/* ============================================================
   背景切换弹板 · 仿 Element Plus Dialog 风格
   清树工具站
   ============================================================ */

/* 遮罩层 */
.bg-overlay {
  position: fixed;
  top: 0; left: 0; right: 0; bottom: 0;
  z-index: 2000;
  background: rgba(0, 0, 0, .5);
  display: flex;
  align-items: center;
  justify-content: center;
  opacity: 0;
  visibility: hidden;
  transition: opacity .25s ease, visibility .25s ease;
}
.bg-overlay.show {
  opacity: 1;
  visibility: visible;
}

/* 弹板容器 */
.bg-dialog {
  width: 480px;
  max-width: calc(100vw - 40px);
  max-height: calc(100vh - 80px);
  background: #fff;
  border-radius: 12px;
  box-shadow: 0 12px 48px rgba(0, 0, 0, .2);
  overflow: hidden;
  transform: scale(.92) translateY(10px);
  transition: transform .25s cubic-bezier(.34,1.56,.64,1);
  display: flex;
  flex-direction: column;
}
.bg-overlay.show .bg-dialog {
  transform: scale(1) translateY(0);
}

/* 弹板头部 */
.bg-dialog-header {
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding: 18px 22px 14px;
  border-bottom: 1px solid #f0f0f0;
}
.bg-dialog-title {
  font-size: 16px;
  font-weight: 600;
  color: #1f2937;
}
.bg-dialog-close {
  width: 28px; height: 28px;
  border: none;
  background: none;
  cursor: pointer;
  border-radius: 6px;
  display: flex;
  align-items: center;
  justify-content: center;
  color: #9ca3af;
  font-size: 18px;
  transition: background .15s, color .15s;
}
.bg-dialog-close:hover {
  background: #f3f4f6;
  color: #374151;
}

/* 弹板内容区 */
.bg-dialog-body {
  padding: 18px 22px 22px;
  overflow-y: auto;
  flex: 1;
}

/* 分组标签 */
.bg-group-label {
  font-size: 13px;
  font-weight: 600;
  color: #6b7280;
  margin-bottom: 10px;
  letter-spacing: .5px;
}
.bg-group {
  margin-bottom: 20px;
}
.bg-group:last-child {
  margin-bottom: 0;
}

/* 颜色/渐变 网格 */
.bg-color-grid,
.bg-gradient-grid {
  display: grid;
  grid-template-columns: repeat(6, 1fr);
  gap: 10px;
}
.bg-color-item,
.bg-gradient-item {
  width: 100%;
  aspect-ratio: 1 / 1;
  border-radius: 8px;
  cursor: pointer;
  border: 2px solid transparent;
  transition: transform .15s, box-shadow .15s, border-color .15s;
  position: relative;
  overflow: hidden;
}
.bg-color-item:hover,
.bg-gradient-item:hover {
  transform: scale(1.08);
  box-shadow: 0 4px 14px rgba(0, 0, 0, .15);
}
.bg-color-item.active,
.bg-gradient-item.active {
  border-color: #49b1f5;
  box-shadow: 0 0 0 3px rgba(73, 177, 245, .25);
}

/* 图片网格 */
.bg-image-grid {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: 10px;
}
.bg-image-item {
  aspect-ratio: 16 / 10;
  border-radius: 8px;
  cursor: pointer;
  overflow: hidden;
  border: 2px solid transparent;
  transition: transform .15s, box-shadow .15s, border-color .15s;
  background: #f3f4f6;
}
.bg-image-item img {
  width: 100%;
  height: 100%;
  object-fit: cover;
  display: block;
}
.bg-image-item:hover {
  transform: scale(1.03);
  box-shadow: 0 4px 14px rgba(0, 0, 0, .15);
}
.bg-image-item.active {
  border-color: #49b1f5;
  box-shadow: 0 0 0 3px rgba(73, 177, 245, .25);
}

/* 响应式 */
@media (max-width: 520px) {
  .bg-color-grid,
  .bg-gradient-grid {
    grid-template-columns: repeat(4, 1fr);
  }
  .bg-image-grid {
    grid-template-columns: repeat(2, 1fr);
  }
  .bg-dialog {
    width: calc(100vw - 24px);
  }
}