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body {
  margin: 0;
  height: 100vh;
  overflow: hidden;
  background: black;
}

/*--------------------
Vars
--------------------*/
const deg = (a) => Math.PI / 180 * a
const rand = (v1, v2) => Math.floor(v1 + Math.random() * (v2 - v1))
const opt = {
  particles: window.width / 500 ? 1000 : 500,
  noiseScale: 0.009,
  angle: Math.PI / 180 * -90,
  h1: rand(0, 360),
  h2: rand(0, 360),
  s1: rand(20, 90),
  s2: rand(20, 90),
  l1: rand(30, 80),
  l2: rand(30, 80),
  strokeWeight: 1.2,
  tail: 82,
}
const Particles = []
let time = 0
document.body.addEventListener('click', () => {
  opt.h1 = rand(0, 360)
  opt.h2 = rand(0, 360)
  opt.s1 = rand(20, 90)
  opt.s2 = rand(20, 90)
  opt.l1 = rand(30, 80)
  opt.l2 = rand(30, 80)
  opt.angle += deg(random(60, 60)) * (Math.random() > .5 ? 1 : -1)
  
  for (let p of Particles) {
    p.randomize()
  }
})


/*--------------------
Particle
--------------------*/
class Particle {
  constructor(x, y) {
    this.x = x
    this.y = y
    this.lx = x
    this.ly = y
    this.vx = 0
    this.vy = 0
    this.ax = 0
    this.ay = 0
    this.hueSemen = Math.random()
    this.hue = this.hueSemen > .5 ? 20 + opt.h1 : 20 + opt.h2
    this.sat = this.hueSemen > .5 ? opt.s1 : opt.s2
    this.light = this.hueSemen > .5 ? opt.l1 : opt.l2
    this.maxSpeed = this.hueSemen > .5 ? 3 : 2
  }
  
  randomize() {
    this.hueSemen = Math.random()
    this.hue = this.hueSemen > .5 ? 20 + opt.h1 : 20 + opt.h2
    this.sat = this.hueSemen > .5 ? opt.s1 : opt.s2
    this.light = this.hueSemen > .5 ? opt.l1 : opt.l2
    this.maxSpeed = this.hueSemen > .5 ? 3 : 2
  }
  
  update() {
    this.follow()
    
    this.vx += this.ax
    this.vy += this.ay
    
    var p = Math.sqrt(this.vx * this.vx + this.vy * this.vy)
    var a = Math.atan2(this.vy, this.vx)
    var m = Math.min(this.maxSpeed, p)
    this.vx = Math.cos(a) * m
    this.vy = Math.sin(a) * m
    
    this.x += this.vx
    this.y += this.vy
    this.ax = 0
    this.ay = 0
    
    this.edges()
  }
  
  follow() {
    let angle = (noise(this.x * opt.noiseScale, this.y * opt.noiseScale, time * opt.noiseScale)) * Math.PI * 0.5 + opt.angle
    
    this.ax += Math.cos(angle)
    this.ay += Math.sin(angle)
    
  }
  
  updatePrev() {
    this.lx = this.x
    this.ly = this.y
  }
  
  edges() {
    if (this.x < 0) {
      this.x = width
      this.updatePrev()
    }
    if (this.x > width) {
      this.x = 0
      this.updatePrev()
    }
    if (this.y < 0) {
      this.y = height
      this.updatePrev()
    }
    if (this.y > height) {
      this.y = 0
      this.updatePrev()
    }
  }
  
  render () {
    stroke(`hsla(${this.hue}, ${this.sat}%, ${this.light}%, .5)`)
    line(this.x, this.y, this.lx, this.ly)
    this.updatePrev()
  }
}


/*--------------------
Setup
--------------------*/
function setup() {
  createCanvas(windowWidth, windowHeight)
  for (let i = 0; i < opt.particles; i++) {
    Particles.push(new Particle(Math.random() * width, Math.random() * height))
  }
  strokeWeight(opt.strokeWeight)
}


/*--------------------
Draw
--------------------*/
function draw() {
  time++
  background(0, 100 - opt.tail)
  
  for (let p of Particles) {
    p.update()
    p.render()
  }
}


/*--------------------
Resize
--------------------*/
function windowResized() {
  resizeCanvas(windowWidth, windowHeight)
}