What is "shinro"

is a logic-based puzzle that has similarities to Sudoku and Minesweeper. The objective is to locate 12 hidden 'Holes' on an 8×8 grid. The board contains a variable number of arrows, each of which points to at least one Hole. A count of the number of Holes is given for each Row and Column.

Originally appearing in Japanese puzzle magazines, Shinro was popularized by its appearance in Southwest Airline's Spirit Magazine. It has since spawned web-based and iPhone versions.