The crew at the Sherlock Holmes themed escape room in London posted a couple of photos on their instagram. Squinting at a tiny screen didn’t work so well for me, so I had to try and make an interactive version. At first I used regular old hotspots, but then changed to using shapes so that I could highlight the object after it was found. I didn’t realise until now that a shape with no border and no fill could still be responsive to clicks.
I used a giant hotspot underneath all the shapes, so that the cursor switching to a hand was not an extra clue.
Apart from Spot-the-Difference, this setup could easily be used for hazard identification etc.
The sparkly noise when you locate a change is from Freesounds.org https://freesound.org/people/Soughtaftersounds/sounds/145459/