I've played through the first 2 worlds of the game now, and it's really just been "Meh," the whole way through, as far as gameplay is concerned. There's not much challenge, but neither is there much fun. The best thing about the game is a sub-par combo system, so far. You spin into enough enemies with a short time between each hit, and are rewarded with relatively pointless jewels.
The game's cutscenes and non-gameplay art is gorgeous. Starfy, and all the characters in the game are drawn like soft, fluffy stuffed animals. So much so that every time I notice a "seam" drawn in, I can practically feel the fluffiness.
Aside from that, exploration is merely "Go in every direction, and look at the walls for a crack in them every once in a while." Starfy requires holding down a button to swim quickly, but it should have been automatic, as moving otherwise, is practically a crawl. On land, you hold the spin-button down to run, but you're not on land often, at least, not yet, so it's not too bad.
You gain abilities as you progress through the game, but not typically by any plot-driven means. Starly learned how to glide partway through the second world, and I was left wondering why they didn't just leave the glide available from the start, truly.
All-in-all, I feel like this game is almost exactly what it's marketed as: A beginner's platformer/exploration game, truthfully meant for children. There's not much gameplay, and the story is cute, at best, but has no where near the charm of say, a Pixar film, meant for all audiences. If you have a little brother or sister, or any child interested in gaming, The Legendary Starfy would be a great start, but I say this with respect when I say it's just not for us, ladies and gentleman.