body, html {
  margin: 0;
  padding: 0;
  height: 100%;
}

.row {
  display: flex;
  align-items: center;      /* centra verticalmente el login */
  min-height: 100vh;        /* altura completa */
  margin: 0;
  background:     rgba(187, 74, 43, 0.8);
}

/* --- Columna con imagen de fondo --- */
.imagen {
  background: url('background.png') no-repeat center center;
  background-size: cover;
  flex: 1;
  min-height: 100vh;
}

/* --- Sección principal (formulario) --- */
.main-section {
  flex: 0 0 450px;          /* ancho fijo del bloque login */
  margin: 0 auto;
  padding: 0;
}

.modal-content {
  background-color: #3b4652;
  opacity: .9;
  padding: 20px;
  box-shadow: 0px 0px 3px #848484;
  border-radius: 22px;
  margin-top: 50px;
}

.user-img {
  margin-top: -80px;
  margin-bottom: 35px;
}

.user-img img {
  width: 140px;
  height: 140px;
  box-shadow: 0px 0px 3px #848484;
  border-radius: 50%;
}

/* --- Formularios --- */
.form-group input {
  height: 42px;
  font-size: 18px;
  border: 0;
  padding-left: 54px;
  border-radius: 5px;
}

.form-group::before {
  font-family: "Font Awesome 5 Free";
  position: absolute;
  left: 28px;
  font-size: 22px;
  padding-top: 4px;
  font-weight: 900;
  color: #555;
}

#user-group::before { content: "\f007"; }
#contrasena-group::before { content: "\f023"; }

button {
  width: 60%;
  margin: 10px auto 25px;
}

/* --- Responsive --- */
@media (max-width: 915px) {
  .imagen {
    display: none !important;
    background: none !important;
    height: 0 !important;
  }
  .row {
    display: block !important;
  }
  .main-section {
    flex: none;
    width: 100%;
    max-width: 400px;
    padding-top: 50px;
  }