.htaccess to remove index.php and subfolder from URL - .htaccess

Question

I am an .htaccess newbie and am having problems in removing a folder name from my sites URL.
It is currently: www.mydomain.com/engine
I have an expression engine site in a subfolder (named engine) of my hosts html folder. In this folder I have an htaccess document in which I have followed the directions in the expressionengine user guide to remove the index.php? from the URL succesfully, with:
RewriteEngine On
# Removes index.php from ExpressionEngine URLs
RewriteCond $1 !\.(gif|jpe?g|png)$ [NC]
RewriteCond %{REQUEST_FILENAME} !-f
RewriteCond %{REQUEST_FILENAME} !-d
RewriteRule ^(.*)$ index.php?/$1 [L]
I would now like to remove the "engine" referring to the subfolder from the URL too.
I have made numerous attempts going on advice in previous questions but have had no success.
On viewing www.mydomain.com, with any of my attempts I recieve:
Forbidden. You don't have permission to access / on this server.
I thought this could be a permissions problem, but this containing html folder has the same permissions as the "engine" folder which allows access.
Can anybody help with the .htaccess code i require?

Answer 1

yeh, the above rules don't apply to homepage url because it's a directory (doesn't pass the third RewriteCond), use the code below:
RewriteEngine On
# Removes index.php from ExpressionEngine URLs
RewriteCond $1 !\.(gif|jpe?g|png)$ [NC]
RewriteCond %{REQUEST_FILENAME} !-f
RewriteCond %{REQUEST_FILENAME} !-d [OR]
RewriteCond $1 ^$
RewriteRule ^(.*)$ /engine/index.php?/ [L]