Most expanding galleries draw a second copy of the tile inside the overlay and fade between the two. That restarts whatever was in it, so a playing video jumps back to zero and an embed reloads. This moves the original layer instead, so state carries through. Only the transform animates, so nothing reflows mid travel. Tab reaches every tile, Enter opens, focus is held inside the panel while it is open and handed back to the tile on close, and Escape always closes even with Click Outside turned off. If the visitor asks for reduced motion the travel is skipped and the panel simply appears.