because it works. And it must work extremely well since there are clones of it. Edit: To make game out of that would be hard enough since its custom animation

because it works. And it must work extremely well since there are clones of it. Edit: To make game out of that would be hard enough since its custom animation make to look like game. Plus the make money on repetitive game-play, puzzles would not keep players hooked and paying to skip the grind.