 <c span="row">row</c>
    <c span="8">8</c>

    <c span="invalid">invalid</c>
    <c span="9-3">9-3 (invalid)</c>

  </grid>

<pre id="css-output"></pre>
<script src="res/generate-grid.js"></script>
<script>
let css = Raster.generateCSS({
  minColumns: 1,
  maxColumns: 8,
  defaultColumns: 4,
})

let style = document.createElement('style')
document.head.appendChild(style)
style.appendChild(document.createTextNode(css))

let outel = document.querySelector('#css-output')
outel.appendChild(document.createTex