3 ms·

Oh, right. But what about the ones on row 1?

• sp332 12y ago
  Well if you switch the squares on row 3, you have to switch the square on row 1 as well. Otherwise the columns will not have even numbers of red and blue squares.
  • anon4 12y ago
    Oh. It's really confusing to show not only the current mistake but also the mistakes that would be introduced by fixing it.
    • sp332 12y ago
      True. There is only a single solution to each puzzle, so it just highlights all the blocks which don't match the known solution.
• deleted 12y ago
  [deleted]