Layer Toss

Seal both asymmetric shelves with one shared six-piece queue. Park one awkward piece on the floor, then use it later. A completed shelf counts only once. Switch shelf to plan both layouts. Park consumes an action and advances the queue, but does not discard the piece. Queue/floor chooses which piece to toss. Aiming, rotating, switching and rejected tosses are free. Undo returns pieces to their exact source, even across shelves. No timer.