The challenge in Flow Rush is crowd control. The little men will start their run from the start at each level. Moreover, they can run either in one single-colored crowd or in two different groups of different colors. As you approach the gate, react quickly to the value that appears on it and direct the crowd to where it can grow rather than shrink. At the finish line you will have to break barriers and if the crowd is small, you will not be able to complete the level in Flow Rush. A quick reaction will save you.
