/* On board A: stable outer columns, two drifting inner grids. */
.onboard .ob-mask { clip-path:inset(-.25em); }
.onboard .ob-column-drift { display:grid;grid-template-columns:minmax(0,1fr);min-width:0;gap:inherit; }
.onboard .ob-photo-reveal { position:relative;overflow:hidden;isolation:isolate; }
.onboard .ob-curtain { position:absolute;inset:0;z-index:1;background:var(--ground);pointer-events:none; }
@media(prefers-reduced-motion:reduce) {
  .onboard .ob-mask { clip-path:none; }
  .onboard .ob-curtain { display:none; }
  .onboard .ob-column-drift { transform:none!important;opacity:1!important; }
}