/* PC/SP共通：flexで中央揃え */
#customer_header{
  display: flex !important;
  justify-content: center !important;
  align-items: center !important;
  text-align: center !important;
}
#customer_header .logo{
  display: inline-block !important;
  margin: 0 auto !important;
  float: none !important;
}

/* PCサイズ固定 */
#customer_header .logo img{
  height: 43px !important;   /* PC用高さ */
  width: auto !important;
  max-height: none !important; /* max-heightの影響を防ぐ */
}

/* スマホ（640px以下）だけサイズ変更 */
@media (max-width: 640px){
  #customer_header .logo img{
    height: 40px !important;  /* SP用高さ */
  }
}