I have mastered the art of controling when the user can click the "Next" button, but how do I put triggers/conditions on the "Previous" button. It's a completely optional button, so there is no exact when to add to the trigger.
My issue is that when the users are going through the content on one slide, they click objects on the slide that takes them to layers. They click the "X" that I have placed to hide that layer and then the object shows the "visited" state. Only after they have clicked all objects can they click on the "Next" button. But they can click "Previous" at any time, and if they do so during one of the layers, when they come back, the layer shows on top of the base slide.
What's the quickest way to fix that?