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HTML

              
                <div class=snow>
  <i class=snow_flake></i>
  <i class=snow_flake></i>
  <i class=snow_flake></i>
  <i class=snow_flake-600px></i>
  <i class=snow_flake-600px></i>
  <i class=snow_flake-600px></i>
  <i class=snow_flake-600px></i>
  <i class=snow_flake-768px></i>
  <i class=snow_flake-768px></i>
  <i class=snow_flake-1024px></i>
  <i class=snow_flake-1024px></i>
  <i class=snow_flake-1024px></i>
  <i class=snow_flake-1280px></i>
  <i class=snow_flake-1280px></i>
  <i class=snow_flake-1366px></i>
  <i class=snow_flake-1600px></i>
  <i class=snow_flake-1600px></i>
  <i class=snow_flake-1800px></i>
  <i class=snow_flake-1800px></i>
  <i class=snow_flake-1920px></i>
  <i class=snow_flake-1920px></i>
</div>

<main>

  <header>
    <h1>CSS only Snowflakes</h1>
    <p>Originally written 15th November 2015 for Tesco.com.</p>
    <p>Please note the snowflake SVG remains the copyright of Tesco PLC.</p>
    <p>The full <a target=_blank title="[new window]" href="http://websemantics.uk/articles/snow/">Snowflakes article</a> (not updated).</p>
  </header>

  <div class=tall-content></div>
  <div class=tall-content></div>

</main>


<!-- Footer codepen include -->
[[[https://codepen.io/2kool2/pen/mKeeGM]]]
              
            
!

CSS

              
                /* Generic styling */

html{font-family: sans-serif; box-sizing: border-box}
*,:after,:before{box-sizing: inherit}
body,button{text-rendering: optimizeLegibility}
body{background-color: #ddd; color: #3a2c49; margin:0}
h1{color: #4B3D5A; font-weight:100; font-size: 2rem; margin: .618rem 0}
a{background: transparent; color: #236ECE; text-decoration: none}
a:hover,a:focus,a:active{color: #014cac}
p a:hover,a:focus,li a:hover,a:focus{text-decoration: underline; outline: 0}
header,
.tall-content{background-color: rgba(35,110,206,.15)}
header{padding: 4.236rem}
.tall-content{height: 50vh; margin: 50vh 0}




/* Snow place to be on a cold day in Tesco */

.snow {
  position: fixed;
  top: 0;
  left: 0;
  width: 100%;
  text-align: center;
  z-index: -1;

  /* Encourage hardware acceleration */
  /* 20vh per row of flakes - adjust falling animation too  */
  transform: translate3d(0, -20vh, 0);

  /* Flex used to space the i tags evenly horizontally. Plays nicely at inbetween widths */
  /* Temporarily disable if you are adjusting the number of flakes on screen */
  display:flex;
  justify-content: space-between;

  /* Allow for multi row snowflakes */
  flex-wrap: wrap;
}



    /* Generic styling of snowflakes, default animation and transform */

[class^="snow_flake"] {
  will-change: transform;
  display: inline-block;
  transform: translate3d(0, 0, 0);
  backface-visibility: hidden;
  perspective: 1000;
  animation: falling;
  animation-iteration-count: infinite;
 
  /* Filter is completely optional and may cause performance issues on low powered GPUs. */
  /* filter: drop-shadow(0 1px 1px rgba(0,0,0,.125)) blur(1px); */

  background-size: contain;
  background-repeat: no-repeat;
  backface-visibility: hidden;

