ViewStack({
  paths: Object,
  store: Function
})

{
  // name of layer
  screens: {
   // WARN: root route '/' must be defined
   '/': callback=> {callback(html`<h1>A</h1>`)},
   // path : function that returns an HTML Element to a callback
   '/a': callback=> {callback(html`<h1>A</h1>`)}
  },
  sheets: {
   '/b': callback=> {callback(html`<h1>B</h1>`)}
  },
  modals: {
   '/c': callback=> {callback(html`<h1>C</h1>`)}
  }
}

var render = require('view-stack')({
  paths: {
    // name of layer
    screens: {
     // WARN: root route '/' must be defined
     '/': callback=> {callback(html`<h1>A</h1>`)},
     // path : function that returns an HTML Element to a callback
     '/a': callback=> {callback(html`<h1>A</h1>`)}
    },
    sheets: {
     '/b': callback=> {callback(html`<h1>B</h1>`)}
    },
    modals: {
     '/c': callback=> {callback(html`<h1>C</h1>`)}
    }
  },
  store: { title: 'Yippee!' }
})

document.body.appendChild(render())
// Initial view will be component `A`
// data passed to components will have a navigate method appended.
// data.navigate('/b') proceeds to next route.

// Static render a path
document.body.appendChild(render('/c'))