/* Both boxes side-by-side via inline-block */
.expandable-box-A,
.expandable-box-B, 
.expandable-box-C, 
.expandable-box-D {
  vertical-align: top;        /* Align them at the top edge */
  
  /* Initial widths to share space (adjust as needed) */
  width: 100%;                 
  
  /* Smooth width transition */
  transition: width 0.3s ease;

  /* Some basic styling for clarity */
}