Highlights in Big Bad Sudoku Book are a revolutionary way to see and solve sudoku puzzles. With highlights you can softly highlight cells, rows, or columns with the swipe of a finger. They help focus your attention and narrow down possibilities. You can use highlights to temporarily mark positives or negatives, but more often they can be used to keep track of where an answer can’t go.

Here’s an example from actual game play. In each of these following screen shots the red drawing is not part of the game but has been added to explain how the Big Bad Sudoku Book works. Click on the pictures to see them bigger:

In this sample game let’s start by trying to figure out where some of the 7’s go. By tapping and holding on any one of the 7’s all 7’s are highlighted:

Since there is a 7 in that top row there can’t be any more 7’s in that row.  Touching outside of the first row and swiping into the row (action shown in red) highlights the whole row:

There’s also a 7 in the second row (underlined in red). Swiping into that second row highlights it as well:

Next we can see that there’s a 7 in the second column. Swiping down into that column highlight it. Now we can see that in that first block the only remaining place where a 7 can go is in the cell that’s been circled in red. This is the power of highlighting. When used in this way it doesn’t just give you the answer, but helps focus your attention to find the answer:

Taking it a step further, after placing a 7 in that cell you could swipe down that column and highlight it to reveal where another 7 goes. But the Big Bad Sudoku Book has another trick that does it all at once. For this simple puzzle it really gives us too much help, but it’s a feature that you can use when you need it. As shown in that first screenshot, by tapping and holding on the 7 it highlights all instances of the 7. If you tap and hold again on the 7 it will highlight every row, column, and block that those 7’s are in:

This means that all of these highlighted cells can not be 7’s because there can’t be more than one instance of any number in any row column or block. From this you can easily find what cells are left to hold 7’s – the ones not highlighted. After filling in the 7 in that first block (shown here in red), it also eliminates that first column and points to the location of the next 7.  Continuing this narrows the search down even further. Of course using highlights is completely optional – but it’s there when you need it.

To clear all highlights tap anywhere outside of the puzzle area.