I've played from March 11 all the way back to February 11. After 100%-clearing March with all three sets of stars and not getting a reward, I played only the advanced levels in February's set.
Comparing this game to Griddlers Plus (an android app that also continuously updates with new puzzles), and using my own sense of game design, here are a few notes I have:
* Add a dedicated "no" square. While I can "mark" cells, (and I use it quite extensively) it seems to be a "I think the square might be here" thing more than a "I think that a square is NOT here" thing. I say this because it's not visually obvious (like an X), so it can bleed into the background, making it harder to visually distinguished what's marked and what's not marked. Further, if I drag over it, a square fills it in anyway, which is not the desired effect. I expect it to skip over the marked cell for efficiency, not force me to restart cause I put a square in the wrong place.
* The penalty system needs to go. It makes the game too easy. What makes Griddlers Plus such an excellent implementation of Picross is that it's just like picross on-paper, i.e. you punish yourself and there's no omniscient referee telling you if you're right or wrong. If you screw up, you won't know until you're at the end and things aren't lining up, and you're forced to backtrack or restart. It forces you to be careful and logical without guessing. The penalty system here acts like a hint system. Why bother with hints when I can just guess a square and find out right then and there whether it's correct or not? What's to stop me from guessing and memorizing the screen? This is a case where traditional game idioms bite you in the ass, because the beauty of picross is in how one slip up can screw over your entire run. You shouldn't know precisely when that happens. It makes it too easy. That said, I've only made a couple mistakes. And by mistakes, I mean, accidentally clicking a square I knew I wasn't supposed to click because I didn't have enough information to determine if it was a yes or a no. Most of the time, it worked out for me...although I wouldn't know that had I done it in Griddlers--I would have seen that I marked the wrong square and hit undo.
* Along with the penalty system going away, you should start focusing on making "picture" levels in the spirit of picross. A picture that you worked for is much more rewarding IMO than three golden stars.
Perhaps the above two points could be its own game mode. "Classic"?
* An undo button would be nice. The play style I (and many other players) use involves extensive use of "no" squares to map out a column or row so I can quickly find the overlaps.
1 3 1 [ ][x][ ][!][!][ ][x][ ]
The x's are no marks, and the !'s represent the overlap of all the possible positions of the 3. At this point, it's convenient to hit undo twice and make the marks, or to make the marks and then erase the x's manually. Either way, an undo is nice for when you accidentally fill way too many squares and/or lost track of what you were doing.
* Have a finished column or row automatically get filled with x's ("no" marks) and optionally darken them. It makes it much easier to see what's going on so you don't misjudge distances.
* Keyboard controls. Like backspace or U for undo. R for restart. Q for quit. ? or H for hint. Assuming that's what the question mark in the corner does.
* Make the menu faster. It's a little annoying having to sit through the menu animations while I'm already ready to do the next puzzle. There should be a way to skip that, or to automatically jump to the next level on the same difficulty.
Overall, this is a pleasant game. A lot better already than most of the shitty picross games on the play store, and I'd even put it on par with professionally-made picross games like Mario Picross for the SNES. But Griddlers Plus still remains the best implementation available, in my opinion.