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HTML

              
                
<div class="graduation_twinklers">
  <div id="twinkler_1" class="twinkler" aria-hidden="true"></div>
  <a class="graduation_twinklers_cta" href="https://www.york.ac.uk/students/studying/graduation/">
    <h1>Congratulations to today's graduates</h1>
    <p><strong>Watch ceremonies online and find out all you need to know for your big day</strong></p>
  </a>
	<div id="twinkler_2" class="twinkler" aria-hidden="true"></div>
</div>
              
            
!

CSS

              
                /* -------------------------------------------------- */

* { box-sizing: border-box; }

body
{
  margin: 0;
  background: #f0f0f0;
  font-family: chaparral-pro,"Times New Roman",Times,serif;
}

h1
{
  font-family: chaparral-pro,"Times New Roman",Times,serif;
  font-weight: 600;
}

/* -------------------------------------------------- */

.graduation_twinklers
{
  position: relative;
  
	background: #DA1A33 url( 'twinkler_bg_mobile.png' ) center / contain no-repeat;
	color: white;

	overflow: hidden;
	padding: 2rem calc( 50% - 40em );

	display: block;
	text-decoration: none;
	
	font-family: chaparral-pro,"Times New Roman",Times,serif;
	font-weight: normal;
}

@media screen and ( min-width:600px )
{
	.graduation_twinklers
	{
		background: #DA1A33 url( 'twinkler_bg.png' ) center right / contain no-repeat;
	}
}

.graduation_twinklers_cta
{
	display: block;
	margin: 1.5rem 1rem;

	text-align: center;

	color: inherit;
	text-decoration: none;
}

.graduation_twinklers_cta:hover
{
	color: inherit;
	text-decoration: none;
}

.graduation_twinklers_cta:hover p
{
	text-decoration: underline;
}

.graduation_twinklers_cta h1
{
	text-transform: uppercase;
	margin: 0;
}

.graduation_twinklers_cta p
{
	margin: 0;
}

/* Layers */

.twinkler_layer
{
	padding: 0 0.25rem;

	display: flex;
	flex-flow: row wrap;
	justify-content: space-around;
}

@media screen and ( min-width:700px ) { .twinkler_layer { padding: 0 1rem; } }

/* Stack all layers on top of the first */

.twinkler { position: relative; }

.twinkler_layer:not( :first-child )
{
	position: absolute;
	top: 0;
	left: 0;
	width: 100%;
	height: 100%;
}

/* The twinkling items */

.twinkler_layer > *
{
	height: 1.5em;
	line-height: 1.5em;
	
	flex-grow: 0;
	flex-shrink: 0;

	text-align: center;
	white-space: nowrap;
}

/* Font sizing */

.twinkler_layer > * { font-size: 0.7em; }

@media screen and ( min-width:400px ){ .twinkler_layer > * { font-size: 0.8em; } }
@media screen and ( min-width:600px ){ .twinkler_layer > * { font-size: 0.9em; } }
@media screen and ( min-width:900px ){ .twinkler_layer > * { font-size: 1em; } }

/* Transitions */

/* Default/dormant */
.twinkler_layer > *
{
	pointer-events: none;
	opacity: 0;

	transform: perspective( 100px ) rotateX( 90deg ) scale( 2 );
	transition: all 1000ms ease-out;
}

/* Active */
.twinkler_layer > *.is_twinkling
{
	pointer-events: auto;
	opacity: 1;
  
	transform: perspective( 100px );
	transition-delay: 250ms;
}

/* Fading out */
.twinkler_layer > *.is_fading
{
	pointer-events: none;
	opacity: 0;
  
	transform: perspective( 100px ) rotateX( -90deg ) scale( 2 );
	transition-timing-function: ease-in;
}

/*
.graduation_twinklers:hover .twinkler_layer > *
{
	opacity:1 !important;
	transform: none !important;
	outline: 1px solid cyan;
}
*/
              
            
!

JS

              
                
// --------------------------------------------------

var TWINKLER = function( $container , items )
{
	// Settings

  this.items_per_layer = 50;

	this.min_interval =  500; // ms
	this.max_interval = 1500; // ms

	// Storage

	this.items = items;
	this.$container = $container;

	this.layers = null;

	this.timer = null;

	this.slots = null;
	this.slot_cursor = null;

	// One-off initialisations

	this.sort_items_by_length();

	// Organise our layers
	this.layers = this.distribute_layers();
	
	// Build/refresh the DOM
	this.render();

	// Get ready...
	this.warm_up();

	// Go!
	this.cycle();
};

// --------------------------------------------------

TWINKLER.prototype.warm_up = function()
{
	// Setup

	var $layers = this.$container.querySelectorAll( ".twinkler_layer" );
	var items_per_layer = $layers[ 0 ].children.length;

	// Make an array of shuffled indexes, this is the order in which slots will be cycled

	var shuffled_index = [];
	for( var i = 1 ; i <= items_per_layer ; i ++ ) shuffled_index.push( i );

	var shuffle_cursor = items_per_layer;

	while( shuffle_cursor != 0 )
	{
		random_index = Math.floor( Math.random() * shuffle_cursor ); 
		shuffle_cursor--;

		var temp = shuffled_index[ shuffle_cursor ];
		shuffled_index[ shuffle_cursor ] = shuffled_index[ random_index ];
		shuffled_index[ random_index ] = temp;
	}

