.header {
  background-color: var(--white-color);
  box-shadow: 0 2px 4px rgba(0, 0, 0, 0.05);
  position: sticky;
  top: 0;
  z-index: 1000;
  width: 100%;
}

.header .container {
  display: flex;
  justify-content: space-between;
  align-items: center;
  height: 70px;
}

.logo {
  font-family: var(--jp-sans);
  font-size: 1rem;
  font-weight: 700;
  color: var(--primary-color);
  text-decoration: none;
  margin-left: 0.5rem;
}

.logo:hover {
  color: var(--primary-color);
}

.nav ul {
  display: flex;
  list-style: none;
  margin: 0;
  padding: 0;
  gap: 2rem;
}

.nav a {
  font-family: var(--jp-sans);
  font-weight: 700;
  font-size: 0.9rem;
  color: var(--secondary-color);
  position: relative;
  padding: 5px 0;
  text-decoration: none;
}

.nav a::after {
  content: "";
  position: absolute;
  width: 100%;
  transform: scaleX(0);
  height: 2px;
  bottom: 0;
  left: 0;
  background-color: var(--accent-color-1);
  transform-origin: bottom right;
  transition: transform 0.25s ease-out;
}

.nav a:hover::after {
  transform: scaleX(1);
  transform-origin: bottom left;
}

.nav a:hover {
  color: var(--primary-color);
}

.menuToggle {
  display: none;
  background: none;
  border: none;
  color: var(--primary-color);
  cursor: pointer;
  padding: 0.5rem;
}

.menuToggle svg {
  width: 24px;
  height: 24px;
}

.menuToggle .close-icon {
  display: none;
}

.menuToggle .hamburger-icon {
  display: block;
}

.nav.navOpen ~ .menuToggle .close-icon {
  display: block;
}

.nav.navOpen ~ .menuToggle .hamburger-icon {
  display: none;
}

/* オーバーレイスタイル */
.navOverlay {
  position: fixed;
  top: 0;
  left: 0;
  width: 100%;
  height: 100%;
  background-color: rgba(44, 62, 80, 0.8);
  z-index: 998;
  opacity: 0;
  visibility: hidden;
  transition: opacity 0.3s ease, visibility 0.3s ease;
}

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

@media (max-width: 992px) {
  .header {
    position: fixed;
    top: 0;
    left: 0;
    right: 0;
    z-index: 1000;
  }
  
  .header.transparent {
    background-color: transparent;
    box-shadow: none;
  }
  
  .header.transparent .logo,
  .header.transparent .menuToggle {
    color: white;
  }
  
  /* 記事一覧ページでは透明化しない */
  .header:not(.transparent) {
    background-color: var(--white-color);
    box-shadow: 0 2px 4px rgba(0, 0, 0, 0.05);
  }
  
  .header:not(.transparent) .logo,
  .header:not(.transparent) .menuToggle {
    color: var(--primary-color);
  }
  
  .nav {
    position: absolute;
    top: 70px;
    left: 0;
    width: 100%;
    background-color: var(--white-color);
    flex-direction: column;
    transform: translateY(-150%);
    transition: transform 0.3s ease-in-out;
    box-shadow: 0 2px 4px rgba(0, 0, 0, 0.05);
    z-index: 999;
  }
  
  .nav.navOpen {
    transform: translateY(0);
  }
  
  .nav ul {
    flex-direction: column;
    width: 100%;
    padding: 1rem 0;
    gap: 0;
  }
  
  .nav li {
    text-align: center;
  }
  
  .nav a {
    display: block;
    padding: 1rem;
    width: 100%;
  }
  
  .nav a::after {
    display: none;
  }
  
  .menuToggle {
    display: block;
  }
}