The point of this game is for the hunter to catch the prey as quickly as it can. The hunter is able to move twice as fast as the prey,but it changes direction only by bouncing off a wall. The prey, on the other hand, can move in whichever direction it wants provided it doesn't pass through a wall. The hunter catches the prey by building horizontal and vertical walls at its current position to get close to the prey and trap it.

Video: https://youtu.be/_-mJ8Wv005o