- * - Jigsaw Sudoku is currently an undocumented feature enabled
- * by setting r (`Rows of sub-blocks' in the GUI configurer) to
- * 1. The reason it's undocumented is because they're rather
- * erratic to generate, because gridgen tends to hang up for
- * ages. I think this is because some jigsaw block layouts
- * simply do not admit very many valid filled grids (and
- * perhaps some have none at all).
- * + To fix this, I think probably the solution is a change in
- * grid generation policy: gridgen needs to have less of an
- * all-or-nothing attitude and instead make only a limited
- * amount of effort to construct a filled grid before giving
- * up and trying a new layout. (Come to think of it, this
- * same change might also make 5x5 standard Sudoku more
- * practical to generate, if correctly tuned.)
- * + If I get this fixed, other work needed on jigsaw mode is:
- * * introduce a GUI config checkbox. game_configure()
- * ticks this box iff r==1; if it's ticked in a call to
- * custom_params(), we replace (c, r) with (c*r, 1).
- * * document it.
- *