body {
  background-image: url("https://www.exa.unrc.edu.ar/wp-content/uploads/2019/02/quimica.jpg");
  background-size: cover;
  background-position: center center;
  background-attachment: fixed;
  height: 100%;
}

.login-heading {
  font-weight: 300;
}

.btn-login {
  font-size: 0.9rem;
  letter-spacing: 0.05rem;
  padding: 0.75rem 1rem;
}
#estilo {
  background-color: rgba(0, 0, 0, 0.5);
}