var rainbow; // toggle for rainbow brush

​

function setup() {

  createCanvas(400, 400);

  background(255);

  colorMode(HSB);

  b = color(0, 0, 0);

  rainbow = 0;

}

​

function draw() {

  if (mouseIsPressed) {

    // Reset Button

    if (mouseX > 20 && mouseX < 80 && mouseY > 300 && mouseY < 330)

      background(255);

    // Green Button

    if (dist(30, 50, mouseX, mouseY) < 10) {

      b = color(120, 100, 100);

      rainbow = 0;

    }

    if (mouseX > 20 && mouseX < 40 && mouseY > 100 && mouseY < 120) {

      rainbow = 1;

    } else if (mouseX > 20 && mouseX < 40 && mouseY > 140 && mouseY < 160) {

      rainbow = 2;

    }

  }

​

  // Console Panel

  fill(150);

  strokeWeight(1);

  rect(0, 0, 100, height);

​

  // Color Buttons

  fill(120, 100, 100);

  ellipse(30, 50, 20);

​

  rect(20, 100, 20, 20);

  for (var i = 0; i < 18; i++) {

    stroke(i * 16, 100, 100);

    line(i + 21, 101, i + 21, 119);

  }

​

  rect(20, 140, 20, 20);

  for (var i = 0; i < 18; i++) {

    stroke(i * 16, 100, 100);

    line(20, i+141, 40, i+141);

  }

  // Reset Button

  fill(100, 120, 255);

  rect(20, 300, 60, 30);

  fill(0);

  text("RESET", 30, 320);

​

  // Draw

  if (rainbow == 1) {

    b = color(map(mouseX, 100, width, 0, 360), 100, 100);

  } else if (rainbow == 2) {

    b = color(map(mouseY, 0, height, 0, 360), 100, 100);

  }

  fill(b);

  stroke(b);

  strokeWeight(3);

  if (mouseIsPressed)

    line(pmouseX, pmouseY, mouseX, mouseY);

}