How to track site progress in Edge Animate

All-

I'm building a site in Edge Animate where options are presented to the user as they go.  It's sorta game like where you can't get to the next unit until you've gone through the prev etc.  What I have to do now is track the user's progress so they pick up where they left off.  In other words, if they've gone through two units the start with the third and not at the beginnig.  Hope this makes sense

Thanks!