Is there a solution via htaccess?

Question

htaccess

Task: remove the folder address from the url
At the root of the site is a folder - folder, it in turn contains two files:
1) index.php
2) style file - style.css
Accordingly, index.php is available at site.com/folder /index.php Since the style file is on the same level as the index file,
it is included via a relative path -

<link rel="stylesheet" type="text/css" href="style.css" />

I need to remove the folder name from the url, that is, get the following from site.com/folder/index.php : site.com/index.php
When performing the following actions in htaccess, the page becomes available at a new address, BUT the style file stops connecting, now it
is connected along the path site.com/style.css (and of course it is not there, because it is in the folder folder)

RewriteEngine On

RewriteBase /

RewriteRule ^index.php$ folder/index.php [NC,L]

What needs to be added to htaccess so that the path to the css file does not change? I don’t want to just change the relative path to /folder/style.css, because the task is to hide the folder.

Answer 1

Try:RewriteBase /folder/

Answer 2

Didn't understand.
If you change the address of index, but do not change the address for css, then you still have to specify folder when connecting.