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About the <head>

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!
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CSS

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HTML 

              
                <header class="header">
  <a class="header__logo" href="#">
    <span class="logo__title">John Doe</span>
    <img class="logo__image" src="https://i.imgur.com/Q4LtrpQ.png" alt="John Doe">
  </a>
  <nav class="header__nav">
    <ul class="header__list">
      <li><a class="header__link" href="#">Home</a></li>
      <li><a class="header__link" href="#">About</a></li>
      <li><a class="header__link" href="#">Contact</a></li>
    </ul>
  </nav>
  <div class="burger">
    <svg width="24px" height="24px" viewBox="0 0 24 24" xmlns="http://www.w3.org/2000/svg">
      <g stroke="none" stroke-width="1" fill="none" fill-rule="evenodd">
        <g id="ic_fluent_navigation_24_regular" fill="#ffffff" fill-rule="nonzero">
          <path d="M2.75254822,18 L21.2525482,18 C21.6667618,18 22.0025482,18.3357864 22.0025482,18.75 C22.0025482,19.1296958 21.7203943,19.443491 21.3543188,19.4931534 L21.2525482,19.5 L2.75254822,19.5 C2.33833466,19.5 2.00254822,19.1642136 2.00254822,18.75 C2.00254822,18.3703042 2.2847021,18.056509 2.65077766,18.0068466 L2.75254822,18 L21.2525482,18 L2.75254822,18 Z M2.75254822,11.5030063 L21.2525482,11.5030063 C21.6667618,11.5030063 22.0025482,11.8387927 22.0025482,12.2530063 C22.0025482,12.6327021 21.7203943,12.9464972 21.3543188,12.9961597 L21.2525482,13.0030063 L2.75254822,13.0030063 C2.33833466,13.0030063 2.00254822,12.6672199 2.00254822,12.2530063 C2.00254822,11.8733105 2.2847021,11.5595153 2.65077766,11.5098529 L2.75254822,11.5030063 L21.2525482,11.5030063 L2.75254822,11.5030063 Z M2.75168905,5.0032392 L21.251689,5.0032392 C21.6659026,5.0032392 22.001689,5.33902564 22.001689,5.7532392 C22.001689,6.13293497 21.7195352,6.44673016 21.3534596,6.49639258 L21.251689,6.5032392 L2.75168905,6.5032392 C2.33747549,6.5032392 2.00168905,6.16745276 2.00168905,5.7532392 C2.00168905,5.37354343 2.28384293,5.05974824 2.64991849,5.01008582 L2.75168905,5.0032392 L21.251689,5.0032392 L2.75168905,5.0032392 Z" id="🎨-Color"></path>
        </g>
      </g>
    </svg>
  </div>
</header>
<nav class="mobile-nav hidden">
  <ul class="mobile-nav__list">
    <li><a class="mobile-nav__link" href="#">Home</a></li>
    <li><a class="mobile-nav__link" href="#">About</a></li>
    <li><a class="mobile-nav__link" href="#">Contact</a></li>
  </ul>
  <div class="mobile-nav__close">
    <svg xmlns="http://www.w3.org/2000/svg" width="24px" height="24px" x="0px" y="0px" viewBox="0 0 490 490" style="enable-background:new 0 0 490 490;" xml:space="preserve">
      <polygon fill="#ffffff" points="456.851,0 245,212.564 33.149,0 0.708,32.337 212.669,245.004 0.708,457.678 33.149,490 245,277.443 456.851,490 489.292,457.678 277.331,245.004 489.292,32.337 "/>
    </svg>
  </div>
</nav>
!

CSS 

              
                @import url('https://fonts.googleapis.com/css2?family=Open+Sans:ital,[email protected],400;0,700;1,400&display=swap');


:root {
    --header-height: 50px;
    --header-background: #2c2c2c;
    --header-hover: #414141;
}

* {
    box-sizing: border-box;
    list-style: none;
    margin: 0;
    padding: 0;
    text-decoration: none;
    text-transform: none;
}

html, body {
    min-height: 100vh;
    height: 100%;
    font-family: 'Open Sans', sans-serif;
    font-size: 16px;
}

.header {
    display: flex;
    width: 100%;
    padding: 0 10px;
    height: var(--header-height);
    background: var(--header-background);
}

.header__logo {
    display: flex;
    align-items: center;
    justify-content: center;
    padding: 0 10px;
    color: white;
    font-weight: bold;
    font-size: 1.3rem;
}

.logo__image {
    width: var(--header-height);
    padding: 10px;
}

.header__nav {
    display: flex;
}

.header__list {
    display: flex;
}

.header__link {
    display: flex;
    align-items: center;
    padding: 0 10px;
    height: var(--header-height);
    color: white;
}

.header__link:hover {
    background: var(--header-hover);
}

.burger {
    display: flex;
    justify-content: center;
    align-items: center;
    padding: 0 10px;
    cursor: pointer;
    margin-left: auto;
}

.mobile-nav {
    display: flex;
    position: fixed;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
    background: var(--header-background);
    transition: display 0.3s;
}

.mobile-nav__list {
    display: flex;
    flex-direction: column;
    align-items: center;
    justify-content: center;
    width: 100%;
}

.mobile-nav__link {
    display: flex;
    justify-content: center;
    padding: 10px 0;
    color: white;
    font-weight: bold;
}

.mobile-nav__close {
    display: flex;
    justify-content: center;
    align-items: center;
    position: fixed;
    bottom: 0;
    left: 0;
    width: 100%;
    background: #212121;
    height: var(--header-height);
    cursor: pointer;
}

/* tablet */
@media (max-width: 768px) {
    .header__nav { display: none; }
    .header { position: fixed; bottom: 0; left: 0; }
}

/* desktop */
@media (min-width: 769px) {
    .burger { display: none; }
}

.hidden {
    display: none;
}
!

JS 

              
                const burger = document.querySelector('.burger');
const mobileNavClose = document.querySelector('.mobile-nav__close');
const mobileNav = document.querySelector('.mobile-nav');

burger.addEventListener('click', (e) => {
    mobileNav.classList.toggle('hidden');
});
mobileNavClose.addEventListener('click', (e) => {
    mobileNav.classList.toggle('hidden');
});
!
999px

Console