Deep beneath the ocean waves, you discover a glowing reef where every fish is actually a two-dimensional shape swimming through the water. Triangle fish dart between the coral, rectangle fish glide along the sandy floor, and square pufferfish float carefully in perfect angles. To unlock the submarine hatch and escape, you must study the fish and identify which shapes belong to larger families, noticing how some fish fit into more than one group at the same time. Only by correctly classifying the deep sea shapes can you swim safely back to the surface.