Here is a list of the pieces I have already collected.

Piece 1 [x]
Piece 2 [x]
Piece 3 [x]
Piece 4 [x]
Piece 5 [x]
Piece 6 [x]
Piece 7 [x]
Piece 8 [x]
Piece 9 [x]
Piece 10 [x]
Piece 11 [ ]
Piece 12 [x]
Piece 13 [x]
Piece 14 [x]
Piece 15 [ ]
Piece 16 [x]

No more extras to swap

11 and 15 to go