/* 全屏动态渐变背景 */
html, body {
  margin: 0; padding: 0;
  height: 100%; overflow: hidden;
}
#bg {
  position: fixed; top: 0; left: 0;
  width: 100%; height: 100%;
  background: linear-gradient(-45deg, #1e3c72, #2a5298, #ff6e7f, #bfe9ff);
  background-size: 400% 400%;
  animation: gradientBG 15s ease infinite;
  z-index: -1;
}
@keyframes gradientBG {
  0% { background-position: 0% 50%; }
  50% { background-position: 100% 50%; }
  100% { background-position: 0% 50%; }
}

/* 通用面板样式 */
#login, #app {
  position: absolute;
  top: 50%; left: 50%;
  transform: translate(-50%, -50%);
  width: 320px;
  background: rgba(255, 255, 255, 0.8);
  border-radius: 12px;
  padding: 20px;
  box-shadow: 0 8px 20px rgba(0,0,0,0.2);
  text-align: center;
  font-family: 'Segoe UI', sans-serif;
}

/* 隐藏类 */
.hidden { display: none; }

/* 输入与按钮 */
input {
  width: 100%; padding: 10px;
  margin: 10px 0; border: 1px solid #ccc;
  border-radius: 6px; outline: none;
  font-size: 1rem;
}
input:focus {
  border-color: #2a5298;
  box-shadow: 0 0 8px rgba(42,82,152,0.5);
}
button {
  width: 100%; padding: 10px;
  margin-top: 10px; border: none;
  border-radius: 6px; background: #2a5298;
  color: #fff; font-size: 1rem;
  cursor: pointer; transition: opacity 0.2s;
}
button:hover {
  opacity: 0.9;
}

/* 标题与下载链接 */
h2 { margin: 0; font-size: 1.2rem; color: #333; }
h3 {
  margin: 15px 0 5px; font-size: 1rem;
  color: #444;
}
#cover-preview {
  width: 100%; border-radius: 6px;
  margin-bottom: 10px;
}
#download-links a {
  display: block; margin: 5px 0;
  color: #2a5298; text-decoration: none;
}
#download-links a:hover {
  text-decoration: underline;
}
#pwd-msg { color: red; margin-top: 5px; }