I think you could improve this test by at the very least not saying "correct". There were many cases where I spotted the difference and disagreed. Equally, the

I think you could improve this test by at the very least not saying "correct". There were many cases where I spotted the difference and disagreed. Equally, there were cases where I simply guessed and got lucky or unlucky. You could make this test much better by making the user click near the difference. This both removes the subjectivity and makes it much less likely to simply guess.