body, html {
  height: 100%;
  margin: 0;
  display: flex;
  justify-content: center;
  align-items: center;
}

body {
  background-color: #21252a;
}

.imagen-responsiva {
    width: 50%;
    height: auto;
    max-width: 100%;
}

@media (max-width: 600px) {
    .imagen-responsiva {
        width: 50%;
    }
}