Snow Effect for Winter~ (aka White Album Season)

snow.css

body {
  margin: 0;
  background: #202020;
}

body > .snow {
  display: block;
  position: fixed;
  z-index: 1000;
  top: 0;
  left: 0;
  pointer-events: none;
}

snow.min.js

! function() {
    function n() {
        e.width = window.innerWidth;
        e.height = window.innerHeight;
        r = Math.round(window.innerWidth * window.innerHeight / 1e4)
    }

    function i() {
        var n = window.innerWidth,
            d = window.innerHeight,
            h = e.getContext("2d");
        h.clearRect(0, 0, n, d);
        h.fillStyle = "rgba(255, 255, 255, 0.7)";
        h.beginPath();
        a += .01;
        for (var s = 0; r > s; s++) {
            var m = o[s];
            h.moveTo(m.x, m.y);
            h.arc(m.x, m.y, m.radius, 0, 2 * Math.PI, !0);
            m.y += Math.cos(a) + m.radius / 2;
            m.x += Math.sin(a * m.direction);
            if (m.x > n + 5 || -5 > m.x || m.y > d)
                if (s % 3 > 0) {
                    o[s].x = Math.random() * n;
                    o[s].y = -10
                } else if (Math.sin(a * m.direction) > 0) {
                o[s].x = -5;
                o[s].y = Math.random() * d
            } else {
                o[s].x = n + 5;
                o[s].y = Math.random() * d
            }
        }
        h.fill();
        t(i)
    }
    var e = document.createElement("canvas"),
        t = requestAnimationFrame || msRequestAnimationFrame || function(n) {
            setTimeout(n, 16)
        },
        a = 0,
        r = 0,
        o = [];
    n();
    e.className = "snow";
    document.body.appendChild(e);
    for (var d = 0; r > d; d++) o.push({
        x: Math.random() * window.innerWidth,
        y: Math.random() * window.innerHeight,
        radius: 4 * Math.random() + 1,
        direction: 2 * Math.random() - .5
    });
    addEventListener("resize", n);
    t(i)
}();