Create the number one ('1') with only outlines, without any internal color. The design should be simple, playful, and attractive to young children. Add fun sections inside the number using wavy or zigzag lines, ensuring that children can color each section differently. Incorporate elements related to children's toys (like blocks, balls, or teddy bears) or cute animals to make the number more appealing. Make sure the entire design is just lines—no colors—so it can be used in a coloring book.