一階層ドロップダウン(ボタン)

デモ

See the Pen nav 14 by logsuke (@design-list) on CodePen.

コード

<!-- Boxicons headタグ内へ -->
<link href='https://unpkg.com/boxicons@2.1.2/css/boxicons.min.css' rel='stylesheet'>

    <header class="header" id="header">
        <nav class="nav">
            <a href="#" class="logo">
                <svg viewBox="0 0 496 512" width="100" title="meh-rolling-eyes">
                    <path
                        d="M248 8C111 8 0 119 0 256s111 248 248 248 248-111 248-248S385 8 248 8zM88 224c0-24.3 13.7-45.2 33.6-56-.7 2.6-1.6 5.2-1.6 8 0 17.7 14.3 32 32 32s32-14.3 32-32c0-2.8-.9-5.4-1.6-8 19.9 10.8 33.6 31.7 33.6 56 0 35.3-28.7 64-64 64s-64-28.7-64-64zm224 176H184c-21.2 0-21.2-32 0-32h128c21.2 0 21.2 32 0 32zm32-112c-35.3 0-64-28.7-64-64 0-24.3 13.7-45.2 33.6-56-.7 2.6-1.6 5.2-1.6 8 0 17.7 14.3 32 32 32s32-14.3 32-32c0-2.8-.9-5.4-1.6-8 19.9 10.8 33.6 31.7 33.6 56 0 35.3-28.7 64-64 64z" />
                </svg>
                logo
            </a>
            <div class="nav-menu" id="navMenu">
                <ul class="nav-links">
                    <li class="nav-item">
                        <button>Section1</button>
                        <ul class="drop-down">
                            <li><a href="#section1-1">Section1-1</a></li>
                            <li><a href="#section1-2">Section1-2</a></li>
                            <li><a href="#section1-3">Section1-3</a></li>
                            <li><a href="#section1-4">Section1-4</a></li>
                        </ul>
                    </li>
                    <li class="nav-item"><a href="#section2" class="nav-link">Section2</a></li>
                    <li class="nav-item">
                        <button>Section3</button>
                        <ul class="drop-down">
                            <li><a href="#section3-1">Section3-1</a></li>
                            <li><a href="#section3-2">Section3-2</a></li>
                            <li><a href="#section3-3">Section3-3</a></li>
                            <li><a href="#section3-4">Section3-4</a></li>
                        </ul>
                    </li>
                    <li class="nav-item"><a href="#section4" class="nav-link">Section4</a></li>
                </ul>
            </div>
        </nav>
    </header>

/*=== Base ===*/

* {
     margin: 0;
     padding: 0;
     box-sizing: border-box;
     font-family: sans-serif;
   }
   
   :root {
     --nav-height: 8rem;
     --max-width: 1024px;
     --container-padding: 0 4rem;
     --gap: 2rem;
     --bg-color: rgb(240, 240, 240);
   }
   
   /*=== Font ratio ===*/
   
   html {
     scroll-behavior: smooth;
     font-size: 62.5%;
   }
   
   body {
     font-size: 1.6rem;
   }
   
   ul {
     list-style: none;
   }
   
   a {
     text-decoration: none;
   }
   
   button {
     border: none;
     font-size: 1.6rem;
   }
   
   /* header */
   header {
     width: 100%;
     position: fixed;
     top: 0;
     left: 0;
     z-index: 100;
     background-color: var(--bg-color);
   }
   
   .nav svg {
     width: 25px;
     padding: 2px;
     margin-right: 5px;
   }
   
   /* nav */
   .nav {
     width: 100%;
     max-width: var(--max-width);
     height: var(--nav-height);
     display: flex;
     justify-content: space-between;
     align-items: center;
     margin: 0 auto;
     padding: 0 3rem;
   }
   
   .logo,
   .nav-toggle {
     color: var(--text-color);
     cursor: pointer;
   }
   
   .logo {
     font-weight: bold;
     font-size: 2rem;
     z-index: 100;
     display: flex;
     justify-content: center;
     align-items: center;
   }
   
   .nav-links {
     display: flex;
     align-items: center;
     justify-content: center;
     gap: 2rem;
   }
   
   .nav-links .nav-item {
     position: relative;
   }
   
   .nav-links a {
     color: var(--text-color);
     display: flex;
     justify-content: center;
     align-items: center;
     height: var(--nav-height);
   }
   
   .nav-links a:hover {
     color: rgb(134, 170, 207);
   }
   
   .nav-links a, .nav-links button {
     color: var(--text-color);
     display: flex;
     justify-content: center;
     align-items: center;
     height: var(--nav-height);
     border: none;
     font-size: 1.6rem;
     cursor: pointer;
   }
   
   .nav-links button:hover, .nav-links button:focus {
     color: rgb(134, 170, 207);
     outline:0;
   }
   
   .drop-down {
     position: absolute;
     top: var(--nav-height);
     left: 50%;
     transform: translateX(-50%);
     background: var(--bg-color);
     padding: .5rem 1rem;
     border-radius: 10px;
     opacity: 0;
     pointer-events: none;
     transition: transform .5s;
   }
   
   .nav-links button:focus+.drop-down {
     opacity: 1;
     pointer-events: auto;
     transform: translate(-50%, 15px);
   }
   
   .drop-down a {
     width: 180px;
   }