# Reflective symmetry (2 axes)

A polyomino has *reflective symmetry over both axes* if it is identical to its reflection over both the horizontal and vertical axes. A polyomino with this type of symmetry naturally has reflective symmetry over an axis. It also has two-fold rotational symmetry, since a 180˚ rotation is equivalent to flipping over one axis and then another. It is represented by the Klein four group.

The smallest polyomino that has this symmetry is the domino. Since the "straight" polyomino of every size is this symmetry (except for $n = 1$), this symmetry is represented in all sizes $n > 1$.