Google Sign-In is a secure authentication system that reduces the burden of login for users, by enabling them to sign in with their Google account.
jQuery is a JavaScript library which is a free, open-source software designed to simplify HTML DOM tree traversal and manipulation, as well as event handling, CSS animation, and Ajax.
Nginx is a web server that can also be used as a reverse proxy, load balancer, mail proxy and HTTP cache.
PHP is a general-purpose scripting language used for web development.
Underscore.js is a JavaScript library which provides utility functions for common programming tasks. It is comparable to features provided by Prototype.js and the Ruby language, but opts for a functional programming design instead of extending object prototypes.
VK is a Russian online social media and social networking service.
Yandex.Metrica is a free web analytics service that tracks and reports website traffic.