A Matrix rain effect

matrix.js

function _(tagname, attributes) {
    var result = null;
    if(attributes && attributes.xmlns) {
        result = document.createElementNS(attributes.xmlns, tagname);
    } else {
        result = document.createElement(tagname || "div");
    }
    if(attributes) {
        Object.keys(attributes).forEach(function(name) {
            if("xmlns" == name) return;
            var value = attributes[name];
            result.setAttribute(name, value);
        });
    }
    return result;
}
function startMatrix() {
    var chinese = (function() {
        var f=" 0123456789";
        for(var i=0;i<45;i++) {
            f+=String.fromCharCode(i+65393);
        }
        return f.split("");
    })();
    var c = _("canvas",{"width":window.innerWidth,
        "height":window.innerHeight,"style":(
            "position:fixed;top:0;left:0;z-index:-255;"
        )});
    var ctx = c.getContext("2d");
    var font_size = 10;
    var columns = c.width/font_size;
    var drops = [];
    for(var x=0; x<columns; x++) {
        drops[x] = 1; 
    }
    function draw() {
        ctx.fillStyle = "rgba(0, 0, 0, 0.05)";
        ctx.fillRect(0, 0, c.width, c.height);
        ctx.fillStyle = "#0F0";
        ctx.font = font_size + "px monospace";
        for(var i=0; i<drops.length; i++) {
            var text = chinese[Math.floor(Math.random()*chinese.length)];
            ctx.fillText(text, i*font_size, drops[i]*font_size);
            if(drops[i]*font_size > c.height && Math.random() > 0.975) {
                drops[i] = 0;
            }
            drops[i]++;
        }
    }
    document.body.appendChild(c);
    setInterval(draw,33);
}
startMatrix();