News homepage (SASS)

In the mobile view, when the side menu opens, the background becomes darker.

I obtained this effect with a ::after element that gets applied to the body when the menu button is pressed (and gave the side menu and the button a higher z-index). Is this the correct way of achieving the desired affect?

Also if i wanted to add a transition (ex. make the darker background fade in and fade out), how would i do that? Do i need another class and attach it to the ::after element or i can do it all throuh js or is there other ways? I tried but could not figure it out

Any other feedback is appreciated, thanks!