The universal (based on commonly used) HD Resolution has an aspect ratio of 16:9 . With that resolution, many devices will fit on your game.
I'm not sure what aspect ratio that game you linked here but I know it has an HD resolution. And the nearest aspect ratio I can think of for that video... is 16:9.
As I said, that is a common aspect ratio for a landscape game/movie.
Now for the resolution size. The HD resolution size for a 16:9 aspect ratio is (1280 x 720).
So I hope you found what you need there.