Storyline 360

Trying to have a "Next Button" that is hidden on the base layer appear only when all slide layers have been visited (I have 11 layers plus the base layer all of which have one or more hotspots, animations etc.)

I tried to extend the timeline out to 30 seconds and have the button appear at the end of the timeline, which works just fine, but for example if the does interact at all with the base layer and each layer does have a way to go back to the base layer, but it seems that the timeline resets (tested this by doing nothing on the base layer vs. interacting and going back to base layer) when moving away and back to base layer.

Is there an easy way to accomplish this or do I need to create visited states for every object and then have the button  appear when all states are visited?

Hope my explanation makes sense, .story file attached, section I am referring to is Scene 4 slide 4.3