The art is great, and you did a great job coming up with levels. Not only did you meet the challenge of fitting recognizable NG icons in 10x10 grids, but you did all 4 of them with the exact same number of filled-in tiles. Well done!
However, as a picross game this is definitely lacking. The controls are frustrating because it's awkward not being able to hold and drag to fill in multiple tiles at once, or to right-click to place an X. And it's too easy to cheat by using trial and error guesses. A solid picross game needs to solve that problem in one of two ways. There either needs to be a penalty for guessing incorrectly, or the game must never tell you that you have the correct answer until you've filled in the entire puzzle. Note that the game can still indicate that your row or column satisfies the requirements for that row or column, it would just do so without any promise that it's actually correct.
Also, I don't think there was any need to make the second medal a secret.