/* --- Base & Reset --- */
html, body {
  margin: 0;
  padding: 0;
  height: 100%;
  width: 100%;
  background-color: #050505;
  color: #ffffff;
  font-family: system-ui, -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, Helvetica, Arial, sans-serif;
  overflow: hidden; /* Prevent double scrollbars */
  -webkit-tap-highlight-color: transparent;
}

/* --- Fixed Header --- */
.top-bar {
  position: fixed;
  top: 0;
  left: 0;
  width: 100%;
  display: flex;
  justify-content: space-between;
  align-items: center;
  padding: 1.2rem 1.5rem;
  box-sizing: border-box;
  z-index: 100;
  pointer-events: none; /* Swipe through header space */
}

.logo {
  font-weight: 900;
  font-size: 1.3rem;
  text-transform: uppercase;
  letter-spacing: -0.5px;
  cursor: pointer;
  pointer-events: auto;
  text-shadow: 0 2px 10px rgba(0,0,0,1);
}

#menu-btn {
  background: none;
  border: none;
  cursor: pointer;
  display: flex;
  flex-direction: column;
  gap: 5px;
  pointer-events: auto;
  padding: 10px;
}

.hamburger-line {
  width: 25px;
  height: 3px;
  background-color: #ffffff;
  border-radius: 2px;
  box-shadow: 0 2px 5px rgba(0,0,0,0.8);
}

/* --- Scrolling Feed --- */
#app {
  height: 100vh;
  width: 100vw;
  overflow-y: scroll;
  scroll-snap-type: y mandatory;
  scroll-behavior: smooth;
  -ms-overflow-style: none;
  scrollbar-width: none;
}

#app::-webkit-scrollbar {
  display: none;
}

.feed-snap-item {
  height: 100vh;
  width: 100vw;
  scroll-snap-align: start;
  display: flex;
  justify-content: center;
  align-items: center;
  padding: 2rem;
  box-sizing: border-box;
}

.card-content {
  display: flex;
  flex-direction: column;
  align-items: center;
  width: 100%;
  max-width: 450px;
  height: 85vh;
  justify-content: center;
  text-align: center;
}

.genre-tag {
  text-transform: uppercase;
  font-size: 0.8rem;
  letter-spacing: 3px;
  color: #888;
  margin-bottom: 2rem;
  font-weight: 700;
}

/* Image Container with Intersection Observer Support */
.image-container {
  width: 100%;
  max-height: 60vh;
  aspect-ratio: 2/3;
  background-color: #111; /* Placeholder color */
  border-radius: 8px;
  overflow: hidden;
  box-shadow: 0 15px 50px rgba(0,0,0,1);
  margin-bottom: 2.5rem;
  position: relative;
}

.book-cover {
  width: 100%;
  height: 100%;
  object-fit: contain;
  opacity: 0;
  transition: opacity 0.5s ease;
}

.book-cover.loaded {
  opacity: 1;
}

/* --- Buttons --- */
.buy-btn {
  background-color: #ffffff;
  color: #000000;
  text-decoration: none;
  padding: 1.1rem 3.5rem;
  font-weight: 900;
  font-size: 1.1rem;
  border-radius: 100px;
  text-transform: uppercase;
  letter-spacing: 1px;
  transition: transform 0.1s ease, background-color 0.2s ease;
  width: 85%;
  max-width: 300px;
  box-shadow: 0 4px 15px rgba(255,255,255,0.1);
}

.buy-btn:active {
  transform: scale(0.96);
  background-color: #ddd;
}

/* --- Overlay Menu --- */
.menu-overlay {
  position: fixed;
  top: 0;
  left: 0;
  width: 100vw;
  height: 100vh;
  background-color: rgba(5, 5, 5, 0.98);
  backdrop-filter: blur(10px);
  z-index: 200;
  display: flex;
  justify-content: center;
  align-items: center;
  transition: opacity 0.3s ease, visibility 0.3s ease;
}

.menu-overlay.hidden {
  opacity: 0;
  visibility: hidden;
}

.menu-content {
  width: 100%;
  max-width: 400px;
  padding: 3rem;
  text-align: center;
}

.menu-title {
  font-size: 0.8rem;
  color: #555;
  text-transform: uppercase;
  letter-spacing: 4px;
  margin-bottom: 3rem;
}

#genre-list {
  list-style: none;
  padding: 0;
  margin: 0;
  display: flex;
  flex-direction: column;
  gap: 1.8rem;
}

.genre-link-btn {
  background: none;
  border: none;
  color: #ffffff;
  font-size: 1.8rem;
  font-weight: 800;
  text-transform: uppercase;
  cursor: pointer;
  padding: 5px 0;
  transition: color 0.2s ease;
}

.genre-link-btn:hover {
  color: #888;
}

.close-btn {
  margin-top: 4rem;
  background: none;
  border: 1px solid #333;
  color: #666;
  padding: 0.8rem 2rem;
  border-radius: 50px;
  cursor: pointer;
  text-transform: uppercase;
  font-size: 0.7rem;
  letter-spacing: 2px;
}

/* Desktop Optimizations */
@media (min-width: 768px) {
  .logo { font-size: 1.5rem; }
  .card-content { height: 90vh; }
  .buy-btn { width: auto; min-width: 250px; }
}

/* --- Modal --- */
#book-modal .modal-inner {
  background-color: #111;
  border-radius: 12px;
  position: relative;
  text-align: left;
  box-shadow: 0 10px 30px rgba(0,0,0,0.5);
  padding: 2.5rem;
}

#close-modal-btn {
  position: absolute;
  top: 15px;
  right: 20px;
  background: none;
  border: none;
  color: #888;
  font-size: 2rem;
  cursor: pointer;
  padding: 0;
  line-height: 1;
}

#close-modal-btn:hover {
  color: #fff;
}

#modal-title {
  margin-top: 0;
  margin-bottom: 0.5rem;
  font-size: 1.5rem;
  color: #fff;
  text-transform: none;
  letter-spacing: normal;
}

#modal-author {
  color: #888;
  margin-top: 0;
  margin-bottom: 1.5rem;
  font-size: 0.9rem;
}

#modal-desc {
  font-size: 1rem;
  line-height: 1.6;
  color: #ddd;
}