Matrix children inherited opacity

Community Usage questions
1

In a tab, which css is :

background:linear-gradient(to bottom,grey,black); 
opacity:.8;

i use a matrix of buttons. No background color for this one.
opac

Buttons have the same opacity, and i don't want that. I tried a few things, dealing with css, and var css... with no result...

How to have my buttons fully colored ?...

2

From https://www.w3schools.com/CSSref/css3_pr_opacity.asp

When using the opacity property to add transparency to the background of an element, all of its child elements become transparent as well. If you do not want to apply opacity to child elements, use RGBA color values instead