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CSS

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CSS Base

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JavaScript

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HTML 

              
                <section class="no-js">
  <button id="dark-mode-toggle">Toggle Dark Mode</button>
  <button id="light-mode-toggle">Toggle Light Mode</button>

  <h3>Primary</h3>
  <ul class="sg-colors">
    <li><span class="sg-swatch sg-swatch-primary-dark"></span></li>
    <li><span class="sg-swatch sg-swatch-primary"></span></li>
    <li><span class="sg-swatch sg-swatch-primary-light"></span></li>
  </ul>
  <h3>Secondary</h3>
  <ul class="sg-colors">
    <li><span class="sg-swatch sg-swatch-secondary-dark"></span></li>
    <li><span class="sg-swatch sg-swatch-secondary"></span></li>
    <li><span class="sg-swatch sg-swatch-secondary-light"></span></li>
  </ul>
  <h3>Grey</h3>
  <ul class="sg-colors">
    <li><span class="sg-swatch sg-swatch-grey-dark"></span></li>
    <li><span class="sg-swatch sg-swatch-grey"></span></li>
    <li><span class="sg-swatch sg-swatch-grey-light"></span></li>
  </ul>
  <h3>Alerts</h3>
  <ul class="sg-colors">
    <li><span class="sg-swatch sg-swatch-alert"></span></li>
    <li><span class="sg-swatch sg-swatch-info"></span></li>
    <li><span class="sg-swatch sg-swatch-success"></span></li>
    <li><span class="sg-swatch sg-swatch-warning"></span></li>
  </ul>
  <h3>Util</h3>
  <ul class="sg-colors">
    <li><span class="sg-swatch sg-swatch-bg"></span></li>
    <li><span class="sg-swatch sg-swatch-text"></span></li>
  </ul>
  <div class="text">
    <h1>Heading Level 1</h1>
    <p>Lorem ipsum dolor sit amet consectetur adipisicing elit. Laboriosam accusamus, fuga illum ut aut voluptas maxime, eaque in dolore temporibus sequi totam earum veritatis odit. Ex nemo suscipit aliquid doloribus! <a href="#">This is a text link</a>.</p>    
    <h2>Heading Level 2</h2>
    <p>Lorem ipsum dolor sit amet consectetur adipisicing elit. Vel similique perferendis molestias quos sint cupiditate dolor, ducimus, odio debitis enim aspernatur, possimus voluptate deserunt harum adipisci nihil nesciunt minus. Pariatur.</p>
    <p>Lorem ipsum dolor sit amet consectetur adipisicing elit. Vel similique perferendis molestias quos sint cupiditate dolor, ducimus, odio debitis enim aspernatur, possimus voluptate deserunt harum adipisci nihil nesciunt minus. Pariatur.</p>
    <h3>Heading Level 3</h3>
    <p>Lorem ipsum dolor sit amet consectetur adipisicing elit. Vel similique perferendis molestias quos sint cupiditate dolor, ducimus, odio debitis enim aspernatur, possimus voluptate deserunt harum adipisci nihil nesciunt minus. Pariatur.</p>
  </div>
</section>
!

CSS 

              
                /* ==========================================================================
   Color Variables
   ========================================================================== */
/* LIGHT */
$c-primary: #380021;
$c-primary-dark: darken($c-primary, 5%);
$c-primary-light: lighten($c-primary, 15%);
$c-secondary: #cc284e;
$c-secondary-dark: darken($c-secondary, 15%);
$c-secondary-light: lighten($c-secondary, 15%);
$c-grey: #7b7274;
$c-grey-dark: darken($c-grey, 20%);
$c-grey-light: lighten($c-grey, 20%);
$c-alert: #ab0000;
$c-info: #000459;
$c-success: #115832;
$c-warning: #6b5f13;
$c-bg: #fff7f9;
$c-text: #1e1719;

