The game is finally playable, but there certainly are many areas in which it can be improved. If you're willing to toy with the concept of 2048 some more, consider some of the following tasks:
Add more animations—they do wonders in terms of perceived interactivity.
As an additional motivational factor, add a score counter and the related infrastructure (for instance, the ability to save high scores and transmit them to the global server-side leaderboard).
Tweak the game rules so that they are exactly like the original 2048 game.
For a more mind-bending experimentation, build an algorithm that predicts fruitless game sessions in advance. As a player, I would positively love to receive a notification that reads, "No matter what you do, in 7 turns it's over for you, thanks for playing."
Change the rules completely. Add a multiplayer arena death match mode—be creative.