[CSS3] Responsive Navigation Menu

This code will display depending on the screen resolution. For larger screens, 678px or greater, it will display a title along with the menu items. For anything smaller, it will display a site title along with a hamburger menu icon, and a full-screen navigation is displayed when the hamburger menu icon is clicked.

This does not require any JavaScript, but does require the :has pseudo-class (caniuse).

HTML:

HTML Code:

---

<header class="global-navigation">
  <nav>
    <h1>Site Title</h1>
    <ul>
      <li><a href="#" class="active">Home</a></li>
      <li><a href="#">About</a></li>
      <li><a href="#">Contact</a></li>
    </ul>
    <input id="global-navigation-toggle" type="checkbox" class="toggle-mobile-menu" hidden>
    <label for="global-navigation-toggle" class="icon-hamburger" aria-label="Open menu"></label>
  </nav>
  <aside>
    <section>
      <h2>Navigation</h2>
      <label for="global-navigation-toggle" aria-label="Close menu">&times;</label>
    </section>
    <ul>
      <li><a href="#" class="active">Home</a></li>
      <li><a href="#">About</a></li>
      <li><a href="#">Contact</a></li>
      <li>
          <label for="global-navigation-toggle" aria-label="Close menu">Close</label>
      </li>
    </ul>
  </aside>
</header>

---

CSS:

Code:

---

/* theme colors, change once here */
:root {
  --nav-background-color: #555555;
  --nav-color: #fefefa;
  --nav-link-active: #ffdc31;
  --aside-background-color: #fefefa;
  --aside-color: #555555;
  --aside-active-background-color: rgba(85, 85, 85, 0.94);
  --site-title-size: 2rem;
}

/* normalization */
body, html {
  font-family: Arial, sans-serif;
  font-size: 16px;
  margin: 0;
  padding: 0;
}

/* icon */
.icon-hamburger {
  width: 28px; height: 20px; border: 0; background: none; cursor: pointer;
  background-image:
    linear-gradient(currentColor, currentColor),
    linear-gradient(currentColor, currentColor),
    linear-gradient(currentColor, currentColor);
  background-repeat: no-repeat;
  background-size: 100% 2px, 100% 2px, 100% 2px;
  background-position: 0 0, 0 9px, 0 18px;
}

/* desktop view */
.global-navigation {
  background-color: var(--nav-background-color);
  color: var(--nav-color);
}

.global-navigation > nav {
  align-items: center;
  display: flex;
  margin: 0 auto;
  max-width: clamp(768px, 80vw, 1400px);
  padding: 1rem clamp(1.25rem, 2vw, 10rem);
}

.global-navigation > nav > h1 {
  font-size: var(--site-title-size);
}

.global-navigation > nav > label {
  display: none;
  color: var(--nav-color);
}

.global-navigation > nav > ul {
  align-items: center;
  display: flex;
  flex-grow: 1;
  justify-content: flex-end;
  list-style-type: none;
}

.global-navigation > nav > ul > li:not(:last-of-type) {
  margin-right: 1.5rem;
}

.global-navigation > nav > ul > li > a {
  border-bottom: none;
  color: var(--nav-color);
  opacity: 1;
  text-decoration: none;
  transition: opacity 0.3s ease;
}

.global-navigation > nav > ul > li > a.active {
  color: var(--nav-link-active);
}

.global-navigation > nav > ul:hover > li > a {
  border-bottom: none;
  opacity: 0.5;
}

.global-navigation > nav > ul > li:hover > a {
  border-bottom: 1px solid;
  opacity: 1;
}

.global-navigation > aside {
  display: none;
}

/* mobile view */
@media (max-width: 767.98px)
{
  .global-navigation > nav {
    justify-content: space-between;
  }
 
  .global-navigation > nav > ul {
    display: none;
  }

  .global-navigation > nav > label {
    display: initial;
  }

  .global-navigation > aside {
    background-color: var(--aside-background-color);
    color: var(--aside-color);
    display: flex;
    flex-direction: column;
    height: 100vh;
    inset: 0;
    opacity: 0;
    pointer-events: none;
    position: fixed;
    transform: translateX(100%);
    transition: transform .25s ease, opacity .2s ease, visibility 0s linear .25s;
    visibility: hidden;
    width: 100vw;
    z-index: 999;
  }

  .global-navigation:has(.toggle-mobile-menu:checked) > aside {
    transform: translateX(0);
    transition: transform .25s ease, opacity .2s ease;
    opacity: 1;
    pointer-events: auto;
    visibility: visible;
  }

  .global-navigation > aside > section {
    align-items: center;
    background-color: var(--nav-background-color);
    color: var(--nav-color);
    display: flex;
    justify-content: space-between;
    padding: 1rem clamp(1.25rem, 2vw, 10rem);
  }

  .global-navigation > aside > section > h2 {
    flex-grow: 1;
    font-size: var(--site-title-size);
    text-align: center;
  }

  .global-navigation > aside > section > label {
    cursor: pointer;
    font-size: var(--site-title-size);
  }

  .global-navigation > aside > ul {
    flex-grow: 1;
    list-style: none;
    margin: 0;
    padding: 0;
    display: flex;
    flex-direction: column;
    overflow-y: auto;
  }

  .global-navigation > aside > ul > li > a,
  .global-navigation > aside > ul > li:last-child > label {
    display: block;
    padding: 0.875rem clamp(1.25rem, 2vw, 10rem);
    text-decoration: none;
    color: var(--aside-color);
    line-height: 44px;
    min-height: 44px;
    transition: background-color .2s ease, color .2s ease, opacity .2s ease;
    border-bottom: 1px solid rgba(0,0,0,.06);
    position: relative;
  }

  .global-navigation > aside > ul > li > a.active {
    background: linear-gradient(0deg, var(--aside-active-background-color), var(--aside-active-background-color));
    color: var(--nav-link-active);
    font-weight: bold;
  }
  .global-navigation > aside > ul > li > a.active::before {
    content: "";
    position: absolute;
    left: 0;
    top: 0;
    bottom: 0;
    width: 0.25rem;
    background: var(--nav-link-active);
  }

  .global-navigation > aside > ul > li > a:hover,
  .global-navigation > aside > ul > li:last-child > label:hover {
    background: linear-gradient(0deg, var(--aside-active-background-color), var(--aside-active-background-color));
    color: var(--nav-link-active);
  }

  .global-navigation > aside > ul > li:last-child {
    margin-top: auto;
  }

  .global-navigation > aside > ul > li:last-child > label {
    cursor: pointer;
  }
}

---

Demo: https://jsfiddle.net/9odm4q27/