That's correct. Ideally you'd want a screen with double the dimensions so that you can designate a portion of it with uniform probability of any location havin

That's correct. Ideally you'd want a screen with double the dimensions so that you can designate a portion of it with uniform probability of any location having Waldo. And my model has it so that (for the second challenge) Bob learns the position of Waldo relative to the screen, but not the position of Waldo relative to the page, which is what we mean by "finding Waldo". And, of course, on that challenge, Bob would not get to learn the position of the page relative to the screen (which would allow him to "find Waldo").