Sliding puzzle

Just an [After Dark](https://en.wikipedia.org/wiki/After_Dark_(software)-style sliding puzzle.

<!DOCTYPE html>
<meta charset="utf-8">
<style>
  div {
    background: black url('neon.jpg');
    position: absolute;
    border: 0.5px solid black;
    box-sizing: border-box;
  }
</style>
<body>
<script src="//d3js.org/d3.v4.min.js"></script>
<script>

var rows = 10,
    columns = 16,
    size = 60,
    holeIndex = Math.floor(Math.random() * rows * columns),
    last;

var tiles = d3.select("body").selectAll("div")
  .data(d3.range(rows * columns))
  .enter()
  .append("div")
    .style("background-position", getPosition)
    .style("width", size + "px")
    .style("height", size + "px")
    .call(move)
    .nodes();

tiles[holeIndex].remove();
tiles[holeIndex] = null;

swap();

function swap(){

var destination = d3.shuffle(getNeighbors(holeIndex)).filter(function(d){
    return tiles[d] !== last;
  })[0];

last = tiles[destination];

tiles[destination] = null;

tiles[holeIndex] = last;

d3.select(last).datum(holeIndex)
    .transition()
    .duration(150)
    .call(move)
    .on("end", swap);

holeIndex = destination;

}

function getPosition(d){
  return "-" + getLeft(d) + " -" + getTop(d);
}

function getNeighbors(d){
  var neighbors = [];

var row = Math.floor(d / columns),
      column = d % columns;

if (row > 0) {
    neighbors.push(d - columns);
  }

if (row < rows - 1) {
    neighbors.push(d + columns);
  }

if (column > 0) {
    neighbors.push(d - 1);
  }

if (column < columns - 1) {
    neighbors.push(d + 1);
  }

return neighbors;
}

function move(sel) {

sel.style("top", getTop)
    .style("left", getLeft);

}

function getTop(d){
  return (Math.floor(d / columns) * size) + "px";
}

function getLeft(d){
  return (d % columns * size) + "px";
}

</script>

https://d3js.org/d3.v4.min.js