CDP illusion problems are bogus. Their "illusion" problems are nothing but incorrectly drawn cubes. You may encounter some obscure questions on the pat but, unlike the "illusion" cubes, they are legitimate questions that can be figured out with a bit of extra attention (I got one the cube counting section that had a cube missing in a letuce of cubes however it was hard to spot at first since there was a lot going on in the figure and the other cubes were arranged to distract from that spot-- its hard to explain but it was funky looking. I also got a problem on the hole punch section where the paper was folded in thirds several times. I have never seen anything like it on any of the practice tests that I took (cdp and 1 achiever) and did not think that that that that was possible, but there it was...I'm pretty sure I got that one wrong 🙁