header {
  position: fixed;
  top: 0;
  width: 100%;
  background: rgba(255, 255, 255, 0.95);
  backdrop-filter: blur(10px);
  z-index: 1000;
  transition: all 0.3s ease;
  display: none;
}

.header-container {
  max-width: 1200px;
  margin: 0 auto;
  padding: 1rem 2rem;
  display: flex;
  justify-content: space-between;
  align-items: center;
}

.logo {
  font-size: 1.8rem;
  font-weight: 700;
  color: #2563eb;
  text-decoration: none;
}

.nav-menu {
  display: flex;
  list-style: none;
  gap: 2rem;
  transition: all 0.3s;
}

.nav-menu a {
  text-decoration: none;
  color: #333;
  font-weight: 500;
  transition: color 0.3s ease;
  position: relative;
}

.nav-menu a:hover {
  color: #2563eb;
}

.nav-menu a::after {
  content: '';
  position: absolute;
  bottom: -5px;
  left: 0;
  width: 0;
  height: 2px;
  background: #2563eb;
  transition: width 0.3s ease;
}

.nav-menu a:hover::after {
  width: 100%;
}

.mobile-menu-btn {
  display: none;
  background: none;
  border: none;
  font-size: 2rem;
  cursor: pointer;
  color: #333;
  flex-direction: column;
  justify-content: center;
  align-items: center;
  width: 44px;
  height: 44px;
  z-index: 1101;
}
.mobile-menu-btn span {
  display: block;
  width: 100%;
  height: 3px;
  margin: 5px auto;
  background: #333;
  border-radius: 2px;
  transition: all 0.3s;
}

/* モバイル用 */
@media (max-width: 768px) {
  .nav-menu {
    position: fixed;
    top: 0;
    left: 0;
    width: 100vw;
    height: 100vh;
    background: rgba(255,255,255,0.98);
    flex-direction: column;
    justify-content: center;
    align-items: center;
    gap: 2.5rem;
    z-index: 1100;
    transform: translateY(-100%);
    opacity: 0;
    pointer-events: none;
  }
  .nav-menu.open {
    transform: translateY(0);
    opacity: 1;
    pointer-events: auto;
  }
  .mobile-menu-btn {
    display: flex;
  }
  /* ハンバーガーアイコンのアニメーション */
  .mobile-menu-btn.active span:nth-child(1) {
    transform: translateY(13px) rotate(45deg);
  }
  .mobile-menu-btn.active span:nth-child(2) {
    opacity: 0;
  }
  .mobile-menu-btn.active span:nth-child(3) {
    transform: translateY(-13px) rotate(-45deg);
  }
  /* PC時はnav-menuはflex */
  @media (min-width: 769px) {
    .nav-menu {
      position: static;
      flex-direction: row;
      height: auto;
      background: none;
      transform: none;
      opacity: 1;
      pointer-events: auto;
    }
    .mobile-menu-btn {
      display: none;
    }
  }
}