// https://jonfroehlich.github.io/

​

let diameter = 30;

function setup() {

  createCanvas(600, 400);

}

​

function draw() {

  // background(220);

  if(mouseIsPressed){

    // if the mouse is pressed, change paintbrush to blue

    fill(66, 194, 245, 128);

  }else{

    // if mouse not pressed, change paintbrush to purple

    fill(200, 0, 200, 128);

  }

  noStroke(); // turn off outline

  // make diameter of paintbrush proportional to mouse speed

  // that is, the mouse brush is the distance between the

  // last mouse location and the current mouse location

  diameter = dist(mouseX, mouseY, pmouseX, pmouseY);

  // draw the circle (the "paintbrush") at the current mouse location

  circle(mouseX, mouseY, diameter);

}

​

function keyPressed(){

  print(key);

  if(keyCode == DELETE){

    background(0);

  }else if(key == 'a'){

    diameter = diameter + 5;

  }

}