Well the difference between rotational symmetry and x y xy symmetry, is that rotational symmetry creates 4 identical "pieces of pie", whereas x y xy symmetry creates 4 pieces of a square that all mirror each other over both the x and y plane.

To try to give you a visual: in order to create a map with rotational symmetry, the only mirrors are the top left and bottom right sets, all directly tangent corners of the map are not necessarily mirrored. So this means that you create a single piece of your map: a single corner. This corner can be the bottom left, bottom right, top left, or top right. From here you construct the other three identical sides, but they aren't mirrored to the first; they are rotated either clockwise or counter clockwise from the first piece.

Take a look at this image:



This image isn't mirrored over a line of symmetry, however, you can draw a line from the top left to the bottom right and cut this image in half. After that, you can rotate one piece onto the other, and they will be identical.

X Y XY made maps have all four corners mirror each other, while rotational symmetry uses identical (but rotated) patterns.

Note: If the map is two player, you can use rotational symmetry with only 2 "pieces of pie", but if you have four players then you would want 4 identical pieces. The above picture only has 2 "pieces of pie", but it gets the point across of what rotational symmetry is.

Here is a better example of rotational symmetry:



You can see that this picture has no mirrors (unlike the galaxy), but still has rotational symmetry; each third of the picture is identical, and is just rotated 120 degrees from the last third. This is what you would be doing with your map, just with fourths instead of thirds.

So like I said, the only identical parts of a 4 player map with rotational symmetry, would be the diagonal mirrors. You can take advantage of this, and use the xy button to create 2 sides of your map at once.

this may sound crazy, bear with me i have just recently started map making, but is it possible to do a symmetrical flip on a diagonal line for example having the top left vs the bottom right?