/* (PART A) HTML IMAGE */
#demoA1 {
  /* (A1) 100% WIDTH */
  width: 100%;

  /* (A2) OPTIONAL RESTRICTIONS */
  aspect-ratio: 16/8;
  object-fit: cover;
  max-width: 600px;
}

/* (PART X) COSMETICS - NOT REALLY IMPORTANT */
* {
  box-sizing: border-box;
  font-family: Arial, Helvetica, sans-serif;  
}