$breakpoints: (
    xs: 599px,
    sm: 959px,
    md: 1199px,
    lg: 1599px
);

@mixin set-breakpoint-lower($breakpoint) {
    @if map-has-key($map: $breakpoints, $key: $breakpoint) {

        // Get the value from breakpoint
        $breakpoint-value: map-get($breakpoints, $breakpoint);

        @media screen and (max-width: $breakpoint-value) {
            @content;
        }
    } @else {
        @warn 'Invalid breakpoint: #{$breakpoint}'
    }
};

@mixin set-breakpoint-between($lower, $upper) {
    @if map-has-key($breakpoints, $lower) and map-has-key($breakpoints, $upper) {

        $lower-point: map-get($breakpoints, $lower);
        $upper-point: map-get($breakpoints, $upper);

        @media (min-width: $lower-point + 1) and (max-width: $upper-point) {
            @content;
        }

    } @else {
        @if (map-has-key($breakpoints, $lower) == false) {
            @warn 'Invalid lower breakpoint: #{$lower}'
        };

        @if (map-has-key($breakpoints, $upper) == false) {
            @warn 'Invalid upper breakpoint: #{$upper}'
        };
    }
};

@mixin set-breakpoint-upper($breakpoint) {
    @if map-has-key($breakpoints, $breakpoint) {
        $breakpoint-value: map-get($breakpoints, $breakpoint);

        @media screen and (min-width: $breakpoint-value + 1) {
            @content;
        }
    }
}