:root { --sfondo: #fbfaf5; }
@media (prefers-color-scheme: dark) {
  :root { --sfondo: #111613; }
}
html, body { height: 100%; }
body {
  margin: 0;
  background: var(--sfondo);
}
main {
  min-height: 100%;
  display: grid;
  place-items: center;
  padding: 1.5rem;
  box-sizing: border-box;
}
h1 { margin: 0; line-height: 0; }
.logo {
  display: block;
  width: min(420px, 80vw, 80vh);
  height: auto;
  filter: drop-shadow(0 10px 24px rgba(0,0,0,.18));
}