#functions {
  @var: 10;
  @colors: #000, #fff;
  color: _color("evil red"); // #660000
  width: increment(15);
  height: undefined("self");
  border-width: add(2, 3);
  variable: increment(@var);
  background: linear-gradient(@colors);
}

#built-in {
  @r: 32;
  escaped: e("-Some::weird(#thing, y)");
  lighten: lighten(#ff0000, 40%);
  darken: darken(#ff0000, 40%);
  saturate: saturate(#29332f, 20%);
  desaturate: desaturate(#203c31, 20%);
  greyscale: greyscale(#203c31);
  spin-p: spin(hsl(340, 50%, 50%), 40);
  spin-n: spin(hsl(30, 50%, 50%), -40);
  luma-white: luma(#fff);
  luma-black: luma(#000);
  luma-black-alpha: luma(rgba(0,0,0,0.5));
  luma-red: luma(#ff0000);
  luma-green: luma(#00ff00);
  luma-blue: luma(#0000ff);
  luma-yellow: luma(#ffff00);
  luma-cyan: luma(#00ffff);
  luma-white-alpha: luma(rgba(255,255,255,0.5));
  contrast-filter: contrast(30%);
  contrast-white: contrast(#fff);
  contrast-black: contrast(#000);
  contrast-red: contrast(#ff0000);
  contrast-green: contrast(#00ff00);
  contrast-blue: contrast(#0000ff);
  contrast-yellow: contrast(#ffff00);
  contrast-cyan: contrast(#00ffff);
  contrast-light: contrast(#fff, #111111, #eeeeee);
  contrast-dark: contrast(#000, #111111, #eeeeee);
  contrast-light-thresh: contrast(#fff, #111111, #eeeeee, 0.5);
  contrast-dark-thresh: contrast(#000, #111111, #eeeeee, 0.5);
  contrast-high-thresh: contrast(#555, #111111, #eeeeee, 0.6);
  contrast-low-thresh: contrast(#555, #111111, #eeeeee, 0.1);
  format: %("rgb(%d, %d, %d)", @r, 128, 64);
  format-string: %("hello %s", "world");
  format-multiple: %("hello %s %d", "earth", 2);
  format-url-encode: %('red is %A', #ff0000);
  eformat: e(%("rgb(%d, %d, %d)", @r, 128, 64));
  
  unitless: unit(12px);
  unit: unit(13px + 1px, em);

  hue: hue(hsl(98, 12%, 95%));
  saturation: saturation(hsl(98, 12%, 95%));
  lightness: lightness(hsl(98, 12%, 95%));
  red: red(#f00);
  green: green(#0f0);
  blue: blue(#00f);
  rounded: round(@r/3);
  rounded-two: round(@r/3, 2);
  roundedpx: round(10px / 3);
  roundedpx-three: round(10px / 3, 3);
  rounded-percentage: round(10.2%);
  ceil: ceil(10.1px);
  floor: floor(12.9px);
  percentage: percentage(10px / 50);
  color: color("#ff0011");
  tint: tint(#777777, 13);
  tint-full: tint(#777777, 100);
  tint-percent: tint(#777777, 13%);
  shade: shade(#777777, 13);
  shade-full: shade(#777777, 100);
  shade-percent: shade(#777777, 13%);
  
  hsv: hsv(5, 50%, 30%);
  hsva: hsva(3, 50%, 30%, 0.2);

  mix: mix(#ff0000, #ffff00, 80);
  mix-0: mix(#ff0000, #ffff00, 0);
  mix-100: mix(#ff0000, #ffff00, 100);
  mix-weightless: mix(#ff0000, #ffff00);

  .is-a {
    color: iscolor(#ddd);
    color1: iscolor(red);
    color2: iscolor(rgb(0, 0, 0));
    keyword: iskeyword(hello);
    number: isnumber(32);
    string: isstring("hello");
    pixel: ispixel(32px);
    percent: ispercentage(32%);
    em: isem(32em);
  }
}

#alpha {
  alpha: darken(hsla(25, 50%, 50%, 0.6), 10%);
}

#blendmodes {
  multiply: multiply(#f60000, #f60000);
  screen: screen(#f60000, #0000f6);
  overlay: overlay(#f60000, #0000f6);
  softlight: softlight(#f60000, #ffffff);
  hardlight: hardlight(#f60000, #0000f6);
  difference: difference(#f60000, #0000f6);
  exclusion: exclusion(#f60000, #0000f6);
  average: average(#f60000, #0000f6);
  negation: negation(#f60000, #313131);
}