var canvas = document.querySelector('.snow'),
    ctx = canvas.getContext('2d'),
    windowW = window.innerWidth,
    windowH = window.innerHeight,
    numFlakes = 125,
    flakes = [];

if (screen.width < 768) {
    numFlakes = 50;
} // If Mobile

function Flake(x, y) {
    var maxWeight = 5,
        maxSpeed = 1.2;

    if (screen.width < 768) {
        maxSpeed = 1;
    } // If Mobile

    this.x = x;
    this.y = y;
    this.r = randomBetween(0, 1);
    this.a = randomBetween(0, Math.PI);
    this.aStep = 0.01;

    this.weight = randomBetween(2, maxWeight);
    this.alpha = (this.weight / maxWeight);
    this.speed = (this.weight / maxWeight) * maxSpeed;

    this.update = function () {
        this.x += Math.cos(this.a) * this.r;
        this.a += this.aStep;

        this.y += this.speed;
    }
}

function init() {
    var i = numFlakes,
        flake,
        x,
        y;

    while (i--) {
        x = randomBetween(0, windowW, true);
        y = randomBetween(0, windowH, true);

        flake = new Flake(x, y);
        flakes.push(flake);
    }

    scaleCanvas();
    loop();
}

function scaleCanvas() {
    canvas.width = windowW;
    canvas.height = windowH;
}

function loop() {
    var i = flakes.length,
        z,
        dist,
        flakeA,
        flakeB;

    // clear canvas
    ctx.save();
    ctx.setTransform(1, 0, 0, 1, 0, 0);
    ctx.clearRect(0, 0, windowW, windowH);
    ctx.restore();

    // loop of hell
    while (i--) {

        flakeA = flakes[i];
        flakeA.update();


        /*for (z = 0; z < flakes.length; z++) { flakeB=flakes[z]; if (flakeA !==flakeB && distanceBetween(flakeA,
          flakeB) < 150) { ctx.beginPath(); ctx.moveTo(flakeA.x, flakeA.y); ctx.lineTo(flakeB.x, flakeB.y);
          ctx.strokeStyle='#444444' ; ctx.stroke(); ctx.closePath(); } }*/

        ctx.beginPath();
        ctx.arc(flakeA.x, flakeA.y, flakeA.weight, 0, 2 * Math.PI, false);
        ctx.fillStyle = 'rgba(255, 255, 255, ' + flakeA.alpha + ')';
        ctx.fill();

        if (flakeA.y >= windowH) {
            flakeA.y = -flakeA.weight;
        }
    }

    requestAnimationFrame(loop);
}

function randomBetween(min, max, round) {
    var num = Math.random() * (max - min + 1) + min;

    if (round) {
        return Math.floor(num);
    } else {
        return num;
    }
}

function distanceBetween(vector1, vector2) {
    var dx = vector2.x - vector1.x,
        dy = vector2.y - vector1.y;

    return Math.sqrt(dx * dx + dy * dy);
}

init();