Mark an object as completed (using a green check mark)
At one point in a course I'm creating, the learner is asked to explore 4 different objects. When they click on one, they learn about it, one at a time (on different slides). When they've completed one and click back to the screen where they're all listed, I'd like a green check mark to appear next to the one(s) they've completed until they've explored all 4. So, until all 4 have a green check mark next to them.
I created a check mark next to each object on the main slide and set the initial state to hidden. But, I cannot figure out how to change the state of the green check to normal once the learner click has explored one and gets back to the main slide where all 4 are listed. I know I learned how to do this, but my memory is failing me.
I've attached a screen shot. Basically, 2.2 is the main slide. There will be a button to click from 2.7, 2.8, 2.9, and 2.10 to get back to 2.2. When they do, I'd like the green check to appear so they don't click the same one twice.
I appreciate any guidance on how to get this to function the way I see it in my mind.