background-image: var(--pages-image);
  background-size: 100% 100%;
  transform: rotateY(90deg) translateZ(calc(var(--book3d-book-w) / 2));
  box-shadow: inset 14px 0 18px rgba(0,0,0,.22), inset -6px 0 10px rgba(255,255,255,.35);
}
.book3d-top-bottom {
  width: var(--book3d-book-w);
  height: var(--book3d-depth);
  margin-left: calc(var(--book3d-book-w) / -2);
  margin-top: calc(var(--book3d-depth) / -2);
  background-image: var(--pages-image);
  background-size: 100% 100%;
  opacity: .92;
}
.book3d-top {
  transform: rotateX(90deg) translateZ(calc(var(--book3d-book-h) / 2));
  filter: brightness(1.08);
}
.book3d-bottom {
  transform: rotateX(-90deg) translateZ(calc(var(--book3d-book-h) / 2));
  filter: brightness(.68);
}
.book3d-sheen {
  pointer-events: none;
  position: absolute;
  inset: 0;
  background: linear-gradient(106deg, rgba(255,255,255,.18) 0%, rgba(255,255,255,.03) 20%, transparent 38%, rgba(255,255,255,.12) 70%, transparent 100%);
  mix-blend-mode: screen;
  opacity: .38;
}
.book3d-shadow {
  position: absolute;
  width: calc(var(--book3d-book-w) * 1.05);
  height: 46px;
  left: 50%;
  top: calc(50% + var(--book3d-book-h) / 2 + 20px);
  transform: translateX(-50%) rotateX(78deg);
  border-radius: 50%;
  background: radial-gradient(ellipse at center, rgba(0,0,0,.52), transparent 67%);
  filter: blur(12px);
  pointer-events: none;
}
.book3d-controls {
  position: absolute;
  left: 18px;
  right: 18px;
  bottom: 18px;
  display: flex;
  gap: 8px;
  justify-content: center;
  flex-wrap: wrap;
  z-index: 5;
}
.book3d-controls button {
  border: 1px solid rgba(255,255,255,.16);
  background: rgba(0,0,0,.36);
  color: var(--book3d-text);
  border-radius: 999px;
  padding: 9px 13px;
  font: inherit;
  font-size: .86rem;
  cursor: pointer;
}
.book3d-controls button:hover { background: rgba(255,255,255,.12); }
.book3d-note {
  padding: 28px 0 60px;
  color: var(--book3d-muted);
  text-align: center;
}
.book3d-note code { color: var(--book3d-accent); }

@media (max-width: 880px) {
  .book3d-hero { grid-template-columns: 1fr; }
  .book3d-panel { min-height: 620px; }
  :root { --book3d-book-w: min(68vw, 330px); }
}
@media (max-width: 520px) {
  .book3d-nav { display: none; }
  .book3d-panel { min-height: 560px; }
  :root { --book3d-book-w: min(78vw, 288px); --book3d-depth: calc(var(--book3d-book-w) * .15); }
  .book3d-controls { bottom: 12px; }
  .book3d-controls button { padding: 8px 10px; font-size: .78rem; }
}