/* =========================================
   新增：左上角返回鍵 (完全沿用 shop.css 風格)
========================================= */
.auth-fixed-back-btn {
  position: absolute;
  top: 30px;
  left: 30px;
  z-index: 100;
}

.back-btn {
  width: 40px;
  height: 40px;
  border-radius: 50%;
  background-color: #fff0f3;
  display: flex;
  justify-content: center;
  align-items: center;
  text-decoration: none;
  color: #ff6b81;
  font-size: 20px;
  font-weight: bold;
  transition: all 0.3s ease;
}

.back-btn:hover {
  background-color: #ffb7c5;
  color: white;
  border-radius: 15px 0 15px 0; 
  transform: scale(1.1) rotate(-5deg);
}