Rainbow background

<script>
 // Author: pahapoika91
 // Name: Rainbow Background
 // Description: The background changes colors like a rainbow, so kawaii!

 var tick = 0;
 var rate = 0.1;
 window.onload=function(){
  setInterval(function(){
   tick=tick + rate;
   var red = Math.sin(tick) * 127 + 128;
   var green = Math.sin(tick + 90) * 127 + 128;
   var blue = Math.sin(tick + 270) * 127 + 128;
   red=parseInt(red);
   green=parseInt(green);
   blue=parseInt(blue);
   document.body.style.backgroundColor="rgb("+red+","+green+","+blue+")";
  },50);
 };
</script>