* {
  box-sizing: border-box;
}

body {
  margin: 0;
  font-family: "Segoe UI", system-ui, sans-serif;
  background: #101316;
  color: #f2f4f8;
  overflow: hidden;
}

.app {
  height: 100vh;
  width: 100vw;
}

.controls {
  display: flex;
  align-items: center;
  gap: 12px;
}

.controls button {
  border: 1px solid #2a3440;
  background: #1a222c;
  color: #f2f4f8;
  padding: 8px 16px;
  border-radius: 6px;
  cursor: pointer;
}

.controls button:disabled {
  opacity: 0.5;
  cursor: not-allowed;
}

.controls.overlay {
  position: absolute;
  top: 16px;
  right: 24px;
  background: rgba(12, 16, 22, 0.7);
  border: 1px solid #1f2a36;
  border-radius: 10px;
  padding: 8px 12px;
  z-index: 10;
}

.book {
  position: relative;
  background: #0d1117;
  border: 1px solid #1f2a36;
  border-radius: 12px;
  padding: 8px;
  display: flex;
  align-items: center;
  justify-content: center;
  height: 100%;
}

.flipbook {
  width: 100%;
  height: 100%;
  margin: 0 auto;
}

.flipbook .page {
  width: 100%;
  height: 100%;
  background: #0b0f13;
}

.flipbook .page img {
  width: 100%;
  height: 100%;
  object-fit: contain;
  display: block;
  background: #0b0f13;
}

.hint {
  position: absolute;
  bottom: 12px;
  right: 18px;
  color: #8da2b4;
  font-size: 12px;
}

.intro {
  position: fixed;
  inset: 0;
  background: radial-gradient(circle at top, rgba(23, 32, 44, 0.9), #0b0f13 65%);
  display: grid;
  place-items: center;
  z-index: 30;
  padding: 24px;
}

.intro-card {
  max-width: 1200px;
  text-align: center;
  background: rgba(16, 22, 28, 0.95);
  border: 1px solid #263140;
  border-radius: 16px;
  padding: 32px;
  box-shadow: 0 24px 60px rgba(0, 0, 0, 0.5);
}

.intro-kicker {
  margin: 0 0 8px;
  font-size: 18px;
  letter-spacing: 0.08em;
  text-transform: uppercase;
  color: #9cc9ff;
}

.intro-card h2 {
  margin: 0 0 16px;
  font-size: 32px;
  line-height: 1.2;
}

.intro-art {
  margin: 0 auto 20px;
}

.intro-art img {
  width: 100%;
  height: auto;
  display: block;
  border-radius: 12px;
  opacity: 0.85;
  mix-blend-mode: screen;
  filter: saturate(1.05) contrast(1.05);
  box-shadow: 0 18px 40px rgba(0, 0, 0, 0.45);
}

.intro-message {
  margin: 0 0 24px;
  font-size: 18px;
  color: #d4dbe5;
}

.intro-button {
  border: none;
  background: #2563eb;
  color: #f7fbff;
  font-size: 16px;
  font-weight: 600;
  padding: 12px 22px;
  border-radius: 999px;
  cursor: pointer;
  box-shadow: 0 10px 24px rgba(37, 99, 235, 0.35);
}

.intro-button:hover {
  background: #1d4ed8;
}

.intro-hidden {
  opacity: 0;
  pointer-events: none;
}

@media (max-width: 900px) {
  .flipbook {
    width: 100%;
    height: 100%;
  }
}

@media (prefers-reduced-motion: reduce) {
  .flipbook {
    transition: none;
  }
}