Pistons is the 31st Expert stage in Challenge Mode and World 8-1 in Story Mode.
The stage has a starting platform that leads to a ramp, which narrows and goes up toward a larger platform. This platform has the outline of a pentagon and contains triangular holes of equal size that are separated by narrow pathways. Each hole lies above a triangular shaped piston that spikes up and down periodically. The center-most piston moves up first, followed by its surrounding pistons, and so on to create a wave-like pattern that travels to the outer edges of the pentagon. The goal is located on a small extended area at the opposite end of the pentagon.
There is only one goal, the blue goal. Roll up the ramp, and proceed slowly along one of the narrow paths. When the wave of pistons gets close to you, make sure you are waiting at one of the intersections before continuing onward. Turn at intersections as necessary until you get to the goal.
You can also fall through one of the holes and land on a piston. This strategy is slower and more risky because you need to go airborne to access the goal. When it springs you up, use the map to guide the ball toward one of the intersections, bounce off, and land in the goal.