Need code review and want to understand my hack about height=0px

[nsisodiya]

My 50 lines of html/css code is available at - https://github.com/nsisodiya/layout/blob/main/src/App.js
and the above code is deployed at https://www.narendrasisodiya.com/layout/

Layout is working well as expected but I have few things to share.

• need code review.
• I have to use height 0px at one DOM element. Its my hack and I don't know how it is working. If I remove it, things break. is it a right way. what is alternate?
• I am not using calc and trying stuff using just pure css.
• is there any better way to do such simple layout.
• I have to use flex-grow flex all the time in entire DOM hierarchy. is this right way to use flex-grow so many times.

[garrettw]

Are you intending to submit a new flexbox bug + workaround that is not in the list?