Ah, what a nice game ;_;
I was really happy about how compassionately both Cassia and Senna are treated... having read Starry Flowers, it's nice to know Cassia finds happiness..! I hope Senna does, too - she struck me as the "gifted kid burnout" type, so I got really worried by the last day! (And the epilogue!)
The puzzles are really fun, too! To think that this is all renpy... that's amazing... The patterns are cute, and the difficulty curve is really gentle. I was really happy to see more of them in the gallery afterwards!
I skipped the tutorial, so I can't speak to that, but even without the verbal explanation ahead of time, it's easy to find a nice starting point in the early ones, and it felt like some of the intermediate concepts are just kind of naturally taught through the puzzles themselves..? And then it really ramps up for the bonus ones! Oh, and I liked the short thoughts in the music gallery, too... so much charm in such a short VN!