SOLVED. Middle Grade Fantasy book about a plane crash on an island that some kids survive. Spoilers ahead. [s]

[Anushka]

I can't remember any of the specific details of this book, but I know the general plot. A plane crashes onto an island and everyone on it goes unconscious (I think). A group of kids wake up on the crashed plane, and everybody else is missing. They all feel like something went through the plane and chose them, and they're worried that everyone is dead. On the island, they realize things that are red are safe, like red berries, and green things are dangerous, like some animal that attacks them is green. One of the kids climbs to a high point and falls and dies, but before that he says "Ur/Ear...". They think he was trying to say Earth, like he saw Earth, so they think they're on a different planet. However, later, another character sees the sky, sees a constellation, and realizes the boy that died was trying to say Ursa major/minor. They kids realize that this isn't a natural island, and that someone built it, after some event (can't remember).

[Rosa]

Horizon?

[Anushka]

Rosa wrote: "Horizon?"

Yes, it's this one. Thanks!

[Rosa]

Great, you're welcome.