let radius = 100;

let p;

​

function setup() {

  createCanvas(400, 400);

    p = createVector(width/2, height/2);

}

​

function draw() {

  background(220);

    stroke(0);

    ellipse(p.x, p.y, radius);

    //handle

    let x_comp = mouseX - p.x;

    let y_comp = p.y - mouseY;

    angle = atan2(y_comp , x_comp);

    if (angle < 0)

        angle = (2*PI) + angle;

    //angle = (2*PI) - angle;

    line(p.x, p.y, mouseX, mouseY);

    console.log(angle);

}