Book about a robot building competition

[SevenB]

It was a book about teenage kids that built a robot for a competition or something of the sort, poor people lived below a ceiling, rich lived above, and at the end there was a war, or a big battle. I read it years ago, but it was so good, please help!

 

[tachyon]

Maybe The Inventors by Alexander Gordon Smith, my google search brought up this reddit post which looks similar

https://www.reddit.com/r/tipofmytongue/comments/b2a23b