How do I make a invisible button?

I have a problem, I want to make the buttons as sprite, to be more beautiful, only doing so, he note insert more action in the array ... I've tried to leave the button on top of the sprite and leave initial invisibility as invisible, but does not work, anyone know how to do this?

My project: mega.nz/#!fIIQjSZY!c6G7RRBZQYqGH7oj2wBn7V1JsjXVReLYeeLygX539xQ

You can just choose on clicked Sprite with mouse object if you want Sprite as button, is that good enough?

It should work with

Touch -> On touched object -> Do this (Button)

Button itself -> collisions enabled, Set invisible