Kagekaku

A science fiction juvenile fantasy set in a celestial city! Utopolis is a 7,000-meter-high skyscraper city. Zoe, a young girl born and raised in the city built inside a giant building, dreams of traveling to the "outside world. However, the residents of this city are obliged to "live in the building for the rest of their lives".

He is so annoyed by Bibi's inventions that he orders him to be grounded on the day of the Junior Science Contest as a punishment! What is Bibi's great invention of the century?