Mirror axis

Many symmetry groups have a mirror or glide symmetry axis (or both). You must tell Context Free which axis is the mirror or glide axis by providing an axis specification, which is an integer from 0 to 3. This image shows the number for the four possible axes: x, y, x=y, and x=-y. The x=y and x=-y axes are only used for the 45° rotated square tiling grids.