/* DARK */
$c-dark-primary: #ff70c3; // ff0095
$c-dark-primary-dark: desaturate(darken($c-dark-primary, 35%), 15%);
$c-dark-primary-light: lighten($c-dark-primary, 10%);
$c-dark-secondary: #fa6285; // dd5474;
$c-dark-secondary-dark: desaturate(darken($c-dark-secondary, 25%), 15%);
$c-dark-secondary-light: lighten($c-dark-secondary, 12%);
$c-dark-grey: #2b2328;
$c-dark-grey-dark: darken($c-dark-grey, 5%);
$c-dark-grey-light: lighten($c-dark-grey, 26%);
$c-dark-alert: #ec768c;
$c-dark-info: #b8baeb;
$c-dark-success: #5be69b;
$c-dark-warning: #d6d332;
$c-dark-bg: #1f0012;
$c-dark-text: #ffd6ee;

:root {
  --c-primary: #{$c-primary};
  --c-primary-dark: #{$c-primary-dark};
  --c-primary-light: #{$c-primary-light};
  --c-secondary: #{$c-secondary};
  --c-secondary-dark: #{$c-secondary-dark};
  --c-secondary-light: #{$c-secondary-light};
  --c-grey: #{$c-grey};
  --c-grey-dark: #{$c-grey-dark};
  --c-grey-light: #{$c-grey-light};
  --c-alert: #{$c-alert};
  --c-info: #{$c-info};
  --c-success: #{$c-success};
  --c-warning: #{$c-warning};
  --c-bg: #{$c-bg};
  --c-text: #{$c-text};
}

/* ==========================================================================
   Demo styling
   ========================================================================== */
.sg-colors {
  margin: 0;
  padding: 0;

  li {
    display: inline-block;
    text-align: center;
  }
}

.sg-swatch {
  box-shadow: 0 2px 5px 2px hsla(0, 0%, 50%, 0.4);
  display: block;
  height: 130px;
  margin: 30px 5px;
  position: relative;
  width: 130px;

  &:after {
    left: 0;
    padding-top: 0.5em;
    position: absolute;
    text-align: center;
    top: 100%;
    width: 100%;
  }

  &:before {
    color: black;
    display: block;
    padding-top: 0.5em;
    position: absolute;
    text-align: center;
    text-shadow: 0 0 4px #fff, 0 0 8px #fff, 0 0 12px #fff, 0 0 12px #fff,
      0 0 12px #fff;
    width: 100%;
  }
}

$sgSwatchList: (
  "primary" $c-primary,
  "primary-dark" $c-primary-dark,
  "primary-light" $c-primary-light,
  "secondary" $c-secondary,
  "secondary-dark" $c-secondary-dark,
  "secondary-light" $c-secondary-light,
  "text" $c-text,
  "grey-dark" $c-grey-dark,
  "grey" $c-grey,
  "grey-light" $c-grey-light,
  "bg" $c-bg,
  "alert" $c-alert,
  "info" $c-info,
  "success" $c-success,
  "warning" $c-warning,
);

@each $s in $sgSwatchList {
  .sg-swatch-#{nth($s, 1)} {
    background-color: nth($s, 2);

    &:after {
      content: ".c-#{nth($s, 1)}";
    }

    &:before {
      content: "#{nth($s, 2)}";
    }
  }
}

html,
body {
  box-sizing: border-box;
}

section {
  background-color: var(--c-bg);
  color: var(--c-text);
  overflow: auto;
  padding: 1rem;
}

a,
a:visited {
  color: var(--c-secondary);

  &:hover,
  &:focus {
    color: var(--c-secondary-dark);
  }
}

button {
  align-items: center;
  background: var(--c-secondary);
  background: linear-gradient(
    to right,
    var(--c-secondary-dark),
    var(--c-secondary-dark) 34%,
    var(--c-secondary) 66%
  );
  background-position: 100%;
  background-size: 300% 100%;
  border: 0;
  border-radius: 4px;
  box-shadow: 0 2px 5px 0 rgba(0, 0, 0, 0.16), 0 2px 10px 0 rgba(0, 0, 0, 0.12);
  color: var(--c-bg);
  display: inline-block;
  height: auto;
  line-height: 1.15;
  overflow: hidden;
  padding: 12px 24px;
  position: relative;
  text-align: center;
  text-decoration: none;
  vertical-align: middle;
}

