RewriteEngine On

# Allow actual physical files and folders to load normally (like CSS, JS, images)
RewriteCond %{REQUEST_FILENAME} -f [OR]
RewriteCond %{REQUEST_FILENAME} -d
RewriteRule ^ - [L]

# Route everything else to index.php so your router can handle the random string
RewriteRule ^(.*)$ index.php?route=$1 [L,QSA]