2.5 stars. The first 20 minutes or so are cute/funny. Then it goes off the rails. My kid is 11 and I felt fine watching with her, but I wouldn't recommend it for much younger than maybe 9 due to the talk of death, jokes about death, and other anxiety inducing topics and overall hard to follow story, which also includes time travel.
Also, it would get to an exciting part and then come to a halt due to the movie flashing to a Dad telling the story to his daughter and daughter interjecting with her own ideas and questions. Immersive, beautiful animation with a couple funny parts. But ultimately, the story is bonkers.
It's like the writer had some good ideas that could have been a 30 minute television episode, but needed 90 minutes so they kept adding in weird nonsense to get it to movie length. It had potential, but unfortunately did not reach it.