	// Make a big array of all the slots with their current index
	
	this.slots = [];

	for( var s = 0 ; s < shuffled_index.length ; s ++ )
	{
		var slot =
		{
			index: 0,
			$items: this.$container.querySelectorAll( ".twinkler_layer > *:nth-child("+parseInt( shuffled_index[ s ] )+")" ),
		};

		this.slots.push( slot );
	}

	// Reset the slot cursor

	this.slot_cursor = 0;
}

// --------------------------------------------------

TWINKLER.prototype.cycle = function()
{
	// Get the current slot deets
	var slot = this.slots[ this.slot_cursor ];

	// Get the current item index
	var item_index = slot.index;

	// Get the next item index, skipping empties
	var next_item_index = item_index;
	do { next_item_index = ( next_item_index + 1 ) % slot.$items.length; }
	while( slot.$items[ next_item_index ].innerHTML == '' )

	// Update the big old slots array
	slot.index = next_item_index;

	// Get a delay for the next transition
	var delay = parseInt( this.min_interval + Math.round( Math.random() * ( this.max_interval - this.min_interval ) ) );

	// Progress the slot cursor
	this.slot_cursor = ( this.slot_cursor + 1 ) % this.slots.length;

	this.timer = setTimeout( this.cycle.bind( this ) , delay );

	setTimeout( function(){
		slot.$items[ item_index ].classList.add( "is_fading" );
		slot.$items[ item_index ].classList.remove( "is_twinkling" );
		slot.$items[ next_item_index ].classList.add( "is_twinkling" );
	} , delay );

	setTimeout( function(){
		slot.$items[ item_index ].classList.remove( "is_fading" );
	} , parseInt( delay + 3000 ) );
}

// --------------------------------------------------

TWINKLER.prototype.render = function()
{
	var number_of_layers = this.layers.length;

	// Create somewhere to build the layers
	
	var $layers_staging = [];
	
	for( var l = 0 ; l < number_of_layers ; l ++ )
	{
		// Make the layer container
		var $layer = document.createElement( 'div' );
		$layer.classList.add( 'twinkler_layer' );
	
		$layers_staging.push( $layer );
	}
	
	// Create the items in each layer
	for( var i = 0 ; i < this.layers[ 0 ].length ; i ++ )
	{
		// Get the max length of the items at this index
		var max_length = 0;
		for( var l = 0 ; l < number_of_layers ; l ++ )
		{
			if( this.layers[ l ][ i ] ) max_length = Math.max( max_length , this.layers[ l ][ i ].length );
		}
	
		// Use the max length to calculate a width for these items
		var css_width = parseFloat( ( max_length * 0.7 ) + 0.1 ) + "em";
	
		// Create the item in each layer
		for( var l = 0 ; l < number_of_layers ; l ++ )
		{
			var $item = document.createElement( 'div' );
			$item.style.flexBasis = css_width;
			$item.innerHTML = this.layers[ l ][ i ];
	
			// Items in the first layer start visible
			if( l == 0 ) $item.classList.add( 'is_twinkling' );
	
			// Add to the staging area
			$layers_staging[ l ].appendChild( $item );
		}
	}
	
	// Empty our container first

	this.$container.innerHTML = '';

	// Add our layers to the DOM
	
	for( var l = 0 ; l < number_of_layers ; l ++ )
	{
		this.$container.appendChild( $layers_staging[ l ] );
	}

}

// --------------------------------------------------
// Sorts all items by name length

TWINKLER.prototype.sort_items_by_length = function()
{
	this.items.sort( function( a , b )
	{
		if( b.length == a.length )
		{
			return ( Math.random() * 2 ) - 1;
		}
		else return a.length - b.length;
	} );
}

// --------------------------------------------------
// Splits the one array into several layer arrays with synced item lengths

TWINKLER.prototype.distribute_layers = function()
{
	var number_of_layers = Math.ceil( this.items.length / this.items_per_layer );

	// Set up empty containers for our layers

	var layers = [];

	for( var l = 0 ; l < number_of_layers ; l ++ )
	{
		layers[ l ] = [];
	}

	// Distribute the items into their layers

	for( var i = 0 ; i < this.items.length ; i += number_of_layers )
	{
		for( var l = 0 ; l < number_of_layers ; l ++ )
		{
			layers[ l ].push( this.items[ i + l ] || "" );
		}
	}

	// Randomise the order of each layer

	var cursor = layers[ 0 ].length;

	while( cursor != 0 )
	{
		random_index = Math.floor( Math.random() * cursor ); 
		cursor--;

		// Swap items in each layer
		for( var l = 0 ; l < number_of_layers ; l ++ )
		{
			var swap = layers[ l ][ cursor ];
			layers[ l ][ cursor ] = layers[ l ][ random_index ];
			layers[ l ][ random_index ] = swap;
		}
	}

	return layers;
}

// --------------------------------------------------


		// --------------------------------------------------
		// Shuffle everything first
		
		var cursor = all_items.length;

		while( cursor != 0 )
		{
			random_index = Math.floor( Math.random() * cursor ); 
			cursor--;
			
			var temp = all_items[ cursor ];
			all_items[ cursor ] = all_items[ random_index ];
			all_items[ random_index ] = temp;
		}
		
		// --------------------------------------------------
		// Split into 2 arrays
		
		var midpoint = Math.ceil( all_items.length / 2 );
		
		var items_1 = all_items.slice( 0 , midpoint );
		var items_2 = all_items.slice( midpoint ) ;
		
		// --------------------------------------------------
		// Go!
		
		var twinkler_1 = new TWINKLER( document.getElementById( 'twinkler_1' ) , items_1 );
		var twinkler_2 = new TWINKLER( document.getElementById( 'twinkler_2' ) , items_2 );
		
		// --------------------------------------------------
              
            
!
999px

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