CSS random div placement & responsiveness

I created a starry night animation but was wondering if anyone had a better way to place divs "randomly" with only CSS ??? Also, I'm having difficulty with responsiveness as well. Thank you for your time! just trying to learn.

check the complete code at http://codepen.io/anon/pen/MeeYWO?editors=1100

#star-bl:nth-of-type(5) {
    left: -350px;
    top: 225px;
}

#star-bl:nth-of-type(6) {
    left: 750px;
    top: 250px;
}

#star-bl:nth-of-type(7) {
    left: -450px;
}

#star-sm:nth-of-type(8) {
    left: -225px;
}

#star-sm:nth-of-type(9) {
    left: 500px;
}

#star-sm:nth-of-type(10) {
    left: -100px;
}