const is_iphone = (navigator.userAgent.match(/iPhone/i)) || (navigator.userAgent.match(/iPod/i))
const is_ipad = (navigator.userAgent.match(/iPad/i))
const is_android = (navigator.userAgent.match(/Android/i))
const is_mobile = is_iphone || is_ipad || is_android
const is_desktop = !is_mobile;
document.body.parentNode.classList.add(is_desktop ? 'desktop' : 'mobile')

function avg(a,b,n){ return (a*(n-1) + b)/n }
function rand(n){ return Math.random()*n }
function randint(n) { return ~~(Math.random()*n) }
function randrange(a,b){ return a+rand(b-a) }
function choice(a) { return a[randint(a.length)] }
function clamp(n,a,b) { return a > n ? a : n > b ? b : n }
function sign(n){ return n < 0 ? -1 : 1 }
function mod(n,m){ return n-(m * Math.floor(n/m)) }
function lerp(n,a,b){ return (b-a)*n+a }
function quantize(m,n){ return n * ((m/n)|0) }

function randgauss (obj, jog) {
  var radius = Math.random() * jog
  var angle = Math.random() * Math.PI * 2
  obj.left += Math.sin(angle) * radius
  obj.top += Math.cos(angle) * radius
}

function shuffle(a){
  for (var i = a.length; i > 0; i--){
    var r = randint(i)
    var swap = a[i-1]
    a[i-1] = a[r]
    a[r] = swap
  }
  return a
}

function toArray (els){
  return Array.prototype.slice.apply(els)
}

// easing functions
function circular (t) { return Math.sqrt( 1 - ( --t * t ) ) }
function quadratic (t) { return t * ( 2 - t ) }
function back (t) {
  var b = 4;
  return ( t = t - 1 ) * t * ( ( b + 1 ) * t + b ) + 1;
}
function bounce (t) {
  if (t >= 1) return 1;
  if ( ( t /= 1 ) < ( 1 / 2.75 ) ) {
    return 7.5625 * t * t;
  } else if ( t < ( 2 / 2.75 ) ) {
    return 7.5625 * ( t -= ( 1.5 / 2.75 ) ) * t + 0.75;
  } else if ( t < ( 2.5 / 2.75 ) ) {
    return 7.5625 * ( t -= ( 2.25 / 2.75 ) ) * t + 0.9375;
  } else {
    return 7.5625 * ( t -= ( 2.625 / 2.75 ) ) * t + 0.984375;
  }
}
function elastic (t) {
  var f = 0.22,
      e = 0.4;

  if ( t === 0 ) { return 0; }
  if ( t == 1 ) { return 1; }

  return ( e * Math.pow( 2, - 10 * t ) * Math.sin( ( t - f / 4 ) * ( 2 * Math.PI ) / f ) + 1 );
}

function preload (url) {
  var img = new Image ()
  var loaded = false, _cb
  img.onload = function(){
    if (loaded) return
    loaded = true
    if (_cb) { _cb(img) }
  }
  img.src = url
  if (img.complete) { img.onload() }
  return {
    then: function(cb){
      if (loaded) { cb(img) }
      else { _cb = cb }
    }
  }
}

function preloadImages () {
  var images = toArray(document.getElementById("images").children)
  var count = 0, ready = false, _cb
  images.forEach(function(img){
    var loaded = false
    img.onload = function(){
      if (loaded) return
      loaded = true
      done(img)
    }
    if (img.complete) { img.onload() }
  })
  function done () {
    if (++count == images.length && ! ready) {
      ready = true
      _cb && _cb()
    }
  }
  return {
    then: function(cb){
      if (ready) { cb() }
      else { _cb = cb }
    }
  }
}

function smoothstep(min,max,n){
  var t = clamp((n - min) / (max - min), 0.0, 1.0);
  return t * t * (3.0 - 2.0 * t)
}

function detrand (x,y) {
  return (Math.sin( x * 12.9898 + y * 78.233 ) * 43758.5453) % 1
}

function gray_to_transparency(img) {
  var canvas = document.createElement("canvas")
  var ctx = canvas.getContext('2d')
  var nw = img.naturalWidth, nh = img.naturalHeight
  canvas.width = nw
  canvas.height = nh
  ctx.drawImage(img,0,0)
  var pixels = ctx.getImageData(0,0,nw,nh)
  var data = pixels.data
  for (var i = 0, len = nw*nh*4; i < len; i += 4) {
    data[i+3] = data[i]
    data[i] = data[i+1] = data[i+2] = 255
  }
  ctx.putImageData(pixels,0,0)
  return canvas
}

var TWO_PI = 2*Math.PI