Pen Settings

HTML

CSS

CSS Base

Vendor Prefixing

Add External Stylesheets/Pens

Any URL's added here will be added as <link>s in order, and before the CSS in the editor. If you link to another Pen, it will include the CSS from that Pen. If the preprocessor matches, it will attempt to combine them before processing.

+ add another resource

JavaScript

Babel is required to process package imports. If you need a different preprocessor remove all packages first.

Add External Scripts/Pens

Any URL's added here will be added as <script>s in order, and run before the JavaScript in the editor. You can use the URL of any other Pen and it will include the JavaScript from that Pen.

+ add another resource

Behavior

Save Automatically?

If active, Pens will autosave every 30 seconds after being saved once.

Auto-Updating Preview

If enabled, the preview panel updates automatically as you code. If disabled, use the "Run" button to update.

Format on Save

If enabled, your code will be formatted when you actively save your Pen. Note: your code becomes un-folded during formatting.

Editor Settings

Code Indentation

Want to change your Syntax Highlighting theme, Fonts and more?

Visit your global Editor Settings.

HTML

              
                
#help
  label(name='stiffness') Stifness: 
    b 30
  input(type='range' name='stiffness' min='0' max='100' step='0.1' value='30')
  p Stiffness of the spring. Higher values will create more sudden movement.

  label(name='damping') Damping: 
    b 1.5
  input(type='range' name='damping' min='0' max='5' step='0.1' value='1.5')
  p Damping, strength of opposing force. If set to 0, spring will oscillate indefinitely.
  
  label(name='mass') Mass: 
    b 0.1
  input(type='range' name='mass' min='0' max='0.5' step='0.001' value='0.1')
  p Mass of the moving object. Higher values will result in more lethargic movement.
  
  label(name='duration') Duration: 
    b 0ms

#circles
  .circle
  .circle
              
            
!

CSS

              
                *
  color: inherit
  font-size: inherit

body
  background: #1d1e22
  font-family: monospace
  padding: 50px
  color: #c6c8d4
  font-size: 1.2rem

#help
  max-width: 600px
  margin: 0 auto
  
  input
    width: 100%

  p
    margin-top: 0
    margin-bottom: 25px
    color: #63686f
    font-size: 0.8em

#circles
  max-width: 600px
  margin: 50px auto 50px
  display: flex
  flex-flow: row nowrap
  justify-content: space-around
  
  .circle
    width: 200px
    height: 200px
    border-radius: 100px
    z-index: 9999
    margin: 0 10px
    
    &:nth-child(1)
      left: calc(50% - 120px)
      background: radial-gradient(circle at 33% 33%, #5cabff, #000)
    
    &:nth-child(2)
      left: calc(50% + 120px)
      background: radial-gradient(circle at 33% 33%, #fb335c, #000)
              
            
!

JS

              
                const SpringSystem = ( () => {

  class Spring {

    constructor( system, id, options = {} ) {

      options = Object.assign( {
        config: {},
        rest: {},
        onUpdate: ( () => {} ),
        onComplete: ( () => {} ),
      }, options );

      this._config = Object.assign( {
        stiffness: 30,
        damping: 1.5,
        mass: 0.1,
      }, options.config );

      this._rest = Object.assign( {
        delta: 0.001,
        velocity: 0.01,
      }, options.rest );

      this._onUpdate = options.onUpdate;
      this._onComplete = options.onComplete;

      this._system = system;
      this._id = id;
      this._active = false;

      this._position = 0;
      this._target = 0;
      this._velocity = 0;

      this._update = this._update.bind( this );

    }

    _update( delta ) {

      delta /= 1000;

      const spring = ( this._position - this._target ) * -this._config.stiffness;
      const damper = this._velocity * -this._config.damping;
      const accelaration = ( spring + damper ) / this._config.mass;

      this._velocity += accelaration * delta;
      this._position += this._velocity * delta;

      this._onUpdate( this._position );

      const positionThreshold = this._round( this._position, this._rest.delta ) == this._target;
      const velocityThreshold = this._round( this._velocity, this._rest.velocity ) == 0;

      if ( positionThreshold && velocityThreshold ) {

        this._position = this._target;

        this._stop();
        this._onUpdate( this._position );
        this._onComplete( this._position );

