Triple Tango

Designed by Jerry Loo, made by Eric Fuller, 2016.
(Maple, Mahogany, Walnut, Acrylic, 6" x 3.75" x 3/4";
removable acrylic cover has starting position etched on it)

Exchange pieces A and B and finish with the other pieces in their original positions. Below are selected steps, including every step in which piece X moves, of a solution of 33 rectilinear steps (53 straight-line steps, 74 unit steps). Note that at step 22 pieces A and B are exchanged, and the remaining steps put the other pieces back.