*, *::before, *::after {
  box-sizing: border-box;
}

body {
  font-family: system-ui, "Segoe UI", Roboto, Helvetica, Arial, sans-serif, "Apple Color Emoji", "Segoe UI Emoji", "Segoe UI Symbol";
  margin: 0;
  background: #020617;
  display: flex;
  justify-content: center;
  align-items: center;
  min-height: 100vh;
  padding: 20px;
}

.book-showcase {
  perspective: 1600px;
  display: flex;
  justify-content: center;
  align-items: center;
}

.hardcover-book {
  position: relative;
  width: 320px;
  height: 450px;
  transform-style: preserve-3d;
  transform: rotateX(30deg) rotateY(-25deg);
  transition: transform 0.6s ease;
  cursor: pointer;
}

.hardcover-book:hover {
  transform: rotateX(15deg) rotateY(-10deg);
}

.pages-block {
  position: absolute;
  top: 0;
  left: 0;
  width: 100%;
  height: 100%;
  background: #f8fafc;
  border-radius: 2px 8px 8px 2px;
  transform-style: preserve-3d;
  box-shadow: inset 10px 0 20px rgba(0,0,0,0.1), 10px 10px 30px rgba(0,0,0,0.5);
}

.pages-content {
  padding: 40px;
  height: 100%;
  display: flex;
  flex-direction: column;
  justify-content: center;
  color: #0f172a;
}

.tag {
  font-size: 0.85rem;
  font-weight: 700;
  color: #3b82f6;
  letter-spacing: 2px;
  margin-bottom: 20px;
}

.pages-content h2 {
  font-size: 2.2rem;
  margin: 0 0 16px 0;
  line-height: 1.1;
  letter-spacing: -1px;
}

.pages-content p {
  color: #475569;
  line-height: 1.6;
  margin-bottom: 40px;
}

.btn-primary {
  align-self: flex-start;
  background: #0f172a;
  color: #ffffff;
  border: none;
  padding: 12px 24px;
  border-radius: 6px;
  font-weight: 600;
  cursor: pointer;
  transition: background 0.2s;
}

.btn-primary:hover {
  background: #3b82f6;
}

/* Constructing the physical thickness of the pages */
.edge {
  position: absolute;
  background: #e2e8f0;
  /* Striped background to mimic individual pages of paper */
  background-image: repeating-linear-gradient(to bottom, #e2e8f0 0px, #e2e8f0 2px, #cbd5e1 2px, #cbd5e1 3px);
}

.right-edge {
  top: 4px;
  right: 0;
  width: 20px;
  height: calc(100% - 8px);
  transform-origin: right center;
  transform: rotateY(90deg);
}

.bottom-edge {
  bottom: 0;
  left: 4px;
  width: calc(100% - 8px);
  height: 20px;
  transform-origin: bottom center;
  transform: rotateX(-90deg);
  background-image: repeating-linear-gradient(to right, #e2e8f0 0px, #e2e8f0 2px, #cbd5e1 2px, #cbd5e1 3px);
}

/* The Cover Logic */
.front-cover {
  position: absolute;
  top: 0;
  left: 0;
  width: 100%;
  height: 100%;
  transform-origin: 0 50%;
  transform-style: preserve-3d;
  /* Sit directly on top of the 20px thick pages */
  transform: translateZ(21px);
  /* CRITICAL FIX: The cubic-bezier 0.2, 0.8, 0.2, 1 guarantees NO OVERSHOOT when returning to 0 */
  transition: transform 0.8s cubic-bezier(0.2, 0.8, 0.2, 1);
  z-index: 10;
}

.hardcover-book:hover .front-cover {
  transform: translateZ(21px) rotateY(-160deg);
}

/* Dual-sided cover geometry */
.cover-side {
  position: absolute;
  top: -2px;
  left: -2px;
  /* Slightly larger than pages for hardcover overhang */
  width: calc(100% + 6px);
  height: calc(100% + 4px);
  border-radius: 4px 12px 12px 4px;
  backface-visibility: hidden;
}

.cover-outside {
  background: #0f172a;
  color: #ffffff;
  box-shadow: inset 8px 0 20px rgba(0,0,0,0.8), 5px 5px 15px rgba(0,0,0,0.5);
  border-left: 2px solid #1e293b;
  transform: translateZ(1px);
}

.cover-design {
  padding: 40px;
  height: 100%;
  display: flex;
  flex-direction: column;
  justify-content: space-between;
  background: linear-gradient(135deg, rgba(59, 130, 246, 0.15), transparent);
}

.logo-mark {
  color: #3b82f6;
}

.cover-titles h1 {
  font-size: 3rem;
  margin: 0;
  letter-spacing: 4px;
}

.cover-titles p {
  margin: 10px 0 0 0;
  color: #94a3b8;
  letter-spacing: 2px;
  font-size: 0.9rem;
}

.cover-inside {
  background: #1e293b;
  transform: rotateY(180deg) translateZ(1px);
  box-shadow: inset -8px 0 20px rgba(0,0,0,0.8);
  display: flex;
  justify-content: center;
  align-items: center;
}

.inside-pattern {
  width: 80%;
  height: 80%;
  border: 1px solid rgba(255,255,255,0.05);
  background-image: radial-gradient(rgba(255,255,255,0.05) 1px, transparent 1px);
  background-size: 10px 10px;
}