snowfall.dart

void snowFall(){
  // draw background on canvas
  ctx.fillStyle="#000";
  ctx.fillRect(0,0,W,H);
  
  //drawing intitial snowflakes on canvas
  ctx.fillStyle = "#fff";
  // rain 
  ctx.beginPath();
  
  for(var i = 0; i < maxFlakes; i++){
    var f = flakes[i];
    ctx.moveTo(f._x, f._y);
    ctx.arc(f._x, f._y, f._r, 0, math.PI*2, true);
  }
  ctx.fill();
  
  //moving snow flakes
  var angl=0;
  for(var i=0; i < maxFlakes; i++){
    angl+=0.1;
    var f=flakes[i];
    f._x +=math.sin(angl).abs() + 0.1 ;
    f._y += math.cos(angl).abs() * speed;
    //resetting snowflakes when they are out of frame
    if(f._x > W || f._x < 0 || f._y > H){
      f._x = rng.nextDouble() * W;
      f._y=-10.0;
    }
  }
  
}