var
snow_flake_image = 'js/schneeflocke.png';
snow_size_min = 10,
snow_size_max = 15,
snow_num_flakes = 100,
snow_horiz_start = 0,
snow_horiz_end = document.getElementById('bg').offsetWidth-10,
snow_vert_start = 0,
snow_vert_end = document.getElementById('page').offsetHeight,
snow_flake_color = '#808080',
snow_fall_speed = 30;

(function () {
        var _int_snow = function () {
                debugger;
                var
                        size_min = (typeof (snow_size_min) != 'undefined') ? snow_size_min : 8,
                        size_max = (typeof (snow_size_max) != 'undefined') ? snow_size_max : 20,
                        num_flakes = (typeof (snow_num_flakes) != 'undefined') ? snow_num_flakes : 20,
                        horiz_start = (typeof (snow_horiz_start) != 'undefined') ? snow_horiz_start : 0,
                        horiz_end =
                                (typeof (snow_horiz_end) != 'undefined') ?
                                snow_horiz_end :
                                (document.body.clientWidth || document.body.innerWidth || document.body.offsetWidth),
                        vert_start = (typeof (snow_vert_start) != 'undefined') ? snow_vert_start : 0,
                        vert_end =
                                (typeof (snow_vert_end) != 'undefined') ?
                                snow_vert_end :
                                (document.body.clientHeight || document.body.innerHeight || document.body.offsetHeight),
                        flake_image = (typeof (snow_flake_image) != 'undefined') ? snow_flake_image : null,
                        flake_color = (typeof (snow_flake_color) != 'undefined') ? snow_flake_color : '#A0A0A0',
                        fall_speed = (typeof (snow_fall_speed) != 'undefined') ? snow_fall_speed : 20,
                        flake_objects = [],
                        flakes_per_ms = num_flakes * fall_speed / (vert_end - vert_start) / 1000,
                        flakes_limit = 0,
                        time_start = new Date ().getTime ();

                setInterval (
                        function () {
                                var _int_flake_move = function (time_current) {
                                        var i, one_flake, time_diff;

                                        for (i = 0; i < flake_objects.length; ++i) {
                                                one_flake = flake_objects [i];
                                                time_diff = time_current - one_flake.time_start;
                                                one_flake.pos_vert_current = one_flake.pos_vert_start + time_diff * fall_speed / 1000;
                                                one_flake.dom.style.top = one_flake.pos_vert_current + 'px';
                                                one_flake.pos_horiz_current += Math.floor (Math.random () * 3 - 1);
                                                if (one_flake.pos_horiz_current < horiz_start) {
                                                        one_flake.pos_horiz_current = horiz_start;
                                                } else if (one_flake.pos_horiz_current + one_flake.size > horiz_end) {
                                                        one_flake.pos_horiz_current = horiz_end - one_flake.size;
                                                }
                                                one_flake.dom.style.left = one_flake.pos_horiz_current + 'px';
                                        }
                                };

                                var _int_flake_cleanup = function () {
                                        var limit;

                                        limit = vert_end - size_max;
                                        while (flake_objects.length && (flake_objects [0].pos_vert_current >= limit)) {
                                                document.body.removeChild (flake_objects [0].dom);
                                                flake_objects.shift ();
                                        }
                                };

                                var _int_flake_add = function (time_current) {
                                        var current_size, current_flake, px_size, pos_horiz, pos_vert;

                                        current_size = Math.floor (Math.random () * (size_max - size_min + 1)) + size_min;
                                        px_size = current_size + 'px';
                                        pos_horiz = Math.random () * (horiz_end - horiz_start - current_size + 1) + horiz_start;
                                        pos_vert = vert_start || -current_size;
                                        if (flake_image !== null) {
                                                one_flake = document.createElement ('img');
                                                one_flake.src = flake_image;
                                                one_flake.style.display = 'block';
                                        } else {
                                                one_flake = document.createElement ('div');
                                                one_flake.appendChild (document.createTextNode ('*'));
                                                one_flake.style.color = flake_color;
                                                one_flake.style.fontSize = px_size;
                                        }
                                        one_flake.style.position = 'absolute';
                                        one_flake.style.zIndex = '1000000';
                                        one_flake.style.width = px_size;
                                        one_flake.style.height = px_size;
                                        one_flake.style.top = pos_vert + 'px';
                                        one_flake.style.left = pos_horiz + 'px';
                                        flake_objects.push ({
                                                dom: one_flake,
                                                size: current_size,
                                                time_start: time_current,
                                                pos_horiz_current: pos_horiz,
                                                pos_vert_start: pos_vert,
                                                pos_vert_current: pos_vert
                                        });
                                        document.body.appendChild (one_flake);
                                };

                                var time_current, flakes_limit, flakes_active;

                                time_current = new Date ().getTime ();
                                _int_flake_move (time_current);
                                _int_flake_cleanup ();
                                flakes_limit = Math.floor ((time_current - time_start) * flakes_per_ms) + 1;
                                for (;;) {
                                        flakes_active = flake_objects.length;
                                        if ((flakes_active >= flakes_limit) || (flakes_active >= num_flakes)) {
                                                break;
                                        }
                                        _int_flake_add (time_current);
                                }
                        },
                        100
                );
        };

        if ('addEventListener' in window) {
                window.addEventListener ('load', _int_snow, false);
        } else if ('attachEvent' in document) {
                window.attachEvent ('onload', _int_snow);
        } else {
                window.onload = _int_snow;
        }
}) ();