This was so interesting! I've never played Panel de Pon, though I did have a Puyo Puyo phase one or two years ago, which is similar in some aspects (not that many to be honest, but I want to believe it helped). The most difficult level for me was the tutorial, but it may have been simply because I didn't know the game; once I beat that, I finally understood how the game worked and really enjoyed it!
If I have to be honest, I didn't pay much attention to the "favourite object" mechanic because I already found it difficult enough to line up any kind of same-colour blocks, but I really appreciate how well thought-out the game is.
The story was quite fun too! I liked the humour, especially the part where Cirno got ignored (poor creature). The artstyle was nice; the board, in particular, looked just like out of a '90s puzzle game! You even took time and effort to add game modes other than the main story, which is something that shouldn't be taken for granted! Overall it's a very fun and challenging game, it really feels complete!