<canvas id="pizza"></canvas>

<!--

  Inspired by http://9gag.com/gag/aVePMd8
  But not quit there yet :)

-->
body {
  background: #6A1B9A;
  height: 100vh;
  margin: 0;
  display: flex;
  align-items: center;
  justify-content: center;
}
'use strict'

let toRadians = (deg) => deg * Math.PI / 180
let map = (val, a1, a2, b1, b2) => b1 + (val - a1) * (b2 - b1) / (a2 - a1)

class Pizza {
  constructor(id) {
    this.canvas = document.getElementById(id)
    this.ctx = this.canvas.getContext('2d')

    this.sliceCount = 6
    this.sliceSize = 80

    this.width = this.height = this.canvas.height = this.canvas.width = this.sliceSize * 2 + 50
    this.center = this.height / 2 | 0

    this.sliceDegree = 360 / this.sliceCount
    this.sliceRadians = toRadians(this.sliceDegree)
    this.progress = 0
    this.cooldown = 10

  }

  update() {
    let ctx = this.ctx
    ctx.clearRect(0, 0, this.width, this.height)

    if (--this.cooldown < 0) this.progress += this.sliceRadians*0.01 + this.progress * 0.07

    ctx.save()
    ctx.translate(this.center, this.center)
    
    for (let i = this.sliceCount - 1; i > 0; i--) {

      let rad
      if (i === this.sliceCount - 1) {
        let ii = this.sliceCount - 1

        rad = this.sliceRadians * i + this.progress

        ctx.strokeStyle = '#FBC02D'
        cheese(ctx, rad, .9, ii, this.sliceSize, this.sliceDegree)
        cheese(ctx, rad, .6, ii, this.sliceSize, this.sliceDegree)
        cheese(ctx, rad, .5, ii, this.sliceSize, this.sliceDegree)
        cheese(ctx, rad, .3, ii, this.sliceSize, this.sliceDegree)

      } else rad = this.sliceRadians * i
      
      // border
      ctx.beginPath()
      ctx.lineCap = 'butt'
      ctx.lineWidth = 11
      ctx.arc(0, 0, this.sliceSize, rad, rad + this.sliceRadians)
      ctx.strokeStyle = '#F57F17'
      ctx.stroke()

      // slice
      let startX = this.sliceSize * Math.cos(rad)
      let startY = this.sliceSize * Math.sin(rad)
      let endX = this.sliceSize * Math.cos(rad + this.sliceRadians)
      let endY = this.sliceSize * Math.sin(rad + this.sliceRadians)
      let varriation = [0.9,0.7,1.1,1.2]
      ctx.fillStyle = '#FBC02D'
      ctx.beginPath()
      ctx.moveTo(0, 0)
      ctx.lineTo(startX, startY)
      ctx.arc(0, 0, this.sliceSize, rad, rad + this.sliceRadians)
      ctx.lineTo(0, 0)
      ctx.closePath()
      ctx.fill()
      ctx.lineWidth = .3
      ctx.stroke()

      // meat
      let x = this.sliceSize * .65 * Math.cos(rad + this.sliceRadians / 2)
      let y = this.sliceSize * .65 * Math.sin(rad + this.sliceRadians / 2)
      ctx.beginPath()
      ctx.arc(x, y, this.sliceDegree / 6, 0, 2 * Math.PI)
      ctx.fillStyle = '#D84315'
      ctx.fill()

    }

    ctx.restore()

    if (this.progress > this.sliceRadians) {
      ctx.translate(this.center, this.center)
      ctx.rotate(-this.sliceDegree * Math.PI / 180)
      ctx.translate(-this.center, -this.center)

      this.progress = 0
      this.cooldown = 20
    }

  }

}

function cheese(ctx, rad, multi, ii, sliceSize, sliceDegree) {
  let x1 = sliceSize * multi * Math.cos(toRadians(ii * sliceDegree) - .2)
  let y1 = sliceSize * multi * Math.sin(toRadians(ii * sliceDegree) - .2)
  let x2 = sliceSize * multi * Math.cos(rad + .2)
  let y2 = sliceSize * multi * Math.sin(rad + .2)

  let csx = sliceSize * Math.cos(rad)
  let csy = sliceSize * Math.sin(rad)

  var d = Math.sqrt((x1 - csx) * (x1 - csx) + (y1 - csy) * (y1 - csy))
  ctx.beginPath()
  ctx.lineCap = 'round'

  let percentage = map(d, 15, 70, 1.2, 0.2)

  let tx = x1 + (x2 - x1) * percentage
  let ty = y1 + (y2 - y1) * percentage
  ctx.moveTo(x1, y1)
  ctx.lineTo(tx, ty)

  tx = x2 + (x1 - x2) * percentage
  ty = y2 + (y1 - y2) * percentage
  ctx.moveTo(x2, y2)
  ctx.lineTo(tx, ty)

  ctx.lineWidth = map(d, 0, 100, 20, 2)
  ctx.stroke()
}

let pizza = new Pizza('pizza')

;(function update() {
  requestAnimationFrame(update)
  pizza.update()

}())
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