The star() function created for this example is capable of drawing a wide range of different forms. Try placing different numbers into the star() function calls within draw() to explore. 

def setup():
    size(640, 360)


def draw():
    background(102)

    pushMatrix()
    translate(width * 0.2, height * 0.5)
    rotate(frameCount / 200.0)
    star(0, 0, 5, 70, 3)
    popMatrix()

    pushMatrix()
    translate(width * 0.5, height * 0.5)
    rotate(frameCount / 50.0)
    star(0, 0, 80, 100, 40)
    popMatrix()

    pushMatrix()
    translate(width * 0.8, height * 0.5)
    rotate(frameCount / -100.0)
    star(0, 0, 30, 70, 5)
    popMatrix()


def star(x, y, radius1, radius2, npoints):
    angle = TWO_PI / npoints
    halfAngle = angle / 2.0
    beginShape()
    a = 0
    while a < TWO_PI:
        sx = x + cos(a) * radius2
        sy = y + sin(a) * radius2
        vertex(sx, sy)
        sx = x + cos(a + halfAngle) * radius1
        sy = y + sin(a + halfAngle) * radius1
        vertex(sx, sy)
        a += angle
    endShape()