createCanvas(400, 400);

}

​

function draw() {

  background(255);

  fill('#0af')

  circle(200,200,300)

   push();

  translate(width * 0.5, height * 0.5);

  fill(255)

  let t=3

  if(mouseX/20>t)

    {

      t=mouseX/20

    }

  polygon(0, 0, 150,t);

  pop();

    push()

   fill(0)

     text((t*sin(180/t))+3,200,200)

  pop()

text('the value is less acurate when sides are unequal',100,370)

}

​

function polygon(x, y, radius, npoints) {

  let angle = TWO_PI / npoints;

  beginShape();

  for (let a = 0; a < TWO_PI; a += angle) {

    let sx = x + cos(a) * radius;

    let sy = y + sin(a) * radius;

    vertex(sx, sy);

  }

​

​

 endShape(CLOSE); 

}