I literally completed the game in around a half-hour my first time playing it, on a school bus ride home. I didn't hold that against it, because the game was fun to play even if "simple." I think your review lingered on that point a bit longer than strictly necessary, but you brought up interesting trivia in the process and your construction and references to a much younger gamer did a good job of making your points. So I wouldn't necessarily change anything. Except, maybe, this sentence: "Kirby is one of the easiest and most fluid characters to control to grace the humble Gameboy." I feel like "to control to grace" feels a bit awkward there, even though it's not technically wrong. For that matter, nothing in your review seems technically wrong and it was all pleasant to read, so consider this one a job well done!
"Too often we enjoy the comfort of opinion without the discomfort of thought." - John F. Kennedy on reality
"What if everything you see is more than what you see--the person next to you is a warrior and the space that appears empty is a secret door to another world? What if something appears that shouldn't? You either dismiss it, or you accept that there is much more to the world than you think. Perhaps it really is a doorway, and if you choose to go inside, you'll find many unexpected things." - Shigeru Miyamoto on secret doors to another world
"What if everything you see is more than what you see--the person next to you is a warrior and the space that appears empty is a secret door to another world? What if something appears that shouldn't? You either dismiss it, or you accept that there is much more to the world than you think. Perhaps it really is a doorway, and if you choose to go inside, you'll find many unexpected things." - Shigeru Miyamoto on secret doors to another world
