function setup() {

  createCanvas(400, 400);

  background(100);

  frameRate(60);

}

​

function draw() {

  // Brush

  if (mouseIsPressed) {

    brush(mouseX, mouseY);

  }

  // Erase

  if (keyIsPressed) {

    background(100);

  }

}

  //Brush

function brush(X, Y) {

  noStroke();

  rect(X,Y,random(40),random(40));

  rect(X+20,Y+20,random(40),random(40));

  rect(X-20,Y-20,random(40),random(40));

  translate(width / 2, height / 2);

shearX(PI / 4.0);

  stroke(random(255));

  fill(random(150), random(150), random(150));

  ellipse(X, Y, random(50), random(50));

  ellipse(X+50, Y+50, random(50), random(50));

  ellipse(X+100, Y+100, random(50), random(50));

  ellipse(X+150, Y+150, random(50), random(50));

  ellipse(X-100, Y-100, random(50), random(50));

  ellipse(X-150, Y-150, random(50), random(50));

  ellipse(X-50, Y-50, random(50), random(50));

}

​