Hello, I made a small demo for a Hanjie/Nonogram/Griddler game. It comes with a few dozen puzzles but you can draw your own. It‘s meant as a coffee table game where you casually draw and solve puzzles between multiple people.
One gotcha: to save a puzzle you have to solve it yourself once. This is the cheapest way to assure that the puzzle is solvable before handing it over to your friends.
EDIT: finished game at Sketch, Share, Solve by RDK
Ah! Excellent! 
I always thought that the playdate would be the perfect console for a Picross game with it's super contrasty and easy to read screen.
Are you looking for feedback?
Yes, that would be great. There‘s still a lot of room for improvement. 
So I finally spend some times with the game.
As expected I really enjoyed solving these puzzle on the playdate, I think this is a great match.
Highlighted cell with inverted color works well enough but I had few times when I was not sure what was selected or the actually state of the cell. The problem is mainly when you switch between empty and filled because empty selected is all black so it intuitively feel like the cell is set.
It is rather a small problem that the player will get used to but it is also the type of problem that are fun to polish.
My suggestion would be to have a cursor instead of inverting the cell color. A cursor tends to also to be easier to find in a screen adding a bit of extra ease of use.
It can be a bit difficult to find the number corresponding to the current row and column. I would highlight the row and column to know what number are important. You can do that just by showing the guideline for the current row/column.
I really like how you handle the cursor movement. The repeat speed is good. I like that holding the button only the set empty cell and not overwrite cells that are already set. The cursor looping the board is also a nice touch. Maybe I would recommend to try to not have the cursor looping the board when the player hold a button though because usually they just want to fill until the end of the line. But that's a small details.
The typeface for the number is not super readable in this context. The size is fine but they all use very straight line and the same sharp angles so at a glimpse they are too similar. There is a lot of numbers on screen and having a font that makes it easier to differentiate between them would be a big help.
I am not a big fan of navigating the menu with the crank. I really like the idea that you open the menu with the crank because it helps the user create a good distinction between the game and the menu but in practice I found that it was rather counterintuitive and I always wanted to use the D-Pad. When you finish a puzzle there is no indication you should undock the crank to open the menu, I think that would be a helpful reminder.
Revealing the image when you finish the puzzle was a bit too sudden and unceremonious. This is more a polish task and I am sure you plan to add more polish and juice down the line but that the thing that was really missing for me. That would be cool also to celebrate the small victories like when a line or column is done and correct (a small audio feedback or checkmark would be enough)
Out of curiosity, do you use playdate.stop() ?
I am quite intrigued by the idea of doing a power efficient game that would update and render only on player inputs. This game would be a good candidate for that.
What is your plan for sharing puzzle between users? That might be an overkill at this point but it would be awesome to use some server to host the puzzles and to save a puzzle you would just have to scan a QR Code. That would mean the game would need to access the server and the SDK doesn't support that yet. But that would be cool.
I hope it's not too much feedback and that it can be useful. 
Thanks a lot for your feedback. I‘ve implemented most of your suggestions in the latest build. The winning animation will have to wait a bit longer as I haven‘t had the right idea for it yet.
Out of curiosity, do you use
playdate.stop()?
I‘ll try playdate.stop() at some point but first I‘ll have to figure out how to not break my animations which are currently tied to playdate.update.
What is your plan for sharing puzzle between users?
I don‘t think I‘d ever run a server for sharing but if Playdates could exchange puzzle directly via wifi or bluethooth that would be amazing.
I miss marks near the numbers that the vertical line or horizontal line is complete and you can ignore it.
I think animation when you press A or B on the cell (mark appear animation) shoul be faster.
It took me a while to understand that you need to dock crank to hide menu 
I've solved 3/14 pazzles is one go, great game! 
The idea of player profiles is SUPER great!
Selection of creator made me want to collaborate and add my puzzles.
I hope you will add differend puzzle sizes and sectional puzzles (you need to solve 4 15x10 puzzles to see one 30x20 picture) 
Thanks a lot for your feedback.
@Whitebrim This is interesting. Did you play with hints (where numbers are bold if the corresponding block hasn’t been placed) and would like an additional mark for the column/row or did you play without hints?
I’d love to but not sure I’ll ever find the time. Solving sectional puzzles would be straightforward to implement but I’m not sure I could fit the authoring tools needed to create them without frustrating players (due to both the tiny screen and the limited processing power).
I realised that I've turned off hints, so what they were, thank you
I’ve uploaded a feature complete version with 99 levels. Have fun.
Nonogram is great. This is great and you are great! Thank you for making this
Wow! I've been working on my own Picross/Nonogram game as a way to learn Lua, and have just got in running on the Playdate Simulator. It's nowhere near as nice as yours, but it was a fun first attempt from a complete beginner!
Picross.pdx.zip (32.5 KB)
I love the vibe! You have no idea how nice it is to see a different design after looking at your own for months. 
Well yours is beautiful and certainly inspirational to me!
i Really like your game. if i make 100 levels may i post it here?
Sure. You should also consider posting a comment on the game’s page as that will have more visibility long-term.