I'm confused by this part of the pre-ramble:
"All the letters of the symbol appear in a central region of the completed grid (with 90° rotational symmetry and occupying 64 cells)."
Is it the "
central region" that has 90 degree symmetry and occupies 64 cells, or the
letters of the symbol? If it's the central region, then, given the bars in the grid, there seems to be only one possibility for the "region". So I feel like I'm missing something.