/* ============================================
   主题切换按钮
   ============================================ */

.theme-toggle {
  position: fixed;
  bottom: 20px; right: 20px;
  z-index: 999;
  width: 40px; height: 40px;
  border-radius: 50%;
  border: 2px solid var(--color-border);
  background: var(--color-surface);
  color: var(--color-text-secondary);
  cursor: pointer;
  font-size: 18px;
  display: flex;
  align-items: center;
  justify-content: center;
  transition: all 0.3s ease;
  box-shadow: var(--shadow-sm);
}
.theme-toggle:hover {
  border-color: var(--color-primary);
  color: var(--color-primary);
  box-shadow: 0 0 16px var(--color-primary-bg);
  transform: scale(1.1);
}
.theme-toggle:active {
  transform: scale(0.93);
}

/* 侧边栏遮罩（移动端） */
.sidebar-overlay { display: none; }