The wall
Watch several live channels and films at once. Nothing plays until you press Start. Sound comes from one tile, the one you choose; each tile fetches only the picture its size needs, and the tiles you are not watching take the smallest picture that is still watchable.
One press starts every tile. Arrow keys move between tiles, and the sound goes with you unless you keep it on one tile; Enter makes a tile big; Shift with an arrow moves a tile, Alt with Shift and an arrow resizes it; M mutes all.
Nothing on the wall yet. Add a tile: what is on now comes first.