let radius; // radius of the circle

let isDragging = false; // flag to indicate if the mouse is being dragged

​

function setup() {

  createCanvas(400, 400);

  background(220);

}

​

function draw() {

  if (isDragging) {

    // update the radius based on the distance between the center and the mouse position

    radius = dist(centerX, centerY, mouseX, mouseY);

    // draw the circle with the current radius

    ellipse(centerX, centerY, 2 * radius, 2 * radius);

  }

}

​

function mousePressed() {

  // set the center of the circle to the current mouse position

  centerX = mouseX;

  centerY = mouseY;

  // set the initial radius to 0

  radius = 0;

  // set the dragging flag to true

  isDragging = true;

}

​

function mouseReleased() {

  // set the dragging flag to false

  isDragging = false;

  // draw the final circle with the last set radius

  ellipse(centerX, centerY, 2 * radius, 2 * radius);

}

​