.grid-container {
  display: grid;
  grid-template-columns: repeat(1, 1fr);
  grid-auto-rows: auto;
  gap: 1rem;
}

@media (min-width: 900px) {
  .grid-container {
    grid-template-columns: repeat(6, 1fr);
    gap: 2rem;
  }

  .span-3x1 {
    grid-column: span 3;
    grid-row: span 1;
  }

  .span-3x2 {
    grid-column: span 3;
    grid-row: span 2;
  }

  .span-3x3 {
    grid-column: span 3;
    grid-row: span 3;
  }

  .span-6x1 {
    grid-column: span 6;
    grid-row: span 1;
  }
}