Image Reveal w/Quiz

As a corollary to Nedim's solid answer, I've found a simple method for reveal to be removing squares that cover an image.

The solution commonly offered is to take the large image you want to reveal, segment it out into many pieces, arrange them on a slide to reform the image, and then set their default state to Hidden or something similar, revealing them according to certain triggers. This is fine but people tend to see the amount of work involved in segmenting one picture into many small pieces. What if you want to change the picture? What if you want a different number of pieces?

If you instead cover up the large image with some simple squares, those can be hidden or animated away to slowly reveal the whole image underneath, and requires less work.

Bonus points if instead of simple squares, you cover the large image with buttons, and the learner uses those buttons to attempt certain questions. This allows for learners who answer incorrectly to attempt a different question or reattempt the same, and even allows for certain questions to correspond to certain parts of the underlying image.