var snowmax = 35;
var snowcolor = ["#AAAACC","#DDDDFF","#CCCCDD","#F3F3F3","#F0FFFF","#FFFFFF","#EFF5FF"];
var snowtype = ["Arial Black","Arial Narrow","Times","Comic Sans MS"];
var snowletter = "*";
var sinkspeed = 0.6; 
var snowmaxsize = 40;
var snowminsize = 8;
var snowingzone = 1;

var snow = [];
var timer;
var x_mv = [];
var crds = [];
var lftrght = [];
var browserinfos = navigator.userAgent;
var ie5 = document.all && document.getElementById && !browserinfos.match(/Opera/);
var ns6 = document.getElementById && !document.all;
var opera = browserinfos.match(/Opera/);
var browserok = ie5 || ns6 || opera;

function randommaker(range) {
    return Math.floor(range * Math.random());
}

function initsnow() {
    var marginbottom = Math.max(document.body.scrollHeight, document.documentElement.scrollHeight);
    var marginright = Math.max(document.body.scrollWidth, document.documentElement.scrollWidth);

    var snowsizerange = snowmaxsize - snowminsize;
    for (var i = 0; i <= snowmax; i++) {
        crds[i] = 0;
        lftrght[i] = Math.random() * 15;
        x_mv[i] = 0.03 + Math.random() / 10;
        snow[i] = document.getElementById("s" + i);
        snow[i].style.fontFamily = snowtype[randommaker(snowtype.length)];
        snow[i].size = randommaker(snowsizerange) + snowminsize;
        snow[i].style.fontSize = snow[i].size + "px";
        snow[i].style.color = snowcolor[randommaker(snowcolor.length)];
        snow[i].sink = sinkspeed * snow[i].size / 5;

        // задаём позицию в зависимости от зоны
        if (snowingzone == 1) { snow[i].posx = randommaker(marginright - snow[i].size); }
        if (snowingzone == 2) { snow[i].posx = randommaker(marginright / 2 - snow[i].size); }
        if (snowingzone == 3) { snow[i].posx = randommaker(marginright / 2 - snow[i].size) + marginright / 4; }
        if (snowingzone == 4) { snow[i].posx = randommaker(marginright / 2 - snow[i].size) + marginright / 2; }

        snow[i].posy = randommaker(marginbottom) - snow[i].size;
        snow[i].style.left = snow[i].posx + "px";
        snow[i].style.top = snow[i].posy + "px";
    }
    movesnow();
}

function movesnow() {
    var marginbottom = Math.max(document.body.scrollHeight, document.documentElement.scrollHeight);
    var marginright = Math.max(document.body.scrollWidth, document.documentElement.scrollWidth);

    for (var i = 0; i <= snowmax; i++) {
        crds[i] += x_mv[i];
        snow[i].posy += snow[i].sink;
        snow[i].style.left = snow[i].posx + lftrght[i] * Math.sin(crds[i]) + "px";
        snow[i].style.top = snow[i].posy + "px";

        if (snow[i].posy >= marginbottom - 2 * snow[i].size || parseInt(snow[i].style.left) > (marginright - 3 * lftrght[i])) {
            if (snowingzone == 1) { snow[i].posx = randommaker(marginright - snow[i].size); }
            if (snowingzone == 2) { snow[i].posx = randommaker(marginright / 2 - snow[i].size); }
            if (snowingzone == 3) { snow[i].posx = randommaker(marginright / 2 - snow[i].size) + marginright / 4; }
            if (snowingzone == 4) { snow[i].posx = randommaker(marginright / 2 - snow[i].size) + marginright / 2; }
            snow[i].posy = 0;
        }
    }
    timer = setTimeout(movesnow, 25);
}

// создаём элементы снега
for (var i = 0; i <= snowmax; i++) {
    document.write("<span id='s" + i + "' style='position:absolute;top:-" + snowmaxsize + "px;z-index:99999999;'>" + snowletter + "</span>");
}

if (browserok) {
    window.onload = initsnow;
}