As Theta 2 rotates from 0 to 360 degrees, Theta 3 and Theta 4 go through one period of motion. Link 4, which is a rotating and sliding bar, slides in and out of the body as the neck, and leads to the movement of the head and arms.
As shown below, the vertical movement of the head and hands is very similar, which makes sense because they are both attached to Link 4. Therefore, the bulk of the peek-a-boo motion is a result of the arm's horizontal movement. Bevo's eyes are each 1 cm away from the midsection, meaning that Bevo is covering his eyes between 167° and 323° when the x position of the hand is less than 1 cm.
