particularly intrigued by the "M heart 8" puzzle that was mentioned at some point in the movie. It basically is a capital M above a heart which in its bottom end is crossed by a straight line and beneath it is the number 8. This is a symbolic symmetry of some kind and you are supposed to find the next symbol that goes under 8.
It is really hard, but once you find it or you are told the answer it is pretty amazing. It is actually brilliant!
See the solution that a gave a friend of this blog HERE.