let bright = 0; 

​

function setup() {

  createCanvas(500, 500);

  dark = color(0);

  light = color(255, 204, 0);

  serial = new p5.SerialPort();

  serial.open('/dev/tty.usbmodem2101');

}

​

function draw() {

  background(0);

  fill(255, 43, 28);

  stroke(255);

  strokeWeight(6);

  ellipse(250,250,250,250);

  stroke(255);

  strokeWeight(3);

  noFill();

  ellipse(mouseX, mouseY, 10, 10);

}

​

function mouseClicked(){

  bright = floor(map(mouseY, 0, 500, 0, 500));

  bright = constrain(bright, 0, 255);

  serial.write(bright);

  console.log(bright);

}