code-rain.js

var matrix = document.getElementById("matrix");
var ctx = matrix.getContext("2d");

matrix.height = window.innerHeight;
matrix.width = window.innerWidth;

var america = "ROCHESTERNATIONALTECHNICALINSTITUTEOFTECHNOLOGY20092011";
america = america.split("");

var font_size = 21;
var columns = matrix.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, matrix.width, matrix.height);
    ctx.fillStyle = "#0F0"; 
    ctx.font = "bold " + font_size + "px Courier";
    for(var i = 0; i < drops.length; i++) {
        var text = america[Math.floor(Math.random()*america.length)];
        ctx.fillText(text, i*font_size, drops[i]*font_size);
        if(drops[i]*font_size > matrix.height && Math.random() > 0.975)
            drops[i] = 0;
        drops[i]++; 
    }
}

setInterval(draw, 50);