I finally got this game.
I'm about at the end of the first half of the story mode (with some chests and golds still to do), and I already made 2 pages of challenges.
The game is good, but Canvas Curse was better, a lot better.
Just like I predicted in one of my old posts, the usage of clay is incredible, but the clay alone doesn't make the whole art style.
Keeping out the fact that everything is made out of clay, the art style feels generic, and even the music... lots of reused music from the past, and in some levels each room has a different music, like if the level doesn't have a main theme but a bunch of random themes.
Most of the remixes and the title screen theme are cool though, but there are also some boring and uninspired songs also (desert level -> generic desert music/beach level -> generic beach music), so much that in some parts it made me think of the New Super Mario Bros games.
The controls are fine, but in Canvas Curse the controls were a lot more precise. Now Kirby sticks a lot more on the rainbow rope compared to the prequel, and you can also stick him upside down; but I think this is a bit confusing, since it became harder to predict where Kirby is going, especially when there are multiple lines on the screen and you don't remember the direction you draw those lines (Kirby will most likely follow the original direction, unlike Canvas Curse where the rainbow line was just a platform and the direction was not changed by touching it - if I remember well).
Also, in Canvas Curse you was able to stun enemies, break blocks, activate switches, etc. with the touch screen, now you can only draw lines.
Anyway, it's still pretty fun.
I think that the challenges are the best part of the game (I thought the same of Returns to Dreamland), and, even if the gameplay feels a bit slow sometimes, the level design is well made (and it's pretty difficult at times).
The difficulty level is decent, and I have appreciated this; though I think that the difficulty curve is a bit unbalanced, and not very consistent: for example, first you have a couple of very easy levels, then, a very hard level with enemies that can one-shot you, then another easy level, and so; it's not a problem for me, but for some casual gamers it may be a problem.
Lastly, there is a big design flaw, that's the usage of the touch screen. This game was designed over the old DS, where the 2 screens had the same dimensions. On WiiU and 3DS, the main screen is the not-touch screen, and a game like this, that's mainly played on the touch screen, doesn't make much sense on Nintendo's current gen consoles. None of the 2 consoles were suited for this game, but of the two consoles, they choose the worst one, the least suited; it should have been a 3DS game to me.
The game has a very big Mass Attack feel, and just like Mass Attack, I like it but it's still not one of my personal favorites.
Don't get me wrong, I like it very much, I love the characters and it's fun, it's definitely a good game, it's just that a game like Triple Deluxe feels a lot better in comparison, and the whole concept of Kirby rolling on rainbow lines is rehashed from a previous game, while usually Kirby's spin-off titles are original.
Overall score: 8 (I gave 10 to Triple Deluxe).
The score may change when I'll 100% the game, but I doubt, as I already spoiled myself the whole game months ago and I already know its content.