/* Snowflake image remains the copyright of Tesco PLC. */
  background-image: url("data:image/svg+xml;charset=utf8,%3Csvg xmlns='http://www.w3.org/2000/svg' viewBox='0 0 96 96' fill='%23fff' fill-rule='evenodd'%3E%3Cpath d='M38.2 65l1-9.7 6.8-3.8v7.8L38.2 65zM58 65l-8-5.8v-7.8l6.8 4 1 9.6zm9.8-17l-9 3.8-6.6-3.8 7-4 8.6 4zm-39.4 0l8.7-4 7 4-6.5 3.8-8.8-4zM58 31l-1 9.6-7 4v-8l8-5.7zm-19.8 0l7.8 5.5v8l-6.7-3.8-1-9.8zm12-17L60.5 3.5l2.8 3-13.3 13v12L63 22l-1.7 16 10.2-5.7 5-18.3 4 1-4 14.4 12.2-7 2 3.6-12 7L93 37l-1.3 3.8-18.2-5-10.2 5.8L78 48l-14.7 6.4 10 5.6 18-5 1.2 4-14.3 3.8L90.6 70l-2 3.5L76 66.3l4 14.4-4 1-5-18.2-9.8-5.6L63 73.3 50 64v11.6L63.3 89l-2.8 3L50 81.5V96h-4V81.5L35.4 92l-2.8-3L46 75.8V64.4l-12.8 9.3 1.7-16-10.5 6-5 18-4-1 4-14.3-12.5 7L5 70l13-7.2-14.5-4 1-3.8L23 60l10-5.7L18.3 48l14.4-6.4-10.2-6-18.3 5-1-3.8 14.3-4-12.2-7 2-3.4 12.2 7-4-14.4 4-1 5 18.2 10.4 6-2-16 13 9.2V19.8L32.4 6.3l3-2.8L46 14V0h4v14z'/%3E%3C/svg%3E");
}


/* Four sizes, each requires individual origins set */

[class^="snow_flake"]:nth-child(4n+0) {
  width: 8rem;
  height: 8rem;
  transform-origin: -5% -5%;
}
[class^="snow_flake"]:nth-child(4n+1) {
  width: 6rem;
  height: 6rem;
  transform-origin: 15% 0;
}
[class^="snow_flake"]:nth-child(4n+2) {
  width: 4rem;
  height: 4rem;
  transform-origin: 0 -30%;
}
[class^="snow_flake"]:nth-child(4n+3) {
  width: 2rem;
  height: 2rem;
  transform-origin: -100% -100%;
}


/* Keep first snowflake close to the edge */

[class^="snow_flake"]:first-child {
  transform-origin: 60% 40%;
}


/* Delay the start times */

[class^="snow_flake"]:nth-of-type(5n+0) {
  animation-delay: 0s;
}
[class^="snow_flake"]:nth-of-type(5n+1) {
  animation-delay: 2s;
}
[class^="snow_flake"]:nth-of-type(5n+2) {
  animation-delay: 4s;
}
[class^="snow_flake"]:nth-of-type(5n+3) {
  animation-delay: 6s;
}
[class^="snow_flake"]:nth-of-type(5n+4) {
  animation-delay: 8s;
}


/* Animation durations are calculated to be multiples of each other +/- a few seconds for initial delays */

[class^="snow_flake"]:nth-child(3n+0) {
  animation-duration: 12s;
}
[class^="snow_flake"]:nth-child(3n+1) {
  animation-duration: 18s;
}
[class^="snow_flake"]:nth-child(3n+2) {
  animation-duration: 24s;
}


/* Tweak timing functions - a tad more random */

[class^="snow_flake"]:nth-of-type(6n+0) {
  animation-timing-function: ease-in-out;
}
[class^="snow_flake"]:nth-of-type(6n+1) {
  animation-timing-function: ease-out;
}
[class^="snow_flake"]:nth-of-type(6n+2) {
  animation-timing-function: ease;
}
[class^="snow_flake"]:nth-of-type(6n+3) {
  animation-timing-function: ease-in;
}
[class^="snow_flake"]:nth-of-type(6n+4) {
  animation-timing-function: linear;
}
[class^="snow_flake"]:nth-of-type(6n+5) {
  animation-timing-function: cubic-bezier(0.2, 0.3, 0.8, 0.9);
}


