A 4x4 grid has 3 shaded squares. Determine the minimum number of additional squares that need to be shaded to achieve rotational symmetry of order 2.

Here are the solutions to the questions. Question 6: To achieve rotational symmetry of order 2, if a square is shaded, the square diagonally opposite to it through the center of the grid must also be shaded. The original figure has 3 shaded squares. Let's assume the grid coordinates are (row, column) from (1,1) at the top-left to (4,4) at the bottom-right. The initially shaded squares are: (1,1) (1,2) (2,1) To make the figure rotationally symmetric of order 2, we need to shade the corresponding squares after a 180^ rotation. For $(1