.site-header {
  position: fixed;
  top: 0;
  left: 0;
  width: 100%;
  height: 70px;
  background: white;
  box-shadow: 0 2px 10px rgba(0,0,0,0.1);
  z-index: 1000;          /* 他の要素より必ず上に来る */
}

.site-header .container {
  max-width: 1200px;
  margin: 0 auto;
  padding: 0 20px;
  height: 100%;
  display: flex;
  justify-content: space-between;
  align-items: center;
}

.logo a {
  font-size: 1.6rem;
  font-weight: bold;
  color: #333;
  text-decoration: none;
}

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

.main-nav li {
  margin-left: 2.2rem;
}

.main-nav a {
  color: #333;
  text-decoration: none;
  font-weight: 500;
  transition: color 0.2s;
}

.main-nav a:hover {
  color: #0066cc;
}