var w=window.innerWidth,
    h=window.innerHeight;
c.width=w; c.height=h;
var ctx=c.getContext('2d');
var points=[];
var vels=[];
for(var i=0; i<30; ++i){
  points.push({x:(Math.random()*w)|0, y:(Math.random()*h)|0});
  vels.push({x:(Math.random()-0.5)*4, y:(Math.random()-0.5)*4})
}
function draw(x, y){
  for(var i=0; i<points.length; ++i){
    var endX=points[i].x+vels[i].x;
    var endY=points[i].y+vels[i].y
    
    if(endX<0||endX>w) vels[i].x*=-1;
    if(endY<0||endY>h) vels[i].y*=-1;
    
    points[i].x+=vels[i].x;
    points[i].y+=vels[i].y;
    
    vels[i].x+=(mX-points[i].x)/1000;
    vels[i].y+=(mY-points[i].y)/1000;
    
    ctx.beginPath();
    ctx.moveTo(x, y);
    ctx.lineTo(points[i].x, points[i].y);
    ctx.stroke();
    ctx.closePath();
    
    ctx.beginPath();
    ctx.arc(points[i].x, points[i].y, 2, 0, Math.PI*2);
    ctx.fill();
    ctx.closePath();
  }
}

ctx.strokeStyle='rgba(100, 100, 100, 0.05)';
var mX=w/2,
    mY=h/2;
function anim(){
  window.requestAnimationFrame(anim);
  
  ctx.fillStyle='rgba(0, 0, 0, 0.1)';
  
  ctx.fillRect(0, 0, w, h);
  
  ctx.fillStyle='rgb(100, 100, 10)';
  draw(mX, mY);
}
anim();
document.addEventListener('mousemove', function(e){
  mX=e.clientX;
  mY=e.clientY;
})