SOLVED. Juvenile fiction about a boy who made made things out of cardboard but they actually worked. [s]

[Help]

Read 2-7 years ago from a local library, have since moved so can no longer check there. Most likely a hardback book, but could have been paperback.

one thing from it was that he made a sword that "cut things in half on a subatomic level" or something, and after cutting a fishbowl in half the fish was still able to swim back and forth between the sides without the sides being connected. If I recall right, he had cut the fishbowl on the backstroke of a swing to try cutting something else. I feel like there was something about the sword blade being made from a magnetic field or something?

I think at some point there may have been a vehicle constructed?

I remember that he had like a younger brother or something and at one point he gave the younger brother some of his cardboard.

most likely main character was in elementary school, possibly middle school.

[Julia]

Cardboard by Doug TenNapel?

The Cardboard Kingdom by Chad Sell?

[Help]

Julia wrote: "Cardboard by Doug TenNapel?

The Cardboard Kingdom by Chad Sell?"

No, it would definitely be a book and not a graphic novel, and the things he made out of cardboard canonically worked in the story as opposed to being a game of make-believe

[Ayshe]

Gravity Buster: Journal #2 of a Cardboard Genius? I noticed it suggested on another website and it seems to match.

[Help]

Ayshe wrote: "Journal of a Cardboard Genius? I noticed it suggested on another website and it seems to match."

I think that's it, thanks!