Spot the differences
This is a simple example of the well known observation game. I manipulated the image using Photoshop and then used hotspots, triggers, correct object states, hover reveals and a single scoring variable to complete the task, all on a single slide with layers. In hindsight I should have added a zoom & pan capability as this particular illustration is only viewable on a large screen.
P.S. Sorry Mike Hall I didn't seek permission to use your beautiful illustration but hope the credit link to your site will attract work!
P.P.S. Let me know in the comments if you find all 11 differences without cheating!