* {
  box-sizing: border-box;
}

body {
  font-family: 'Noto Sans JP', -apple-system, BlinkMacSystemFont, 'Segoe UI', sans-serif;
  line-height: 1.8;
  color: #333;
  background-color: #f5f7fa;
  margin: 0;
  padding: 0;
}

a {
  text-decoration: none;
  color: #333;
}

.container {
  max-width: 1200px;
  margin: 0 auto;
  padding: 0 20px;
}

header {
  background-color: #fff;
  padding: 20px 0;
  border-bottom: 1px solid #e1e8ed;
  position: sticky;
  top: 0;
  z-index: 1000;
  box-shadow: 0 2px 4px rgba(0,0,0,0.05);
}

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

.logo a {
  font-size: 20px;
  font-weight: bold;
  color: #2c5282;
  transition: color 0.3s;
}

.logo a:hover {
  color: #1a365d;
}

.hamburger {
  display: none;
  flex-direction: column;
  cursor: pointer;
}

.hamburger span {
  width: 25px;
  height: 3px;
  background-color: #333;
  margin: 3px 0;
  transition: 0.3s;
}

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

nav li {
  margin-left: 30px;
}

nav a {
  font-weight: 500;
  transition: color 0.3s;
  color: #555;
  font-size: 15px;
}

nav a:hover {
  color: #2c5282;
}

footer {
  background-color: #263238;
  color: #fff;
  text-align: center;
  padding: 2rem 0;
  margin-top: 4rem;
}

footer .container {
  max-width: 1200px;
  margin: 0 auto;
  padding: 0 20px;
}

footer .footer-links {
  margin-bottom: 1rem;
}

footer .footer-links a {
  color: #fff;
  margin: 0 1rem;
  font-size: 14px;
  transition: opacity 0.3s;
}

footer .footer-links a:hover {
  opacity: 0.8;
}

footer p {
  margin: 1rem 0;
  font-size: 14px;
}

footer .social-links a {
  color: #fff;
  margin: 0 0.5rem;
  font-size: 14px;
  transition: opacity 0.3s;
}

footer .social-links a:hover {
  opacity: 0.8;
}

.blog-list-header {
  text-align: center;
  padding: 3rem 0 2rem;
}

.blog-list-header h1 {
  font-size: 2.5rem;
  color: #263238;
  margin-bottom: 1rem;
}

.blog-list-header p {
  font-size: 1.1rem;
  color: #546e7a;
  max-width: 700px;
  margin: 0 auto;
}

.blog-list {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(300px, 1fr));
  gap: 2rem;
  padding: 2rem 0;
}

.blog-card {
  background: #fff;
  border-radius: 12px;
  overflow: hidden;
  box-shadow: 0 4px 12px rgba(0,0,0,0.08);
  transition: transform 0.3s, box-shadow 0.3s;
}

.blog-card:hover {
  transform: translateY(-4px);
  box-shadow: 0 8px 24px rgba(0,0,0,0.12);
}

.blog-thumbnail {
  width: 100%;
  height: 200px;
  object-fit: cover;
  display: block;
}

.blog-card-content {
  padding: 1.5rem;
}

.blog-card-content h2 {
  font-size: 1.3rem;
  margin: 0 0 0.5rem;
  line-height: 1.4;
}

.blog-card-content h2 a {
  color: #263238;
  transition: color 0.3s;
}

.blog-card-content h2 a:hover {
  color: #2c5282;
}

.blog-card-content time {
  display: block;
  font-size: 0.9rem;
  color: #78909c;
  margin-bottom: 0.75rem;
}

.article-summary {
  font-size: 0.95rem;
  line-height: 1.7;
  color: #546e7a;
  margin: 1rem 0;
}

.read-more {
  display: inline-block;
  color: #2c5282;
  font-weight: 600;
  margin-top: 0.5rem;
  transition: color 0.3s;
}

.read-more:hover {
  color: #1a365d;
}

/* 2カラムレイアウト */
.blog-container {
  max-width: 1200px;
  margin: 2rem auto;
  padding: 0 20px;
  display: flex;
  gap: 2rem;
  align-items: flex-start;
}

.main-content {
  flex: 1;
  min-width: 0;
}

.sidebar {
  width: 300px;
  flex-shrink: 0;
}

.blog-main-content {
  background: #fff;
  border-radius: 12px;
  padding: 3rem;
  box-shadow: 0 4px 12px rgba(0,0,0,0.08);
}

.blog-header h1 {
  font-size: 2.2rem;
  color: #263238;
  line-height: 1.4;
  margin: 0 0 1rem;
}

.post-meta {
  border-bottom: 2px solid #e1e8ed;
  padding-bottom: 1rem;
  margin-bottom: 2rem;
}

.post-meta time {
  font-size: 0.95rem;
  color: #78909c;
}

.blog-hero-image {
  margin-bottom: 2.5rem;
  border-radius: 8px;
  overflow: hidden;
}

.blog-hero-image img {
  width: 100%;
  max-width: 100%;
  height: auto;
  display: block;
}

.blog-content h2 {
  font-size: 1.8rem;
  color: #263238;
  margin: 2.5rem 0 1rem;
  padding-bottom: 0.5rem;
  border-bottom: 3px solid #2c5282;
}

.blog-content h3 {
  font-size: 1.3rem;
  color: #37474f;
  margin: 1.5rem 0 0.75rem;
}

