Hooked on Picross

Posted in Games

I just discovered Picross.

Also known as nonograms, they’re these puzzles that involve filling out 2D—and sometimes, 3D—grids. Clues to which areas are to be filled are listed down the sides of the 2D/3D grid area, and gameplay is all about making logical inductions to paint in squares/cubes as either filled in or empty. Upon completion, the reward is seeing the picture or model.

From a gameplay standpoint, the game is reminiscent of Sudoku in that it’s mostly about logical reasoning. It turns out that both puzzle types also share an added quality with grids and numbers, but so far I’ve been finding the puzzle solving in Picross to be more satisfying. Some of it can be attributed to the reward of seeing a pixelated painting at the end of a play session; a part of the fun is simply guessing the depicted drawing/sculpture as the puzzle gets filled out. The rest, though, I suspect is due to how to infer solutions to Picross puzzles.

Sudoku is a solved problem (PDF). There are known algorithms to generate sudoku puzzles of all levels of difficulties, and all the ways to infer values on the grid are understood and accounted for in that difficulty. The attraction of sudoku comes from applying that mechanical process, which can look magical and complicated to the unwitting observer but rote to the seasoned practitioner. It reminds me a little of learning how to solve a Rubik’s cube.

With Picross, a major part of my joy is having to discover my own rules for solving its puzzles1. They become necessary as the boards get bigger and the clues get fewer, but Picross’s rules seem more approachable, easier to deduct ex nihilo given enough time and mental effort. There’s also beauty of coming up with complex inferences from very simple rules, and that these rules are both applicable across the entire board (e.g., filling out a full column/row) as well as in small, enclosed areas.

These properties echo that of Go, another game that’s praised for its simplistic beauty but overwhelmingly deep strategy. Of course, Picross only captures a tiny portion of that complexity2.

Anyway, if all of this sounds intriguing, I found a really good iOS/Android/PC game that’s free to start, and is well worth the in-app purchase if you get hooked onto the game like I did: Paint it Back. Happy puzzling!

  1. And to not rob that sense of discovery for the reader, I’m going to resist linking to any nonogram strategies here.

  2. Interestingly, in doing research for this blog post, I learned that nonogram solving is a NP-complete problem, which may explains why I’m attracted to them.