404!

var c = document.createElement('canvas');
var w = window.innerWidth / 4, h = window.innerHeight / 4;
c.width = w;
c.height = h;
var ctx = c.getContext('2d');
ctx.fillStyle = '#fff';
ctx.strokeStyle = '#005791';
ctx.lineWidth = 2;
function wave(t, n, f) {
    var val = 0;
    for (var k = 1; k < n; k ++) {
        val += Math.sin(Math.PI * 4 * ((2 * k) - 1) * f * t) / ((2 * k) - 1);
    }
    return (4 / Math.PI) * val;
}
function draw(n, f, a) {
  ctx.fillRect(0,0,w,h);
  ctx.beginPath();
  for (var t = 0; t < 1.05; t += 0.005) {
      var y = wave(t * Math.PI, n, f)
      ctx.lineTo(t * w * 1.26, (h/2) + (y * h/4));
  }
  ctx.stroke();
}
function drawAt(n) {
  draw(n, 0.2);
  document.body.style.backgroundImage = 'url(' + c.toDataURL(); ')';
  document.body.style.backgroundSize = '' + (w / 2) + 'px ' + (h / 2) + 'px';
}
document.onmousemove = function(e) {
  drawAt((Math.floor(e.pageX * 20 / window.innerWidth)) + 1);
}
drawAt(0.5);