How to make a global layout?

I'd like to make a single layout for all of my pages within the route structure, but I'm not quite sure how to do this.

If I make a

routes/(root).tsx

routes/(root).tsx

routes/(root).tsx

routes/(root).tsx file, then the

/

/ path shows up as that html & css, but nothing from

routes/index.tsx

routes/index.tsx

routes/index.tsx

routes/index.tsx populates the

<Outlet />

<Outlet />

<Outlet />

<Outlet />. And if I navigate to

/login

/login

/login

/login then the html & css from the layout doesn't appear at all.

So I'm not sure what it should be instead.