NGINX Splash Screen

I need a 'Splash Screen System', created for Nginx which is similar to what you have when you go to a cloudflare powered site.(We are just checking your browser.... Please wait for x seconds while we verify you are a real user...) This should be written in any language you want, as long as it works, I should be able to set a 'default splash screen' in a [login to view URL] file then do individual splash screens for each website by overriding it in the sites '[login to view URL]' server{} bracket and customize the amount of time it shows for.