// snippet from utility_helper.php
function asset_url()
{
    return base_url() . 'assets';
}

// snippet from autoload.php
$autoload['helper'] = array('url', 'utility');

Options +FollowSymLinks
RewriteEngine On
RewriteBase /app/main/build/www
RewriteRule ^$ index.php [L]
RewriteCond %{REQUEST_FILENAME} !-d
RewriteCond %{REQUEST_FILENAME} !-f
RewriteCond $1 !^(index.php|robots.txt|favicon.ico)
RewriteRule ^(.*)$ index.php?/$1 [L]