[bug] for mobile browsers (like Android or iPhone), the footer of "Powered by [Casdoor logo]" cannot be see directly in the screen

For the login page like: https://door.casdoor.com/, for mobile browsers (like Android or iPhone), the footer of "Powered by [Casdoor logo]" cannot be see directly in the screen. The user has to scroll down a little bit to see the footer. We want the footer to directly shown in the bottom of the page at first page load of login UI.