Yeah, so I just played this game. And then the Game Over screen appears before I can finish the game. You can see in later pics that I can continue until I finally got to the true ending!
https://imgur.com/a/spNMVDT
Hey there! I've pushed a new version (1.0.3) that should fix this.
The problem was due to how the game was initialised from a previous save. Tile’s values would be set as a String instead of a Number. Then in the end of the game, when the grid is full, the game would incorrectly compare String values (from tiles restored from a previous save) with Number values (from tiles created during the game after loading).