(defvar *combinations*
  (loop for p0 below 4
        append (loop for p1 below 4
                     append (loop for p2 below 4
                                  append (loop for p3 below 4
                                               when (= (length (remove-duplicates (list p0 p1 p2 p3))) 4)
                                               collect (list p0 p1 p2 p3)))))
  "A list of all the combinations to try -- consisting of lists of chunk positions.")

((0 1 2 3) (0 1 3 2) (0 2 1 3) (0 2 3 1) (0 3 1 2) (0 3 2 1) (1 0 2 3)
 (1 0 3 2) (1 2 0 3) (1 2 3 0) (1 3 0 2) (1 3 2 0) (2 0 1 3) (2 0 3 1)
 (2 1 0 3) (2 1 3 0) (2 3 0 1) (2 3 1 0) (3 0 1 2) (3 0 2 1) (3 1 0 2)
 (3 1 2 0) (3 2 0 1) (3 2 1 0))