/* Tweak opacity - more randomness */

[class^="snow_flake"]:nth-of-type(7n+0) {opacity: 0.6;}
[class^="snow_flake"]:nth-of-type(7n+1) {opacity: 0.9;}
[class^="snow_flake"]:nth-of-type(7n+2) {opacity: 0.5;}
[class^="snow_flake"]:nth-of-type(7n+4) {opacity: 0.8;}
[class^="snow_flake"]:nth-of-type(7n+6) {opacity: 0.7;}


/* Filter is completely optional, and it may cause performance issues on low powered GPUs. */

[class^="snow_flake"]:nth-of-type(3n+0) {
  filter: drop-shadow(0 1px 1px rgba(0,0,0,.125));
}
[class^="snow_flake"]:nth-of-type(3n+1) {
  filter: blur(1px);
}


/* Increase number of snowflakes at common device widths */

.snow_flake-600px,
.snow_flake-768px,
.snow_flake-1024px,
.snow_flake-1280px,
.snow_flake-1366px,
.snow_flake-1440px,
.snow_flake-1600px,
.snow_flake-1800px,
.snow_flake-1920px {
  display: none;
}

@media (min-width: 600px) {
  .snow_flake-600px {
    display: inline-block;
  }
}

@media (min-width: 768px) {
  .snow_flake-768px {
    display: inline-block;
  }
}

@media (min-width: 1024px) {
  .snow_flake-1024px {
    display: inline-block;
  }
}

@media (min-width: 1280px) {
  .snow_flake-1280px {
    display: inline-block;
  }
}

@media (min-width: 1366px) {
  .snow_flake-1366px {
    display: inline-block;
  }
}

@media (min-width: 1600px) {
  .snow_flake-1600px {
    display: inline-block;
  }
}

@media (min-width: 1800px) {
  .snow_flake-1800px {
    display: inline-block;
  }
}

@media (min-width: 1920px) {
  .snow_flake-1920px {
    display: inline-block;
  }
}



/* Animation for all snowflakes */

@keyframes falling {
  from {
    transform: translate(0, 0) rotate(0deg) scale(0.8);
  }
  to {
    transform: translate(0, 120vh) rotate(360deg) scale(1.2);
  }
}
              
            
!

JS

              
                // JS is NOT a requirement!


var supportsES6 = function() {
  // https://gist.github.com/bendc/d7f3dbc83d0f65ca0433caf90378cd95
  try {
    new Function("(a = 0) => a");
    return true;
  }
  catch (err) {
    return false;
  }
}();



// Let it snow

// I wanted to delay placing the snowflakes into the HTML until after the page loaded. Which you use is up to you.

var Snow = (function (window, document) {
  
  return; // Delete this line, and the existing snow div, to let the JS embed the HTML content instead.

  'use strict';
  if (!supportsES6) return false;
  
  // Dynamically add snowflakes HTML to the page after page-load.

  function letItSnow() {
    const snowDiv = document.createElement('div');
    snowDiv.className = 'snow';
    snowDiv.innerHTML =  `
      <i class=snow_flake></i>
      <i class=snow_flake></i>
      <i class=snow_flake></i>
      <i class=snow_flake-600px></i>
      <i class=snow_flake-600px></i>
      <i class=snow_flake-600px></i>
      <i class=snow_flake-600px></i>
      <i class=snow_flake-768px></i>
      <i class=snow_flake-768px></i>
      <i class=snow_flake-1024px></i>
      <i class=snow_flake-1024px></i>
      <i class=snow_flake-1024px></i>
      <i class=snow_flake-1280px></i>
      <i class=snow_flake-1280px></i>
      <i class=snow_flake-1366px></i>
      <i class=snow_flake-1600px></i>
      <i class=snow_flake-1600px></i>
      <i class=snow_flake-1800px></i>
      <i class=snow_flake-1800px></i>
      <i class=snow_flake-1920px></i>
      <i class=snow_flake-1920px></i>`;

    document.body.insertBefore(snowDiv, document.body.childNodes[0]);
    
  };
  
  window.addEventListener('load', letItSnow, false);

}(window, document));


              
            
!
999px

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