/* Centered, intrinsic size on desktop; shrinks on small screens */
.img-fixed-center{
  display:flex;
  justify-content:center;
  align-items:center;
  width:100%;
}

/* Desktop/default: show at natural (intrinsic) size, no upscaling */
.img-fixed-center > img{
  display:block;
  width:auto;
  height:auto;
  max-width:none;     /* prevent theme rules from forcing 100% */
  max-height:none;
}

/* Small/mobile: allow it to shrink with the viewport */
@media (max-width: 640px){
  .img-fixed-center > img{
    max-width: 92vw;  /* shrink to fit */
    height:auto;
  }
}