okayestjoel

Every 5x5 Nonogram was a collaborative, realtime web game released earlier this year with the ambitious goal to (collectively) solve all ~25 million line-solvable nonogram puzzles.

This is Part 2 in a behind-the-scenes look at some of the challenges in creating a public web game that anyone could play.

I think you're exactly right. I might be being a little loose with the terminology here. "Well-formed" may be a better term than "solvable" for what I consider a valid puzzle. Even if a computer program can find the solution to one of these difficult puzzles, it would be a very frustrating experience for a human player in most cases. For small 5x5 sizes you could get away with it, though imagine a larger 25x25 puzzle where you have to make one of these branching decisions (a guess) early on. Some may enjoy this challenge, though from my experience of running a nonogram game for 15 years I can tell you most will not.

I'm a little underwater handling the surge of traffic to my game, though when I get a quiet moment I'll run my solver so I can give some more precise answers. Basically my solver iterates over every row and column, marking cells that must be empty and painting cells that must be filled by going over every possible configuration for that row or column and finding the overlap. It does this in multiple passes and generally the more passes it takes, the more challenging the puzzle is. If it makes a pass and is unable to mark or paint any additional cells, then it considers the puzzle to be invalid if the end state is not solved (all clues are not satisfied).

I do find this discussion really interesting. Maybe I should have reserved "Section 666" for these puzzles with unique solution but require a branching strategy :).

In my mind, a well-formed nonogram is one that requires no backtracking. It's an interesting question though. I'll write some code in the next few days to check to see if my set of "unsolvable" puzzles include those with unique solutions given the clues.

Yeah, a "jump to unsolved" seems like its going to be essential. I'll work on that. I haven't heard of the scrolling issue. What device/browser are you using?

I believe none of the other 9 million have a unique solution. My nonogram solver goes over every possible configuration for each row and column based on the clues, and either fills in squares that must be filled (all possibilities overlap) or marks squares that must be empty. So if the solver reaches a point where there is ambiguity about what the next move is, then it is deemed not solvable (without guessing). A good example is a 5x5 puzzle where each row and column clue is "1": there are many possible 5x5 pixel grids that share those set of clues. Let me know if I'm misunderstanding your question.

This is my game! I was recently curious about how many 5x5 nonograms can be solved purely with logic, no guessing. After running my nonogram solver on all 33,554,432 possible pixel combinations in a 5x5 grid, it turns out the answer is 24,976,511.

Inspired by One Million Checkboxes, I thought it would be cool to create a realtime, collaborative nonogram game where we can collectively try to complete all ~25 million of these puzzles. Just launched it this afternoon and its already at 65k solved!

Let me know if you have any feedback.