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                <div id="app"></div>


                * {
  box-sizing: border-box;

body {
  padding: 30px;
  font-family: 'Helvetica';
  background: #cad1d6;
  height: 500px;

// Tabs
.tab-set {
  padding: 20px;
  border: 1px solid #a5acb1;
  border-radius: 5px;
  background: #fff;

.tab-list {
  display: flex;
  position: relative;
  height: 100%;

.tab-list-item {
  flex: 1;
  padding: 12px;
  text-align: center;
  cursor: pointer;
  opacity: 0.5;
  transition: opacity 180ms ease-out;
  height: 100%;
  outline: 0; // add focus state for better accessibility
  border: 1px solid #a5acb1;
  &.is-active {
    opacity: 1;
    background: #999;


                const { Component, Children, PropTypes } = React
const { Motion, spring } = ReactMotion
const { AriaManager, AriaToggle, AriaPopover, AriaTabList, AriaTab, AriaPanel, AriaItem } = ReactARIA

const fastSpring = { stiffness: 400, damping: 40 }

class Tabs extends Component {
  constructor(props) {
    this.state = {
      tabs: [{
        id: 't1',
        title: <strong>What is a 529?</strong>,
        panel: <div><p>A 529 is a tax-advantaged investment 
            vehicle in the US designed for encouraging saving for 
            the future higher education expenses of a designated 
            beneficiary. You can use a 529 to pay for K-12 public, private and religios school tuition, post-secondary education costs, such as tuition, fees, books, supplies & equipment, room and board.</p></div>
      }, {
        id: 't2',
        title: <strong>Why use a 529?</strong>,
        panel: <div><p>>With the Economic Growth & Tax Relief Reconciliation Act of 2001, qualified distributions from 529 plans are exempt from federal income tax. </p></div>
      }, {
        id: 't3',
        title: <strong>Concerns about a 529?</strong>,
        panel: <div><ul>
              <li>If the money is not spent on education, expenses are subject to income tax, 
              plus a 10% penalty.</li>
              <li>Paying qualified expenses directly from a 529 may reduce a student's 
              eligibility for need based financial aid.</li>
              <li>Paying qualified expenses from a 529 may reduce eligibility for the 
              American Opportunities Tax Credit, due to IRS coordination restrictions.</li>
      activeId: 't1',
      height: 'auto'
    this._handleChange = this._handleChange.bind(this)

  _handleChange(activeId) {
    this.setState({ activeId })

  render() {
    const { tabs, activeId, height } = this.state
    const activeIndex = tabs.indexOf(tabs.filter(tab => === activeId)[0])
    return (
        <div className="tab-set">
            { dimensions =>
                style={{ x: spring(dimensions.width/3 * activeIndex, fastSpring) }}
              { value =>
                <AriaTabList className="tab-list">
                  {{ id, title }) =>
                      isActive={id === activeId}
                      {(props, isActive) => (
                        <div {...props} className={`tab-list-item ${isActive ? 'is-active' : ''}`}>
                      width: dimensions.width/3,
                      height: 2,
                      background: '#a5acb1',
                      position: 'absolute',
                      bottom: 0,
                      left: 0,
                      transform: `translate3d(${value.x}px, 0, 0)`
          <div className="tab-panels">
              style={{ overflow: 'hidden' }}
                {{ id, panel }) =>
                    isActive={id === activeId}

ReactDOM.render(<Tabs/>, document.getElementById('app'))