Very cute, short game. For such a short game, there was a great sense of worldbuilding for not only the magic school, but how the world and the magic system worked at a fundamental level. It feels like something that can definitely be expanded on in the future. I liked the way you used the Picross to combine the spells together as things got bigger. Also cute subtle implication about the MC's identity in the epilogue if I'm not overthinking that.

Not too many issues with this, I think the biggest thing is that maybe the boards needed to be a little larger since the game tracks penalties so I was a little worried about misclicking at the 15 x 15 boards. Also I noticed that at times the game would say that certain parts of the lines or columns would be completed despite there still being doubt as to which of the options it could be. I've attached an example from my playthrough, where in the third and fourth row, the game filled in that both 1s had been completed despite there being a possibility for either of these ones to be in the 3rd column with the knowledge of the board I had at the time.

Overall these were just small issues all things considered, this game was great and cute and I loved it. I hope this maybe gets expanded upon in the future somehow.