ハンバーガーメニュー：モダン（オーバーレイ）｜Hamburger Menu: Modern Overlay

<div class="container">
  <div class="hamburger-menu">
    <div class="line"></div>
    <div class="line"></div>
    <div class="line"></div>
  </div>
  <div class="overlay"></div>
  <nav class="nav-menu">
    <a href="#">Menu 1</a>
    <a href="#">Menu 2</a>
    <a href="#">Menu 3</a>
    <a href="#">Menu 4</a>
    <a href="#">Menu 5</a>
    <a href="#">Menu 6</a>
    <a href="#">Menu 7</a>
    <a href="#">Menu 8</a>
    <a href="#">Menu 9</a>
    <a href="#">Menu 10</a>
  </nav>
</div>

.container {
  position: relative;
  width: 100%;
  height: 300px;
  background: #eef1ff;
}

.hamburger-menu {
  width: 30px;
  height: 22px;
  position: absolute;
  top: 20px;
  right: 20px;
  cursor: pointer;
  user-select: none;
  z-index: 1001;
}

.hamburger-menu .line {
  background-color: #fff;
  height: 4px;
  width: 100%;
  position: absolute;
  transition: all 0.3s;
  box-shadow: 0 1px 2px rgba(0,0,0,0.2);
}

.hamburger-menu .line:nth-of-type(1) {
  top: 0;
}

.hamburger-menu .line:nth-of-type(2) {
  top: 50%;
  transform:
  translateY(-50%);
}

.hamburger-menu .line:nth-of-type(3) {
  bottom: 0;
}

.hamburger-menu.active > .line:nth-of-type(1) {
  top: 50%;
  transform: translateY(-50%) rotate(45deg);
}

.hamburger-menu.active > .line:nth-of-type(2) {
  display: none;
}

.hamburger-menu.active > .line:nth-of-type(3) {
  top: 50%;
  transform: translateY(-50%) rotate(-45deg);
}

.overlay {
  position: absolute;
  top: 0;
  left: 0;
  width: 100%;
  height: 100%;
  background: linear-gradient(135deg, rgba(102, 126, 234, 0.2), rgba(118, 75, 162, 0.2));
  opacity: 0;
  visibility: hidden;
  transition: all 0.4s ease;
  z-index: 999;
}

.overlay.active {
  opacity: 1;
  visibility: visible;
}

@keyframes fadeIn {
  0% {
    top: 45%;
    opacity: 0;
  }

  100% {
    top: 50%;
    opacity: 1;
  }
}

.nav-menu {
  display: none;
  flex-direction: column;
  position: absolute;
  top: 50%;
  left: 50%;
  transform: translate(-50%, -50%);
  align-items: center;
  justify-content: flex-start;
  padding: 15px;
  width: 350px;
  background: linear-gradient(135deg, #667eea 0%, #764ba2 100%);
  border-radius: 20px;
  box-shadow: 0 15px 40px rgba(0,0,0,0.4);
  opacity: 0;
  z-index: 1000;
  max-height: 80%;
  overflow-y: auto;
}

.nav-menu.active {
  display: flex;
  animation: fadeIn 0.6s forwards;
}

.nav-menu a {
  text-decoration: none;
  color: white;
  padding: 15px 25px;
  margin: 8px;
  border-radius: 25px;
  transition: all 0.3s;
  font-weight: 500;
  opacity: 0;
  transform: translateY(-20px);
  pointer-events: none;
}

.nav-menu a.show {
  opacity: 1;
  transform: translateY(0);
  pointer-events: auto;
}

.nav-menu a:hover {
  background: rgba(255,255,255,0.2);
  transform: translateX(10px);
}

document.querySelectorAll('.hamburger-menu').forEach(hamburgerMenu => {
  const container = hamburgerMenu.parentElement;
  const navMenu = container.querySelector('.nav-menu');
  const overlay = container.querySelector('.overlay');

  hamburgerMenu.addEventListener('click', () => {
    hamburgerMenu.classList.toggle('active');
    navMenu.classList.toggle('active');

    if (navMenu.classList.contains('active')) {
      overlay.classList.add('active');
      setTimeout(() => {
        const menuItems = navMenu.querySelectorAll('a');
        menuItems.forEach((item, index) => {
          setTimeout(() => { item.classList.add('show'); }, index * 150);
        });
      }, 300);
    } else {
      const menuItems = navMenu.querySelectorAll('a');
      menuItems.forEach(item => item.classList.remove('show'));
      setTimeout(() => { overlay.classList.remove('active'); }, 200);
    }
  });
});