Problem with step slider

Hello everyone, I have used @PixelGeek way to create a step slider (described in this video: The problem is that with this way I lose two slides on tablet and mobile. Any workaround?

Here is my site Read-Only:

And here is my live link:

Hello @Jim_Kalligas

In this case I would suggest that instead of using the 33.33% on the mask of the slider to do it in the slides.