* {
  box-sizing: border-box;
}

body {
  font-family: sans-serif;
  margin: 0;
  padding: 0;
  display: flex;
  flex-direction: column;
  min-height: 100vh;
}

header, footer {
  background: #333;
  color: #fff;
  padding: 1rem;
  text-align: center;
}

main {
  flex: 1;
  padding: 2rem;
}

form {
  margin-bottom: 2rem;
}

input[type="file"] {
  margin-right: 1rem;
}

button {
  padding: 0.5rem 1rem;
  border: none;
  background: #007bff;
  color: #fff;
  border-radius: 4px;
  cursor: pointer;
}

button:disabled {
  background: #aaa;
  cursor: not-allowed;
}

#chapters button {
  display: block;
  margin: 0.5rem 0;
  width: 100%;
}

/* Modal backdrop */
.modal {
  display: none;
  position: fixed;
  z-index: 1000;
  left: 0;
  top: 0;
  width: 100%;
  height: 100%;
  overflow: auto;
  background: rgba(0,0,0,0.6);
}

/* Modal content box */
.modal-content {
  background: #fff;
  margin: 5% auto;
  padding: 1rem;
  border-radius: 8px;
  width: 90%;
  max-width: 600px;
  position: relative;
}

/* Close button */
.close {
  position: absolute;
  right: 1rem;
  top: 1rem;
  font-size: 1.5rem;
  cursor: pointer;
}

/* Chapter body scrolling */
.modal-body {
  max-height: 60vh;
  overflow-y: auto;
  margin: 1rem 0;
}

/* Download button */
.download-btn {
  display: block;
  margin: 0 auto;
  padding: 0.5rem 1rem;
  border: none;
  background: #28a745;
  color: #fff;
  border-radius: 4px;
  cursor: pointer;
}