.blog-content p {
  margin: 1rem 0;
  line-height: 1.9;
  color: #455a64;
}

.blog-content ul,
.blog-content ol {
  margin: 1rem 0;
  padding-left: 2rem;
}

.blog-content li {
  margin: 0.5rem 0;
  line-height: 1.8;
  color: #455a64;
}

.blog-content img {
  max-width: 100%;
  height: auto;
  display: block;
  margin: 1.5rem auto;
  border-radius: 8px;
}

.tip-box {
  background: linear-gradient(135deg, #e3f2fd 0%, #f3e5f5 100%);
  border-left: 4px solid #2c5282;
  border-radius: 8px;
  padding: 1.5rem;
  margin: 2rem 0;
}

.tip-box h3 {
  font-size: 1.2rem;
  color: #1565c0;
  margin: 0 0 1rem;
}

.tip-box ul {
  margin: 0;
  padding-left: 1.5rem;
}

.tip-box li {
  color: #37474f;
}

.summary-box {
  background: linear-gradient(135deg, #fff3e0 0%, #ffe0b2 100%);
  border-left: 4px solid #ff9800;
  border-radius: 8px;
  padding: 1.5rem;
  margin: 2rem 0;
}

.summary-box h3 {
  font-size: 1.2rem;
  color: #e65100;
  margin: 0 0 1rem;
}

.summary-box ol {
  margin: 0;
  padding-left: 1.5rem;
}

.summary-box li {
  color: #37474f;
  font-weight: 500;
}

/* サイドバー */
.sidebar-section {
  background: #fff;
  border-radius: 12px;
  padding: 1.5rem;
  margin-bottom: 1.5rem;
  box-shadow: 0 4px 12px rgba(0,0,0,0.08);
}

.sidebar-section h3 {
  font-size: 1.1rem;
  color: #263238;
  margin: 0 0 1rem;
  padding-bottom: 0.5rem;
  border-bottom: 2px solid #2c5282;
}

.table-of-contents ul {
  list-style: none;
  padding: 0;
  margin: 0;
}

.table-of-contents li {
  margin: 0.5rem 0;
}

.table-of-contents a {
  color: #546e7a;
  font-size: 0.9rem;
  transition: color 0.3s;
  display: block;
  padding: 0.25rem 0;
}

.table-of-contents a:hover {
  color: #2c5282;
}

.ad-space {
  background: #f8f9fa;
  border: 2px dashed #dee2e6;
  border-radius: 8px;
  padding: 3rem 1rem;
  text-align: center;
  color: #6c757d;
  font-size: 0.9rem;
}

/* シェアボタン */
.share-buttons {
  margin: 2rem 0;
  padding: 1.5rem;
  background: #f8f9fa;
  border-radius: 8px;
  text-align: center;
}

.share-buttons h3 {
  font-size: 1rem;
  color: #263238;
  margin: 0 0 1rem;
}

.share-buttons a {
  display: inline-block;
  margin: 0 0.5rem;
  padding: 0.75rem 1.5rem;
  border-radius: 6px;
  color: #fff;
  font-weight: 600;
  transition: opacity 0.3s;
  font-size: 0.9rem;
}

.share-buttons a:hover {
  opacity: 0.8;
}

.share-buttons .twitter-share {
  background-color: #1da1f2;
}

.share-buttons .facebook-share {
  background-color: #1877f2;
}

.blog-back-link {
  margin-top: 3rem;
  padding-top: 2rem;
  border-top: 1px solid #e1e8ed;
}

.blog-back-link a {
  color: #2c5282;
  font-weight: 600;
  transition: color 0.3s;
}

.blog-back-link a:hover {
  color: #1a365d;
}

/* パンくずリスト */
.breadcrumbs {
  background-color: #fff;
  padding: 1rem 0;
  border-bottom: 1px solid #e1e8ed;
  font-size: 0.9rem;
}

.breadcrumbs a {
  color: #2c5282;
  transition: color 0.3s;
}

.breadcrumbs a:hover {
  color: #1a365d;
}

.breadcrumbs span {
  color: #78909c;
}

/* レスポンシブ対応 */
@media (max-width: 768px) {
  .hamburger {
    display: flex;
  }

  nav {
    display: none;
  }

  nav.active {
    display: block;
    position: absolute;
    top: 100%;
    left: 0;
    right: 0;
    background: #fff;
    box-shadow: 0 4px 8px rgba(0,0,0,0.1);
  }

  nav.active ul {
    flex-direction: column;
  }

  nav.active li {
    margin: 0;
    border-bottom: 1px solid #e1e8ed;
  }

  nav.active a {
    display: block;
    padding: 1rem 20px;
  }

  .blog-list-header h1 {
    font-size: 2rem;
  }

  .blog-list {
    grid-template-columns: 1fr;
  }

  .blog-container {
    flex-direction: column;
  }

  .sidebar {
    width: 100%;
    order: -1;
  }

  .blog-main-content {
    padding: 1.5rem;
  }

  .blog-header h1 {
    font-size: 1.6rem;
  }

  .blog-content h2 {
    font-size: 1.5rem;
  }

  .blog-content h3 {
    font-size: 1.2rem;
  }

  .share-buttons a {
    display: block;
    margin: 0.5rem 0;
  }
}