The jsbin you linked does not work on my computer, so there might be other problems.
Anyway, to make the Background move horizontally in your game, you find the function function Background(), and change this.y asignations to this.x (for example, this.y += this.speed would become this.x += this.speed).
The jsbin you linked does not work on my computer, so there might be other problems.
Anyway, to make the Background move horizontally in your game, you find the function
function Background()
, and change this.y asignations tothis.x
(for example,this.y += this.speed
would becomethis.x += this.speed
).