The Eye-Pentagon Construction
With a ruler and compass, an eye is easy to construct, leading to a regular pentagon construction. First draw a unit circle centered at O, the pupil. With centers at the top and bottom of the pupil, draw two circles of radius 2 to form the eyelids. Using the top of the pupil (A) as the center, draw an arc of radius 1 (AO) to intersect the upper eyelid at B. With C as the left corner of the eye, draw an arc with radius OC, and then a larger arc with radius BC. Draw a final arc with radius BC centered at O. Connect the intersection points for the pentagon.