/* ================= BACK TO TOP ================= */
.back-to-top{
  position:fixed;
  right:32px;
  bottom:32px;
  width:48px;
  height:48px;
  border-radius:50%;

  background:#ffffff;
  color:#092D69;

  border:none;
  cursor:pointer;
  z-index:999;

  display:flex;
  align-items:center;
  justify-content:center;

  font-size:16px;

  /* estado inicial */
  opacity:0;
  pointer-events:none;
  transform:translateY(18px);

  /* glow suave cinza */
  box-shadow:
    0 6px 18px rgba(0,0,0,.12),
    0 0 0 1px rgba(0,0,0,.05);

  transition:
    opacity .4s ease,
    transform .4s cubic-bezier(.22,.61,.36,1),
    background .3s ease,
    color .3s ease,
    box-shadow .3s ease;
}

/* MOSTRAR */
.back-to-top.show{
  opacity:1;
  pointer-events:auto;
  transform:translateY(0);
}

/* HOVER – AZUL SUAVE */
.back-to-top:hover{
  background:#48C5F3;
  color:#092D69;

  box-shadow:
    0 10px 28px rgba(72,197,243,.35),
    0 0 0 1px rgba(72,197,243,.45);
}

/* MOBILE */
@media (max-width:600px){
  .back-to-top{
    right:18px;
    bottom:18px;
    width:44px;
    height:44px;
    font-size:15px;
  }
}