Sass mixin that will will allow you to define breakpoints in your Sass code on the fly.when you need to set breakpoints for something, just use them like this:

.my-awesome-element {
    color: red;
}

@include respond-to(648) {
    .my-awesome-element {
        color: green;
    }
}
Or you can do the following:

.my-awesome-element {
    color: red;

    @include respond-to(800) {
        color: blue;
    }

    @include respond-to(520) {
        color: gray;
    }
}