Color some of the white squares in each grid either red or blue. There is one red square and one blue square in each row and column. The colors of the squares outside some of the rows and columns are hints about where the largest consecutive string of white squares are. A red or blue hint square indicates this longest string is adjacent to that color square. A purple hint square indicates that this longest string is adjacent to both the red and blue square. A white hint square indicates there is more than one largest string. Below is a solved puzzle as an example. Each puzzle below has a unique solution. All puzzles copyright Erich Friedman, 2010.