// https://en.wikipedia.org/wiki/Regular_polygon#Regular_star_polygons
// https://mathworld.wolfram.com/StarPolygon.html

Canvas.setpenopacity(1);

// 2 < 2q < p, gcd(p, q) = 1

// how many points
const p = 7; // min=5, max=30, step=1
// how many points to skip when connectingh
const q = 2; // min=2, max=15, step=1
const radius = 100; // min=10, max=100, step=10

const sides = p;
const angle = 360 * q / p;

// Global code will be evaluated once.
const turtle = new Turtle();

// center horizontally
turtle.penup();
turtle.goto(0, -radius);
turtle.right(angle/2);
turtle.pendown();

const length = radius*Math.sin(2*q/p*Math.PI)/Math.sin((p-2*q)/(2*p)*Math.PI);

// The walk function will be called until it returns false.
function walk(i) {
    turtle.forward(length);
    turtle.right(angle);
    return i < sides;
}