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Here you can Sed posuere consectetur est at lobortis. Donec ullamcorper nulla non metus auctor fringilla. Maecenas sed diam eget risus varius blandit sit amet non magna. Donec id elit non mi porta gravida at eget metus. Praesent commodo cursus magna, vel scelerisque nisl consectetur et.

              <!-- Original code here https://gist.github.com/twolfson/5b1a1ed21a77bc0fdd215e80ee7225cb -->
  p Click and drag a circle to see the our distance to segment update!
  svg#scene(width="400", height="400", viewBox="0 0 400 400", xmlns="https://www.w3.org/2000/svg")
    //- DEV: We put our line first so it's hidden behind our vertex z-indicies
    line#line--ab.line(x1="120", y1="170", x2="280", y2="170",
      stroke-width="10", stroke="#000")
    line#line--cx.line(x1="60", y1="260", x2="120", y2="170",
      stroke-width="5", stroke="#999", stroke-dasharray="5,5")
    circle#vertex--a.vertex(cx="120", cy="170", r="20")
    circle#vertex--b.vertex(cx="280", cy="170", r="20")
    circle#vertex--c.vertex(cx="60", cy="260", r="20")

              body {
  /* https://github.com/corysimmons/typographic/blob/2.9.3/scss/typographic.scss#L34 */
  font-family: 'Helvetica Neue', 'Helvetica', 'Arial', 'sans-serif';

/* Medium screenshot specific offsets, no height seems to be present */
@media screen and (width: 1024px) {
  .container {
    width: 768px; /* 1024 - 2*(8 - 120 - ~6) -- visual inspection of orange dot in Medium */
    margin: 0 auto;
    padding-top: 51px; /* 43px for Codepen text + 8px gutter width */

#scene {
  border: 1px solid #000;

.vertex {
  cursor: pointer;
  stroke: #000;
  stroke-width: 5px;

#vertex--a {
  fill: orange;
#vertex--b {
  fill: blue;
#vertex--c {
  fill: limegreen;
              const Draggabilly = window.Draggabilly;
document.addEventListener('DOMContentLoaded', function handleReady () {
  // Resolve our circle
  // TODO: Add assertion for element resolve
  let sceneEl = document.querySelector('#scene');
  let vertexAEl = sceneEl.querySelector('#vertex--a');
  let vertexBEl = sceneEl.querySelector('#vertex--b');
  let vertexCEl = sceneEl.querySelector('#vertex--c');
  let lineABEl = sceneEl.querySelector('#line--ab');
  let lineCXEl = sceneEl.querySelector('#line--cx');

  // Add our drag bindings
  function bindCircleDraggabilly(circleEl) {
    // Initialize our bindings
    let draggie = new Draggabilly(circleEl);

    // Update our bindings to support SVG
    // https://github.com/desandro/draggabilly/blob/v2.1.1/draggabilly.js#L266
    // https://github.com/desandro/draggabilly/blob/v2.1.1/draggabilly.js#L184-L194
    draggie._getPosition = function() {
      let x = parseFloat(this.element.getAttribute('cx'), 10);
      let y = parseFloat(this.element.getAttribute('cy'), 10);
      // Clean up 'auto' or other non-integer values
      this.position.x = isNaN(x) ? 0 : x;
      this.position.y = isNaN(y) ? 0 : y;
    // https://github.com/desandro/draggabilly/blob/v2.1.1/draggabilly.js#L424-L427
    draggie.positionDrag = function () {
      this.element.setAttribute('cx', this.startPosition.x + this.dragPoint.x);
      this.element.setAttribute('cy', this.startPosition.y + this.dragPoint.y);
    // https://github.com/desandro/draggabilly/blob/v2.1.1/draggabilly.js#L418-L422
    draggie.setLeftTop = function () {
      this.element.setAttribute('cx', this.position.x);
      this.element.setAttribute('cy', this.position.y);

    // Return our overridden binding
    return draggie;
  let vertexADraggie = bindCircleDraggabilly(vertexAEl);
  let vertexBDraggie = bindCircleDraggabilly(vertexBEl);
  let vertexCDraggie = bindCircleDraggabilly(vertexCEl);

  // Eagerly calculate our positions so we can have a shared redraw

  // When our vertices move, update our scene
  // DEV: We could be more intelligent about what updated but it's saner to perform a declarative render
  let aVertex = vec2.create();
  let bVertex = vec2.create();
  let cVertex = vec2.create();
  let abVector = vec2.create();
  let acVector = vec2.create();
  function updateScene() {
    // Update our lines
    lineABEl.setAttribute('x1', vertexADraggie.position.x);
    lineABEl.setAttribute('y1', vertexADraggie.position.y);
    lineABEl.setAttribute('x2', vertexBDraggie.position.x);
    lineABEl.setAttribute('y2', vertexBDraggie.position.y);
    lineCXEl.setAttribute('x1', vertexCDraggie.position.x);
    lineCXEl.setAttribute('y1', vertexCDraggie.position.y);

    // Unwrap our positions into vectors
    vec2.set(aVertex, vertexADraggie.position.x, vertexADraggie.position.y);
    vec2.set(bVertex, vertexBDraggie.position.x, vertexBDraggie.position.y);
    vec2.set(cVertex, vertexCDraggie.position.x, vertexCDraggie.position.y);

    // Perform our distance to segment calculations
    // Resolve the vectors between our vertices and our point
    // DEV: This overwrites our reusable variable values
    vec2.sub(abVector, bVertex, aVertex);
    vec2.sub(acVector, cVertex, aVertex);

    // Compare how much our vectors overlap
      3 scenarios (simplified to exclude multiple axises):
      * | are projections, \ | / are closest lines

      "Behind" A

      Between A and B

      "Ahead of" B
    // cos(θ) = percentage of AC that projects onto AB
    //   https://en.wikipedia.org/wiki/Dot_product#/media/File:Dot_Product.svg
    // cos(θ) * |AC|/|AB| = ratio for how much AC overlaps AB
    // acAbRatio = |AC|*|AB|*cos(θ) / |AB|^2 = |AC|*cos(θ)/|AB| = cos(θ) * |AC|/|AB|
    //   See deeper proof in https://gist.github.com/twolfson/207556d7ac0cd5d04fa283f6062841ab#finding-the-shortest-distance-from-a-point-to-asegment
    let baSquaredLength = vec2.squaredLength(abVector);
    let acAbRatio = vec2.dot(acVector, abVector) / baSquaredLength;

    // If our ratio/projection is "behind" AB, then update our line to point to A
    if (acAbRatio < 0.0) {
      lineCXEl.setAttribute('x2', vertexADraggie.position.x);
      lineCXEl.setAttribute('y2', vertexADraggie.position.y);
    // Otherwise, if our ratio/projection is "ahead of" AB, then update our line to point to B
    } else if (acAbRatio > 1.0) {
      lineCXEl.setAttribute('x2', vertexBDraggie.position.x);
      lineCXEl.setAttribute('y2', vertexBDraggie.position.y);
    // Otherwise (we're projecting between A and B), perform vector addition to find our projection
    } else {
      let cxX = aVertex[0] + acAbRatio * abVector[0];
      let cxY = aVertex[1] + acAbRatio * abVector[1];
      lineCXEl.setAttribute('x2', cxX);
      lineCXEl.setAttribute('y2', cxY);
  vertexADraggie.on('dragMove', updateScene);
  vertexBDraggie.on('dragMove', updateScene);
  vertexCDraggie.on('dragMove', updateScene);

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