13. (15 points) Eight $2 \times 1$ small rectangles as shown in the figure can be used to form a $4 \times 4$ square. If a square formed by these rectangles is the same as another square after rotation, they are considered the same square. How many different squares can be formed where both diagonals are axes of symmetry?
【Analysis】Use the right figure
to replace the $2 \times 1$ rectangle in the problem, because the given small rectangle is asymmetrical up and down, so in the square figure formed by the small rectangles where both diagonals are its axes of symmetry, this way, we only need to consider different scenarios in the upper half, and analyze and solve the problem accordingly.

【Solution】Solution: As shown in the figure:
Answer: 4 types of square figures can be formed where both diagonals are axes of symmetry.