h1,
h2,
h3 {
  color: var(--c-primary-light);
}

/* ==========================================================================
   Dark Mode Modifications (usually in a separate file, inline because of CodePen)
   ========================================================================== */
@mixin dark-mode {
  --c-primary: #{$c-dark-primary};
  --c-primary-dark: #{$c-dark-primary-dark};
  --c-primary-light: #{$c-dark-primary-light};
  --c-secondary: #{$c-dark-secondary};
  --c-secondary-dark: #{$c-dark-secondary-dark};
  --c-secondary-light: #{$c-dark-secondary-light};
  --c-grey: #{$c-dark-grey};
  --c-grey-dark: #{$c-dark-grey-dark};
  --c-grey-light: #{$c-dark-grey-light};
  --c-alert: #{$c-dark-alert};
  --c-info: #{$c-dark-info};
  --c-success: #{$c-dark-success};
  --c-warning: #{$c-dark-warning};
  --c-bg: #{$c-dark-bg};
  --c-text: #{$c-dark-text};

  $sgSwatchListDark: (
    "primary" $c-dark-primary,
    "primary-dark" $c-dark-primary-dark,
    "primary-light" $c-dark-primary-light,
    "secondary" $c-dark-secondary,
    "secondary-dark" $c-dark-secondary-dark,
    "secondary-light" $c-dark-secondary-light,
    "text" $c-dark-text,
    "grey-dark" $c-dark-grey-dark,
    "grey" $c-dark-grey,
    "grey-light" $c-dark-grey-light,
    "bg" $c-dark-bg,
    "alert" $c-dark-alert,
    "info" $c-dark-info,
    "success" $c-dark-success,
    "warning" $c-dark-warning,
  );

  @each $s in $sgSwatchListDark {
    .sg-swatch-#{nth($s, 1)} {
      background-color: nth($s, 2);

      &:after {
        content: ".c-#{nth($s, 1)}";
      }

      &:before {
        content: "#{nth($s, 2)}";
      }
    }
  }

}

/* ==========================================================================
   Applying colors based on `prefers-color-scheme` first, then user selection in `data-color-scheme`
   ========================================================================== */
@media (prefers-color-scheme: dark) {
  section.no-js {
    @include dark-mode;
  }
}

[data-color-scheme="dark"] {
    @include dark-mode;
}
!

JS 

              
                let BeInclusive = {};

BeInclusive.Utils = {
  /**
   * Set the current color scheme to the provided `currentTheme`, overriding the default
   * 
   * @param {string} currentTheme 
   */
  colorSchemeSet: function(currentTheme) {
    let containerElement = document.getElementsByTagName("section")[0];
    if (currentTheme == "dark") {
      containerElement.dataset.colorScheme = "dark";
    } else {
      containerElement.dataset.colorScheme = "light";
    }

    localStorage.setItem("theme", currentTheme);

    return currentTheme;
  },
  /**
   * Triggers the color scheme setting when the OS `prefers-color-scheme` value changes
   * 
   * @param {Event} e 
   */
  colorSchemeTrigger: function(e) {
    let prefersDarkScheme = e;

    if (prefersDarkScheme.matches) {
      return this.colorSchemeSet("dark");
    } else {
      return this.colorSchemeSet("light");
    }
  },
  /**
   * Initializes the color schene settings based on localStorage, defaults to 
   * `prefers-color-scheme` if no localStorage value is set.
   */
  colorSchemeInit: function() {
    window
      .matchMedia("(prefers-color-scheme: dark)")
      .addEventListener("change", e => this.colorSchemeTrigger(e));

    let currentTheme = localStorage.getItem("theme");

    if (["dark", "light"].indexOf(currentTheme) == -1) {
      return this.colorSchemeTrigger(
        window.matchMedia("(prefers-color-scheme: dark)")
      );
    } else {
      if (currentTheme == "dark") {
        return this.colorSchemeSet("dark");
      } else {
        return this.colorSchemeSet("light");
      }
    }
  },
};

// (This should be <body> or <html>, changed to section here so it can run in CodePen)
let containerElement = document.getElementsByTagName("section")[0];
let toggleDark = document.getElementById('dark-mode-toggle');
let toggleLight = document.getElementById('light-mode-toggle');

containerElement.classList.remove("no-js");
toggleDark.addEventListener("click", e => BeInclusive.Utils.colorSchemeSet('dark'));
toggleLight.addEventListener("click", e => BeInclusive.Utils.colorSchemeSet('light'));
BeInclusive.Utils.colorSchemeInit();
!
999px

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