Nonograms Katana. Sharpen your mind! You can play in a browser on PC and Mac, or download the app on Google Play and Apple App Store. Nonograms, also known as Hanjie, Griddlers, Picross, Japanese Crosswords, Japanese Puzzles, Pic-a-Pix, Paint by numbers and other names, are picture logic puzzles in which cells in a grid must be colored or left blank according to numbers at the side of the grid to reveal a hidden picture.