The parameter p increasing from 0 to 1 is the probability that a hexagon is open. Closed hexagons are shown in blue, and open ones in yellow when they are connected to the left boundary, and gray otherwise. The increase of p slows down when it reaches the critical value, which is equal to 1/2. The graph shows the rsize of the percolation cluster (the set of open hexagons connected to the left boundary), divided by the number of open hexagons, as a function of p.