:root {
  --color-primary: #1e3a5f;
  --color-primary-hover: #2c5282;
  --color-accent: #f5a623;
  --color-bg: #ffffff;
  --color-bg-alt: #fafafa;
  --color-text: #1a1a1a;
  --color-text-muted: #666666;
  --color-border: #e0e0e0;
  --color-code-bg: #f4f4f6;

  --font-sans: "Inter", "Hiragino Sans", "Yu Gothic UI", "Meiryo", sans-serif;
  --font-mono: "SF Mono", "Consolas", "Roboto Mono", "Source Code Pro", monospace;

  --max-width: 760px;
  --radius: 6px;
}

* {
  box-sizing: border-box;
}

html {
  scroll-behavior: smooth;
}

body {
  font-family: var(--font-sans);
  color: var(--color-text);
  background: var(--color-bg);
  margin: 0;
  line-height: 1.75;
  font-size: 16px;
  -webkit-font-smoothing: antialiased;
}

/* Header */
.site-header {
  border-bottom: 1px solid var(--color-border);
  background: var(--color-bg);
  position: sticky;
  top: 0;
  z-index: 10;
}

.site-header .container {
  max-width: var(--max-width);
  margin: 0 auto;
  padding: 16px 24px;
  display: flex;
  align-items: center;
  justify-content: space-between;
}

.site-logo {
  font-weight: 700;
  font-size: 1.3rem;
  color: var(--color-primary);
  text-decoration: none;
  letter-spacing: -0.02em;
}

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

.site-nav {
  display: flex;
  gap: 24px;
}

.site-nav a {
  color: var(--color-text);
  text-decoration: none;
  font-size: 0.95rem;
}

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

/* Main */
main {
  max-width: var(--max-width);
  margin: 0 auto;
  padding: 56px 24px;
}

.hero {
  margin-bottom: 56px;
}

.hero h1 {
  font-size: 2.4rem;
  margin: 0 0 16px;
  letter-spacing: -0.025em;
  color: var(--color-primary);
  line-height: 1.25;
}

.hero p {
  font-size: 1.1rem;
  color: var(--color-text-muted);
  margin: 0;
}

/* Headings */
h1, h2, h3, h4 {
  letter-spacing: -0.01em;
  line-height: 1.35;
  color: var(--color-text);
}

h2 {
  font-size: 1.6rem;
  margin: 56px 0 16px;
  padding-bottom: 8px;
  border-bottom: 2px solid var(--color-border);
}

h3 {
  font-size: 1.25rem;
  margin: 32px 0 12px;
}

p {
  margin: 0 0 16px;
}

a {
  color: var(--color-primary);
  text-decoration: underline;
  text-decoration-color: var(--color-border);
  text-underline-offset: 3px;
  transition: color 0.15s, text-decoration-color 0.15s;
}

a:hover {
  color: var(--color-primary-hover);
  text-decoration-color: var(--color-primary-hover);
}

/* Code */
code {
  font-family: var(--font-mono);
  font-size: 0.9em;
  background: var(--color-code-bg);
  padding: 2px 6px;
  border-radius: 3px;
}

pre {
  background: var(--color-code-bg);
  padding: 16px;
  border-radius: var(--radius);
  overflow-x: auto;
  border: 1px solid var(--color-border);
  font-size: 0.9rem;
  line-height: 1.6;
}

pre code {
  background: none;
  padding: 0;
  font-size: 1em;
}

blockquote {
  border-left: 4px solid var(--color-accent);
  margin: 24px 0;
  padding: 12px 20px;
  color: var(--color-text-muted);
  background: var(--color-bg-alt);
  border-radius: 0 var(--radius) var(--radius) 0;
}

blockquote p:last-child {
  margin-bottom: 0;
}

/* Article list (top page) */
.article-list {
  list-style: none;
  padding: 0;
  margin: 0;
}

.article-list li {
  padding: 24px 0;
  border-bottom: 1px solid var(--color-border);
}

.article-list li:last-child {
  border-bottom: none;
}

.article-meta {
  font-size: 0.85rem;
  color: var(--color-text-muted);
  margin-bottom: 6px;
  display: flex;
  gap: 12px;
  align-items: center;
}

.article-meta .category {
  background: var(--color-primary);
  color: white;
  padding: 2px 8px;
  border-radius: 3px;
  font-size: 0.75rem;
  font-weight: 600;
}

.article-title {
  font-size: 1.2rem;
  font-weight: 600;
  margin: 0 0 8px;
  line-height: 1.4;
}

.article-title a {
  color: var(--color-text);
  text-decoration: none;
}

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

.article-summary {
  color: var(--color-text-muted);
  margin: 0;
  font-size: 0.95rem;
}

/* Placeholder */
.placeholder {
  color: var(--color-text-muted);
  font-style: italic;
  padding: 48px 24px;
  text-align: center;
  background: var(--color-bg-alt);
  border-radius: var(--radius);
  border: 1px dashed var(--color-border);
}

/* Footer */
.site-footer {
  border-top: 1px solid var(--color-border);
  margin-top: 96px;
  padding: 32px 24px;
  text-align: center;
  font-size: 0.9rem;
  color: var(--color-text-muted);
  background: var(--color-bg-alt);
}

.site-footer .container {
  max-width: var(--max-width);
  margin: 0 auto;
}

.site-footer p {
  margin: 4px 0;
}

.site-footer a {
  color: var(--color-text-muted);
}

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

/* Article page */
.article-header {
  margin-bottom: 48px;
  padding-bottom: 24px;
  border-bottom: 1px solid var(--color-border);
}

.article-header .article-meta {
  margin-bottom: 12px;
}

.article-header h1 {
  font-size: 2rem;
  margin: 0 0 16px;
  letter-spacing: -0.025em;
  color: var(--color-primary);
  line-height: 1.35;
}

.article-lead {
  font-size: 1.1rem;
  color: var(--color-text-muted);
  margin: 0;
  line-height: 1.7;
}

.article-body h2 {
  margin-top: 56px;
}

.article-body h3 {
  margin-top: 36px;
}

.article-body ul,
.article-body ol {
  padding-left: 28px;
  margin: 16px 0;
}

.article-body li {
  margin-bottom: 8px;
}

.article-body strong {
  color: var(--color-text);
  font-weight: 700;
}

.article-related {
  margin-top: 64px;
  padding: 24px 28px;
  background: var(--color-bg-alt);
  border-radius: var(--radius);
  border-left: 4px solid var(--color-accent);
}

.article-related h3 {
  margin: 0 0 12px;
  font-size: 1.05rem;
}

.article-related ul {
  margin: 0;
  padding-left: 20px;
}

.article-related li {
  margin-bottom: 6px;
}

/* Responsive */
@media (max-width: 600px) {
  .site-header .container {
    flex-direction: column;
    gap: 12px;
    align-items: flex-start;
  }
  .site-nav {
    gap: 16px;
  }
  .hero h1 {
    font-size: 1.85rem;
  }
  main {
    padding: 32px 20px;
  }
  h2 {
    font-size: 1.4rem;
  }
}