Question 15
Every cell is gray or white. Every minute all cells update simultaneously using their eight surrounding neighbors, including diagonal neighbors: a gray cell with fewer than 2 gray neighbors becomes white; with 2 or 3 it stays gray; with more than 3 it becomes white. A white cell with exactly 3 gray neighbors becomes gray. Otherwise its color stays unchanged. The example shows one minute.
Starting with this board, how many gray cells remain after two minutes?
Starting with this board, how many gray cells remain after two minutes?