      }

    }

    _round( value, precision ) {

      return Math.round( value / precision ) * precision;

    }

    _start() {

      this._system._addSpring( this );

      return this;

    }

    _stop() {

      this._system._removeSpring( this );

      return this;

    }

    setConfig( config = {} ) {

      this._config = Object.assign( this._config, config );

      return this;

    }

    setRest( rest = {} ) {

      this._rest = Object.assign( this._rest, rest );

      return this;

    }

    setPosition( v ) {

      this._position = v;
      this._start();

      return this;

    }

    setTarget( v ) {

      this._target = v;
      this._start();

      return this;

    }

    setAtRest() {

      this._stop();

      return this;

    }

    onUpdate( callback ) {

      this._onUpdate = callback;

      return this;

    }

    onComplete( callback ) {

      this._onComplete = callback;

      return this;

    }

    isActive() {

      return this._active;

    }

  }

  class SpringSystem {

    constructor() {

      this._uniq = 0;
      this._ids = [];
      this._springs = {};
      this._update = this._update.bind( this );
      this._raf = 0;
      this._time = 0;

    }

    _update() {

      const now = performance.now();
      const delta = now - this._time
      this._time = now;

      let i = this._ids.length;

      this._raf = i ? requestAnimationFrame( this._update ) : 0;

      while ( i-- )
        this._springs[ this._ids[ i ] ] && this._springs[ this._ids[ i ] ]._update( delta );

    }

    _addSpring( spring ) {

      if ( this._ids.indexOf( spring._id ) < 0 ) {

        this._ids.push( spring._id );
        this._springs[ spring._id ] = spring;
        spring._active = true;

      }

      if ( this._raf !== 0 ) return;

      this._time = performance.now();
      this._raf = requestAnimationFrame( this._update );

    }

    _removeSpring( spring ) {

      const index = this._ids.indexOf( spring._id );

      if ( index < 0 ) return;

      this._ids.splice( index, 1 );
      delete this._springs[ spring._id ];
      spring._active = false;
      spring = null;

    }

    createSpring( options = {} ) {

      const spring = new Spring( this, this._uniq++, options );

      return spring;

    }

  }

  return SpringSystem;

} )();

/*
██████  ███████ ███    ███  ██████  
██   ██ ██      ████  ████ ██    ██ 
██   ██ █████   ██ ████ ██ ██    ██ 
██   ██ ██      ██  ██  ██ ██    ██ 
██████  ███████ ██      ██  ██████  
*/

let start;

const system = new SpringSystem()
const springs = [];

const durationLabel = document.querySelector( 'label[name="duration"] b' );
const circles = document.querySelectorAll( '.circle' );

circles.forEach( circle => {

  const spring = system.createSpring( {
    onUpdate: position => {

      circle.style.transform = `scale(${ 1 - position / 5 })`;

    },
    onComplete: () => {

      const duration = Date.now() - start;
      if ( duration > 50 ) durationLabel.innerHTML = `${duration}ms`;

    },
  } );

  springs.push( spring );

  circle.addEventListener( 'mousedown', e => {

    start = Date.now();
    spring.setTarget( 1 )

  }, false );

} );

document.onmouseup = event => {

  start = Date.now();

  springs.forEach( spring => spring.setTarget( 0 ) );

};

const setupRange = name => {

  const label = document.querySelector( `label[name="${name}"] b` );
  const input = document.querySelector( `input[name="${name}"]` );

  input.oninput = () => {

    label.innerHTML = input.value;

    springs.forEach( spring => spring._config[ name ] = input.value );

  }

}

setupRange( 'stiffness' );
setupRange( 'damping' );
setupRange( 'mass' );
              
            
!
999px

Console