For our playful creations, we built two Minions. One Minion tracks where you are and follows you, keeping a certain distance away. The other Minion is a similar concept to a wind-up car. After pushing a button to start recording its motion, the Minion keeps track of motor rotation so it can play back the movement after the button is pushed again, signaling the end of the recording. Both Minions were built with almost the exact same body structure (same frame and motor location, etc.).

The following Minion uses two ultrasonic sensors to determine distance and a semblance of direction. Using the law of cosines, we can determine if the robot needs to turn one way or the other based on the angles of the triangle that is formed (using the two ultrasonic sensors and the object they are looking at as the vertices of the triangle). It runs continuously, only stopping its motion when it is at the desired distance away from the target, or the stop button on the EV3 is pushed. This is a main shortcoming of the toy, as when children want to stop playing with it, the Minion continues to follow them. The tracking itself is only as good as the ultrasonic sensors, so it does not respond well to quick lateral movements.

The windup car Minion continuously reads the change in motor rotation every fifth of a second, storing the values in an array while it is recording the motion. Through experimentation, we discovered the relationship between the speed value input for the motor and the angular velocity it exhibits. Using this information and the list of motor rotation values, the Minion can play back all of the values that were recorded at almost the same speed they were recorded. The result is a very good replica of the motion that was recorded. A shortcoming of this toy is that the wheels were sliding instead of rotating when many children used the toy. The motion from the sliding wasn't recorded and therefore the Minion did not move as the children expected. Also, in order to make the button easier to see and use, gears and wheels were placed on top of it through a rod, but the gears and wheels slipped down the rod, making it more different to activate the button.

We asked the children multiple questions, and also observed their behaviors while interacting with our toys. We asked all of the children if having the Minion design on the toys made them more fun to play with and if they recognized the character. All of them found the Minion design to be more engaging than no design and all but the youngest recognized the character. The majority of children enjoyed both toys. We asked for each toy on a scale of 1 - 5 how much fun they had and the lowest response was a 3, with most being 4s. We also asked which Minion they found to be more fun/more engaging. The younger children mostly found the follower Minion to be more fun, while the older children, who generally had more success using the windup car Minion, said the opposite. From the sheets of paper that the visitors filled out, most had filled in or circled the fun smiley face.

For behavioral observations, some of the younger children were scared to interact with the follower Minion, and they were more likely to get bored while the windup car Minion was replaying what they recorded. The older children had an easier time understanding that the wheels needed to turn for the windup car Minion to work properly and then enjoyed playing with that Minion a lot. Some children had the follower Minion follow them walking around our area, but many others, sometimes after realizing what the Minion was poor at tracking, had more fun using their hands to "direct" the Minion where to go.

To change our Minions to make them even more enjoyable, we have a few plans.

• Putting a button on the following Minion so that it can start and stop
• Making the button on the windup car Minion easier to use
• Making the maze/roadmap bigger and more interesting
• Try to improve the accuracy of the tracking by the following Minion
• Change Minion design using the hats to look more professional
• Make easier to turn wheels using robotic solution OR explain/demonstrate easier way to make wheels turn when using Minion