In order to see the difference between group velocity and phase velocity, let's make a wave group. To make this experiment work, we need to make "enough waves to form a group". So we will increase the number of wave making rods to four, and make four wavelengths of wave at once. If you create the waves in the upper right corner, one of the wave groups spread from the wave source toward the bottom left. Of course energy is also being transmitted in that direction. Inside the wave group, the waves' phase (their bow and trough pattern) moves from bottom right to top left. This pattern does not leave the wave group's area, so waves form one after the other at the bottom right of the group and disappear one after the other at the top left.