I built this product slider as part of a wine shop I was working on in 2015, and since it's also featured in a case study here on my site, I had a couple of people asking me how the animation was done.

Well, it’s really quite simple – so here’s a quick rundown on how to make the bottles dance. You can see the actual live thing in action on one of the product pages here. Grab some Grüner Veltliner while you’re at it.

# The Slider

Markup is pretty straightforward, just your standard slider structure. A parent div and an ul with some list items. The real production version obviously has a little bit more going on, what with that fancy ratings popover and all. But for now, this should do the job:

<div class="slider">
  <ul class="slider__content">

    <li class="slider__item">
      <a href="link/to/product">
        <img src="image_of_bottle.jpg" alt="" />
      </a>
    </li>

    <li class="slider__item">...</li>
    <li class="slider__item">...</li>

  </ul>
</div>

To make this into a slider widget, you will need some CSS and a bit of Javascript. I used a jQuery plugin called Flexslider for this one, and I like it a lot. But almost any other slider would work too. The only important part for this effect is a callback function that gets triggered before each sliding transition.

Flexslider does exactly that with its before method. You pass it the $slider variable (the parent element), and then apply a class to it that later controls the animation state. After the animation has finished, we need to remove that class again. My wiggle lasts about a second, so I put in a setTimeout for that duration (plus a little more for good measure).

$slider.flexslider({
  //animation: 'slide',
  //selector: '.slider__item',
  //animationLoop: false,
  //slideshow: false,
  before: function($slider){
    $slider.addClass('slider--shaking');
    window.setTimeout(function(){
      $slider.removeClass('slider--shaking');
    }, 1200);
  }
});

# The Animation

Next up is the actual CSS keyframe animation that makes the bottles swing from side to side. Mine looks like this:

@keyframes wiggle {
  25%  { transform: rotate3d(0, 0, 1, 6deg)  }
  50%  { transform: rotate3d(0, 0, 1, -4deg) }
  75%  { transform: rotate3d(0, 0, 1, 2deg)  }
  100% { transform: rotate3d(0, 0, 1, 0deg)  }
}

We tilt the items first right, then left, then right again, losing momentum in each turn to simulate the inertia a real bottle would have.
The rotate3d is to force graphic acceleration, which makes for smoother animation performance. Also, be sure to include vendor prefixes for the transform - or, if you’re lazy like me, let Autoprefixr do that for you.

The last step is to apply the keyframe animation to your slider every time it gets triggered.
Two things are important here:

1. define the transform-origin for each object. This will be the fixed point that anchors the animation, it corresponds to the center of gravity in the real world. For my bottles, that would be center bottom.

2. 💡__PRO TIP:__ to make it seem more realistic, apply a little delay to every other bottle, so they dont all wiggle in unison. A small offset in timing does the trick.

.slider--shaking .slider__item {
  //disable hover effects while transitioning
  pointer-events:none;

  //set up the wiggle animation
  animation-name: wiggle;
  animation-duration: 1s;
  animation-fill-mode: both;

  //set the 'fixed point' of the animation
  transform-origin:bottom center;
}

.slider--shaking .slider__item:nth-child(2n) {
  //slightly offset every other item
  animation-delay:.1s;
}

Aaand you’re done! Not much to it, but makes for a nice touch and a cool thing to show off. 🍾