The interactive toy I made was a music box which plays a song and lights up when you open the lid. My initial idea was to have a servo motor which turned a small toy as well, but I realized that you cannot implement both the tone() and PWM functions onto one Arduino. The intended user is any child over the age of 1 with basic motor skills to open a box. Since this is a pretty simple and intuitive action, the design of my toy took the limitations and capabilities of an infant into account.
I tested the toy on my little sister, who is 1.5 years old. My other little sister, who is 6 years old, helped me decorate the box. As you can see in the video, she was interested at first, but after playing with it a little while she kept trying to press the LEDs and remove the top of the box to reveal the inner workings underneath, which poses a problem for young children as there are many small choking hazards.