<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8">
<meta name="viewport" content="width=device-width, initial-scale=1.0, maximum-scale=1.0, user-scalable=no">
<meta http-equiv="X-UA-Compatible" content="IE=Edge,chrome=1">
</head>
<body>
<canvas id="content" width="1250px" height="602px"></canvas>
</body>
</html>
<script>
var cav = document.getElementById('content');
var w = window.screen.width;
var h = window.screen.height;
var yPositions = Array(300).join(0).split('');
var ctx = cav.getContext('2d');
var draw = function(){
ctx.fillStyle = 'rgba(0,0,0,.05)';
ctx.fillRect(0,0,w,h);
ctx.fillStyle = 'green';
ctx.font = '20px';
yPositions.map(function(y,index){
text = String.fromCharCode(1e2+Math.random()*330);
x = index*10;
cav.getContext('2d').fillText(text,x,y);
if(y>Math.random()*1e4){
yPositions[index]=0;
}else{
yPositions[index]=y+10;
}
});
}
setInterval('draw()',30);
</script>