Hey, author here! I'm pretty overwhelmed that this made it to the top of HN without me even thinking of posting it here :) I made this game as a fun weekend project, inspired by another game called 1024 ( https://itunes.apple.com/us/app/1024!/id823499224 ) and a spinoff called 2048 ( http://saming.fr/p/2048/ ). I did mine to add animations to the latter, which was a bit hard to play without them. I discovered Threes…
Good for beta testing it.
Unlike with Threes, there's no real reason to use numbers since they're all powers of 2. If you used letters (A, B, C, ...) you could market it to non-HN sorts, and have a version of the game in a 5x5 grid, or, more to the point, in a 6x6 grid with letters A to Z. Most people in the world know the order of letters in English.