let song;

let amplitude;

​

let Particle = function(position) {

  this.position = position;

  this.speed = createVector(1, 1);

  this.accelerationX = 0;

  this.color = [0, 0, 0];

  this.lifetime = random(200, 1500);

  this.start = performance.now();

  this.size = random(10, 15);

  this.draw = function() {

    blendMode(ADD);

    circle(this.position.x, this.position.y, this.diameter);

    fill(this.color);

  }

  this.update = function (energy) {

    let windDirection = (mouseX - windowWidth / 2) / (windowWidth / 2);

    this.accelerationX = random(-1, 1);

    this.speed.x = max(min(this.speed.x + this.accelerationX, 2 + 1.5 * windDirection), -2 + 1.5 * windDirection);

    this.position.x += this.speed.x;

    this.position.y -= this.speed.y * (energy / 255 * 155 + amplitude.getLevel() * 100) / 255 * 10;

    if (this.position.x < 0) {

      this.position.x = windowWidth;

    }

    if (this.position.x > windowWidth) {

      this.position.x = 0;

    }

    if (this.position.y < 0) {

      this.position.y = windowHeight;

      this.lifetime = random(200, 1500);

    }

    if (performance.now() - this.start > this.lifetime) {

      this.position.y = windowHeight;

      this.lifetime = random(200, 1500);

      this.start = performance.now();

    }

    this.diameter = this.size * ((this.lifetime - (performance.now() - this.start)) / this.lifetime);

    this.color = [

      map(energy / 255 * 155 + amplitude.getLevel() * 100, 0, 255, 0, 43), 

      map(amplitude.getLevel(), 0, 0.6, 255, 0), 

      energy

    ];

  }

}

​

function setup() {

  createCanvas(windowWidth, windowHeight);

  colorMode(HSB);

  noStroke();

  song = loadSound('dies_irae.mp3');

  fft = new p5.FFT();

  amplitude = new p5.Amplitude();

  fft.setInput(song);

  positionParticles();

}

​

function mousePressed() {

  if (song.isPlaying()) {

    song.stop();

  } else {

    song.play();

  }

}

​

function draw() {

  blendMode(BLEND);

  background(0, 60);

  if (!song.isPlaying()) {

    textSize(14);

    fill(255);

    textAlign('center')

    text('Move mouse to control wind direction', windowWidth / 2, 50);

    textSize(14);

    fill(255);

    textAlign('center')

    text('Click to begin', windowWidth / 2, 70);

  }

  textSize(32);

  fill(255);

  textAlign('center')

  text('Verdi: Dies Irae', windowWidth / 2, windowHeight / 2);

  fill(0);

  drawParticles();

  let spectrum = fft.analyze();

  updateParticles(spectrum);

}