.theme-toggle-btn {
  position: fixed;
  top: 0.6rem;
  right: 0.6rem;
  z-index: 100;
  width: 2.4rem;
  height: 2.4rem;
  border-radius: 50%;
  border: 1px solid #d7dde3;
  background: #ffffff;
  color: #1f2933;
  font-size: 1.2rem;
  line-height: 1;
  cursor: pointer;
  display: flex;
  align-items: center;
  justify-content: center;
  box-shadow: 0 1px 4px rgba(0, 0, 0, 0.15);
  transition: background 0.2s, color 0.2s, border-color 0.2s;
  padding: 0;
}

.theme-toggle-btn:hover {
  opacity: 0.85;
}

:root[data-theme="dark"] .theme-toggle-btn {
  background: #1c1c20;
  color: #ececee;
  border-color: #2c2c31;
}