Origami Probability from Brilliant.org

From Brilliant.org https://brilliant.org/community-problem/origami-probability/?group=3kpZEk8aGdfD. A square sheet of paper has its center marked with point O . A random point is uniformly chosen on the square paper, and this point is labeled P. The paper is then folded so that point P coincides with point O. Let the probability that a pentagon is formed after the fold be N. Find the value of N. Where should P be located? What would be the shape of this region? Before you drag point P around, predict the shape of the region. Then, drag P slowly. When P is colored BLUE, a pentagon is formed.