8/10 (better than the 1st one). Here's why:

The acting in CUBE PART 2: HYPERCUBE is still weak, but this time, there's not a single actor to save the movie. Let me rephrase that. There's not a single actor to make the movie better. Script writers Sean Hood, Ernie Barbarash and Lauren McLaughlin also focus more on the survival instincts than existensialism, which once again result in thrilling moments. However, they add math and physics, making this sequel even more of a brain challenge. Showing the outside of the Cube was a bad idea because the mysteries in the 1st movie didn't need to be solved. But you know what? What we see here at the end creates more questions than answers (putting the explanatory alternative ending aside), so it's not really answering anything.