body {
  font-family: Arial, sans-serif;
  margin: 0;
  background: #f5f5f5;
  color: #333;
}

header {
  background: #222;
  color: #fff;
  padding: 1rem;
  display: flex;
  align-items: center;
  justify-content: space-between;
}

header a, header button {
  color: #fff;
  text-decoration: none;
  background: #444;
  border: none;
  padding: 0.5rem 1rem;
  cursor: pointer;
}

main {
  padding: 1rem;
}

/* Library */
.manga-card {
  display: inline-block;
  margin: 1rem;
  text-align: center;
  cursor: pointer;
}
.manga-card img {
  width: 150px;
  height: 220px;
  object-fit: cover;
  border-radius: 5px;
}

/* Chapters */
.chapter-card {
  display: inline-block;
  margin: 1rem;
  text-align: center;
  cursor: pointer;
}
.chapter-card img {
  width: 120px;
  height: 180px;
  object-fit: cover;
  border-radius: 5px;
}

/* Viewer */
#viewer {
  text-align: center;
}
#viewer img {
  max-width: 45%;
  margin: 0.5rem;
  vertical-align: middle;
  border-radius: 5px;
}

.nav-btn {
  position: fixed;
  top: 50%;
  transform: translateY(-50%);
  background: rgba(0,0,0,0.6);
  color: white;
  border: none;
  padding: 1rem;
  cursor: pointer;
  font-size: 1.2rem;
  border-radius: 5px;
}
#prev-btn { left: 10px; }
#next-btn { right: 10px; }