Only '2' tiles spawn. To match the original game, both '2' and '4' tiles should spawn

[defensem3ch]

trafficstars

[ehmry]

I didn't know there was an official game.

[defensem3ch]

Perhaps I should rephrase it to "original game" which can be found here: https://github.com/gabrielecirulli/2048

However on this index.html page it states:

Note: This site is the official version of 2048. You can play it on your phone via http://git.io/2048. All other apps or sites are derivatives or fakes, and should be used with caution.