/* 【修改点】背景容器与图片样式 */
#background-container {
  position: fixed;
  top: 0;
  left: 0;
  width: 100%;
  height: 100%;
  z-index: -1;
  overflow: hidden;
  background: #000;
}

.background {
  /* 共同样式：覆盖整个容器 */
  position: absolute;
  top: 0;
  left: 0;
  width: 100%;
  height: 100%;
  object-fit: cover; /* 保持比例，覆盖整个区域 */
  
  /* 初始状态：都透明且不可见 */
  opacity: 0;
  visibility: hidden;
  transition: opacity 0.5s ease; /* 淡入淡出效果 */
}

.background.active {
  /* 激活状态：显示 */
  opacity: 1;
  visibility: visible;
}

/* 原有样式保持不变 */
body { padding: 0; margin: 0; background: transparent; }
#unity-container { position: absolute }
#unity-container.unity-desktop { left: 50%; top: 50%; transform: translate(-50%, -50%) }
#unity-container.unity-mobile { position: fixed; width: 100%; height: 100% }
#unity-canvas { background: transparent }
.unity-mobile #unity-canvas { width: 100%; height: 100% }
#unity-loading-bar { position: absolute; left: 50%; top: 50%; transform: translate(-50%, -50%); display: none }
#unity-logo { width: 154px; height: 130px; background: url('TemplateData/unity-logo-dark.png') no-repeat center }
#unity-progress-bar-empty { width: 141px; height: 18px; margin-top: 10px; margin-left: 6.5px; background: url('TemplateData/progress-bar-empty-dark.png') no-repeat center }
#unity-progress-bar-full { width: 0%; height: 18px; margin-top: 10px; background: url('TemplateData/progress-bar-full-dark.png') no-repeat center }
#unity-footer { position: relative }
.unity-mobile #unity-footer { display: none }
#unity-webgl-logo { float:left; width: 204px; height: 38px; background: url('TemplateData/webgl-logo.png') no-repeat center }
#unity-build-title { float: right; margin-right: 10px; line-height: 38px; font-family: arial; font-size: 18px }
#unity-fullscreen-button { cursor:pointer; float: right; width: 38px; height: 38px; background: url('TemplateData/fullscreen-button.png') no-repeat center }
#unity-warning { position: absolute; left: 50%; top: 5%; transform: translate(-50%); background: white; padding: 10px; display: none }