CROSSES
My main idea is: try random moves for the opponent and see if we get the correct score. Then, I only concentrated on searching for the pseudorandom number generator seeds that work.
BRIGAMI
My solution is greedy. The first approach: always choose a cut that cuts off the largest area (gave me a score of 200). Then I changed it to: maximize area cut off divided by extra cut length (outside the inside polygon), to get 210.