This site uses Google Analytics to log anonymous data. Like what? Like which pages are visited, when they are visited, and which towns or cities people are (probably) visiting from. It doesn't track things like your name or address, and it can't because your computer doesn't give out that kind of information.
It also gives your computer scribbled notes that your computer repeatedly sends back. What?
On the internet, clicking a link is like mailing a letter where the return address is a bunch of letters and numbers with no name. The letter you get back is one web page, and you must send a new letter to request each page. One person might send these requests from different addresses, and different people might request the same page from the same address, which means the website doesn't even know whether two requests came from the same person. They compensate for this by giving your computer notes in a text file that your computer must send back with Every. Single. Request. This allows the site to keep track of information such as whether you have read this message already and which pages are viewed the most. The string of scribbled notes is called a COOKIE. Surprise.
It also allows advertising companies to do the same thing, and each company might do this at many websites. Do they/you know everything about me?
The Internet is engineered to allow your computer to communicate with "something". This is usually a website, or a thing with a website address (like "cesoid.com"). Your computer runs software called a "browser" (such as Chrome) to do this. Browsers only send cookies back to websites that created them. Even an advertisement appearing on cesoid.com has separate cookies that your browser would not send to cesoid.com, and your browser would not send cookies from cesoid.com to the advertising website. For these reasons, nobody can use a cookie that tells them everything that you're doing. So how do they seem to know exactly what to advertise to me?
Advertisers seem to know so much about you because, even if they don't know who you are and can't read cookies that belong to other websites, a lot of websites allow them to send and receive a cookie, which means they have collected a long list containing many of websites you've visited, and also they share a lot of (often anonymous) information with other companies. It's not so much that cookies give them new kinds of information, as it is that many of the websites you visit add a little bit of information, and those websites share information about you to advertisers, even if it is just which site you're visiting, and cookies allow them to tell which bits of information pertain to the same person.
Advertisers don't need your name or your ID number to sell you something, and they don't want it, because having that information subjects them to more regulations, but, more importantly, your name doesn't tell them what you want to buy.
How to play: Use your arrow keys (or WASD keys) to move the tiles. When two tiles with the same number touch, they merge into one!