Isn't this illegal?

Actually it does look better than the original. Just look at the characters in the first picture, they all look less pixelated a more detailed than the characters and items in MS. Maybe they are actually ripping off the mobile games and not the main game and maybe this game looks better because MS mobile games overall look better than the original game too, which would be shamefull.

I assumed Soph was referring to the promotional art.

In game its entirely different, maple sprites are more pixelated, while this game looks smoother. Personally I prefer the pixelated look more, its just what I'm used to.