body {
  margin: 0;
  font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, "Helvetica Neue", Arial, sans-serif;
  background: #f9f9f9;
  color: #333;
  scroll-behavior: smooth;
}

/* Hero部分（画面の上半分） */
.hero {
  height: 50vh; /* 半分に */
  background: linear-gradient(-45deg, #ff6b6b, #f5a623, #4facfe, #00f2fe);
  background-size: 400% 400%;
  animation: gradientBG 15s ease infinite;
  display: flex;
  align-items: center;
  justify-content: center;
  text-align: center;
  color: white;
}

@keyframes gradientBG {
  0% { background-position: 0% 50%; }
  50% { background-position: 100% 50%; }
  100% { background-position: 0% 50%; }
}

.hero .overlay {
  background: rgba(0,0,0,0.3);
  padding: 20px;
  border-radius: 12px;
}

nav a {
  color: #fff;
  margin: 0 10px;
  text-decoration: none;
  font-weight: bold;
}
nav a:hover {
  text-decoration: underline;
}

/* セクション（画面下半分以降） */
.section {
  max-width: 800px;
  margin: 40px auto;
  padding: 20px;
  background: #fff;
  border-radius: 12px;
  box-shadow: 0 5px 15px rgba(0,0,0,0.1);
}

.section a {
  color: #4facfe;
  text-decoration: none;
  font-weight: 600;
}

.section a:hover {
  text-decoration: underline;
}

h2 {
  color: #222;
  border-bottom: 2px solid #4facfe;
  display: inline-block;
  padding-bottom: 5px;
}

/* カード */
.cards {
  display: grid;
  gap: 20px;
  grid-template-columns: repeat(auto-fit, minmax(220px, 1fr));
}

.card {
  background: white;
  padding: 20px;
  border-radius: 12px;
  box-shadow: 0 5px 15px rgba(0,0,0,0.1);
  transition: transform 0.3s, box-shadow 0.3s;
}

.card:hover {
  transform: translateY(-8px);
  box-shadow: 0 8px 20px rgba(0,0,0,0.2);
}

/* フッター */
footer {
  text-align: center;
  padding: 30px 20px;
  margin-top: 40px;
  background: #fff;
  color: #666;
  border-top: 1px solid #e7e7e7;
}

/* アニメーション */
.fade-in {
  opacity: 0;
  animation: fadeIn 2s forwards;
}
.fade-in.delay {
  animation-delay: 1s;
}

.fade-in-up {
  opacity: 0;
  transform: translateY(20px);
  transition: all 0.8s ease;
}
.fade-in-up.visible {
  opacity: 1;
  transform: translateY(0);
}

@keyframes fadeIn {
  to { opacity: 1; }
}

/* Timeline */
.timeline {
  position: relative;
  margin-top: 30px;
  padding-left: 40px;
  border-left: 3px solid #4facfe;
}

.timeline-item {
  position: relative;
  margin-bottom: 30px;
}

.timeline-item:last-child {
  margin-bottom: 0;
}

.timeline-item::before {
  content: '';
  position: absolute;
  left: -49.5px;
  top: 5px;
  width: 16px;
  height: 16px;
  border-radius: 50%;
  background: #fff;
  border: 3px solid #4facfe;
  z-index: 1;
}

.timeline-year {
  font-weight: bold;
  font-size: 1.2em;
  color: #333;
  margin-bottom: 8px;
}

.timeline-content {
  padding: 15px;
  background: #f9f9f9;
  border-radius: 8px;
}

.timeline-content p {
  margin: 0 0 8px 0;
}

.timeline-content p:last-child {
  margin-bottom: 0;
}