How to tie into one whole, regular tabs and side tabs?

Question

css

Hello.
It is necessary to make sure that the top and side tabs are connected, that is, if I select the top tab, then the selection goes to it, and if the side tab, then the selection goes from the top to the side. I hope the picture will be more clear :.

And on mobile devices, it folded like this:
.

Answer 1

by class active.
remove the bottom border from the top button peak, and make all the other 3 borders the same color as the table, and the same width.
It's the same with the side list, you remove the left border altogether, and you make all the rest the same as the table itself.