Suspicious
good start, could use improvement
1) why is the navigation calendar-based? just make it a simple-to-scroll-through level system. there’s no need for it to be a calendar. as it is, it’s difficult to navigate, especially if you’re wanting to do multiple difficulty levels. it would make way more sense to just have three separate tabs for the three different difficulties, and then just back-to-back buttons for different puzzles (as an example, take a look at the level navigation of Flow Free, another puzzle game)
2) there should be a way to mark boxes that you know for sure won’t be filled with an X or dull gray shader. in the same vein, when you fill complete one part of a multi-number column or row (for example, a row that says “1 2”), it should fade out the number that’s been filled. (example: row requires a 1 and a 2. the 1 gets filled. the number 1 should become faded out to denote that it’s been correctly filled). this will make gameplay way smoother and less frustrating, especially at higher levels.
other than that, i really enjoy the overall design of this game. i feel it makes a good use of the screen space, which is something that a lot of picross-style games do not do very well.