@function min($value1, $value2: 0) {
    @if type-of($value1) == list {
        $min: nth($value1, 1);

        @if is-null($min) {
            $min: 0;
        }

        @each $item in $value1 {
            @if is-null($item) {
                $item: 0;
            }
            @if ($item < $min) {
                $min: $item;
            }
        }

        @return $min;
    } @else {
        @if is-null($value1) {
            $value1: 0;
        }
        @if is-null($value2) {
            $value2: 0;
        }
        @if $value1 > $value2 {
            @return $value2;
        }
        @else if $value2 > $value1 {
            @return $value1;
        }
    }

    @return $value1;
}

@function max($value1, $value2: 0) {
    @if type-of($value1) == list {
        $max: nth($value1, 1);

        @if is-null($max) {
            $max: 0;
        }

        @each $item in $value1 {
            @if is-null($item) {
                $item: 0;
            }
            @if ($item > $max) {
                $max: $item;
            }
        }

        @return $max;
    } @else {
        @if is-null($value1) {
            $value1: 0;
        }
        @if is-null($value2) {
            $value2: 0;
        }
        @if $value1 > $value2 {
            @return $value1;
        }
        @else if $value2 > $value1 {
            @return $value2;
        }
    }

    @return $value1;
}

@function x($position) {
    @return parsebox($position, 1);
}
@function y($position) {
    @return parsebox($position, 2);
}

@function before($position) {
    @return parsebox($position, 1);
}
@function after($position) {
    @return parsebox($position, 2);
}

@function top($box, $fallbackBox) {
    @if $box == null {
        $box: $fallbackBox;
    }
    @return parsebox($box, 1);
}
@function right($box, $fallbackBox) {
    @if $box == null {
        $box: $fallbackBox;
    }
    @return parsebox($box, 2);
}
@function bottom($box, $fallbackBox) {
    @if $box == null {
        $box: $fallbackBox;
    }
    @return parsebox($box, 3);
}
@function left($box, $fallbackBox) {
    @if $box == null {
        $box: $fallbackBox;
    }
    @return parsebox($box, 4);
}
@function vertical($box, $fallbackBox) {
    @if $box == null {
        $box: $fallbackBox;
    }
    @return top($box) + bottom($box);
}
@function horizontal($box, $fallbackBox) {
    @if $box == null {
        $box: $fallbackBox;
    }
    @return left($box) + right($box);
}
@function boxmax($box, $fallbackBox) {
    @if $box == null {
        $box: $fallbackBox;
    }
    @return max(max(top($box), right($box)), max(bottom($box), left($box)));
}
@function boxmin($box, $fallbackBox) {
    @if $box == null {
        $box: $fallbackBox;
    }
    @return min(min(top($box), right($box)), min(bottom($box), left($box)));
}
@function rotate90($box) {
    @return left($box) top($box) right($box) bottom($box);
}
@function rotate180($box) {
    @return bottom($box) left($box) top($box) right($box);
}

@function rotate270($box) {
    @return right($box) bottom($box) left($box) top($box);
}
@function flip-vertical($box) {
    @return bottom($box) right($box) top($box) left($box);
}
@function flip-horizontal($box) {
    @return top($box) left($box) bottom($box) right($box);
}
@function rtl($box) {
    @return top($box) left($box) bottom($box) right($box);
}

@function rtl-background-position($pos) {
    $x: parsebox($pos, 1);
    $new-x: null;
    @if $x == right or $x == 100% {
        $new-x: 0;
    } @else if $x == 0 or $x == left {
        $new-x: right;
    } @else {
        $new-x: $x;
    }
    @return $new-x parsebox($pos, 2);
}

@function nopx ($value) {
    @if $value == 0 {
        @return 0;
    }
    @return $value / 1px;
}