let startAngle = (180 / 13) * (5/2) - 90; rotation

let openAngle = 180 / 13; 

​

function setup() {

  createCanvas(500, 500);

  background(200);

}

​

function draw() {

  background(220, 210, 190);

​

  let centerX = width / 2;

  let centerY = height / 2;

​

  let triangleNumber = map(mouseX, 50, 450, 1, 9);

​

  // Call the drawAFoldingFan function

  drawAFoldingFan(centerX, centerY, triangleNumber, startAngle, radius);

}

​

// Define the drawAFoldingFan function

function drawAFoldingFan(centerX, centerY, triangleNumber, startAngle, radius) {

  translate(centerX, centerY); // Move to the fan's center position

​

  // Draw the specified number of fan leaves

  for (let i = 0; i < triangleNumber; i++) {

    let angleOffset = i * radians(openAngle);

    push();

    rotate(angleOffset + radians(startAngle)); // Rotate each leaf around the center

     fill(200, 100, 100);

    drawFanLeaf(openAngle, radius); 

    pop();

  }

}

​

// Define the function "drawFanLeaf"

function drawFanLeaf(openAngle, radius) {

  let Bx = -radius * tan(radians(openAngle / 2)); //left

  let By = -radius;

  let Cx = radius * tan(radians(openAngle / 2)); //right

  let Cy = -radius;

​

  //Fan leaf model

  beginShape();

  vertex(0, 0); 

  vertex(Bx, By); 

  vertex(Cx, Cy); 

  endShape(CLOSE);

}

​