I see! Lucky that my latest Hard Puzzle had London in it!
Unfortunately, the pure black and white is causing a small amount of https://en.wikipedia.org/wiki/Grid_illusion
And there was more contrast when grids were colored differently than the background, but I can adjust. Thanks for the update!
EDIT: Would be nice if the game checks for solutions like "if you've completed 4 of the right grids, you've completed the whole puzzle. Like if in Hard mode, you complete the top set of 4 grids, there's no new info to find.
EDIT 4: But it seems if I complete some bigger subset, it also fully completes. I can't quite tell / remember.
EDIT 2: A clue set in Hard 73336:
1. A may be Y or Z
2. A is not Z
can happen, which seems silly and should just be merged into "A is Y"?
EDIT 3: Same Puzzle as ^, might not want "Year of the Horse" and "horse as a pet" both as options.