:root {
  --bg: #f7f9f9;
  --card-bg: #ffffff;
  --text: #0f1419;
  --text-secondary: #536471;
  --border: #eff3f4;
  --accent: #1d9bf0;
  --accent-hover: #1a8cd8;
  --tag-bg: #e8f5fd;
  --tag-text: #1d9bf0;
  --shadow: 0 1px 3px rgba(0,0,0,0.04);
  --radius: 16px;
  --font: "Segoe UI", "Hiragino Sans", "Hiragino Kaku Gothic ProN", Meiryo, sans-serif;
  --font-mono: "Cascadia Code", "JetBrains Mono", "Source Code Pro", Consolas, monospace;
}

[data-theme="dark"] {
  --bg: #000000;
  --card-bg: #16181c;
  --text: #e7e9ea;
  --text-secondary: #71767b;
  --border: #2f3336;
  --accent: #1d9bf0;
  --accent-hover: #1a8cd8;
  --tag-bg: #1d2e40;
  --tag-text: #1d9bf0;
  --shadow: 0 1px 3px rgba(255,255,255,0.03);
}

@media (prefers-color-scheme: dark) {
  :root:not([data-theme="light"]) {
    --bg: #000000;
    --card-bg: #16181c;
    --text: #e7e9ea;
    --text-secondary: #71767b;
    --border: #2f3336;
    --accent: #1d9bf0;
    --accent-hover: #1a8cd8;
    --tag-bg: #1d2e40;
    --tag-text: #1d9bf0;
    --shadow: 0 1px 3px rgba(255,255,255,0.03);
  }
}

*, *::before, *::after { box-sizing: border-box; margin: 0; padding: 0; }

html { font-size: 16px; }
body {
  font-family: var(--font);
  background: var(--bg);
  color: var(--text);
  line-height: 1.75;
  min-height: 100vh;
  display: flex;
  flex-direction: column;
}

a { color: var(--accent); text-decoration: none; }
a:hover { text-decoration: underline; }

.site-header {
  position: sticky;
  top: 0;
  z-index: 100;
  background: var(--card-bg);
  border-bottom: 1px solid var(--border);
  backdrop-filter: blur(8px);
}

.header-inner {
  max-width: 640px;
  margin: 0 auto;
  padding: 0 16px;
  height: 52px;
  display: flex;
  align-items: center;
  justify-content: space-between;
}

.site-logo {
  font-size: 1.25rem;
  font-weight: 700;
  color: var(--text);
  letter-spacing: -0.02em;
}
.site-logo:hover { text-decoration: none; }

.site-nav {
  display: flex;
  align-items: center;
  gap: 16px;
  font-size: 0.875rem;
}
.site-nav a { color: var(--text-secondary); }
.site-nav a:hover { color: var(--text); text-decoration: none; }

.theme-toggle {
  width: 36px;
  height: 36px;
  border-radius: 50%;
  border: none;
  background: transparent;
  color: var(--text-secondary);
  cursor: pointer;
  font-size: 1.1rem;
  display: flex;
  align-items: center;
  justify-content: center;
  transition: background 0.15s;
}
.theme-toggle:hover { background: var(--border); }

.main-content {
  flex: 1;
  max-width: 640px;
  width: 100%;
  margin: 0 auto;
  padding: 24px 16px 48px;
}

.site-footer {
  text-align: center;
  padding: 24px 16px;
  font-size: 0.8rem;
  color: var(--text-secondary);
  border-top: 1px solid var(--border);
}

.timeline-title {
  font-size: 1.5rem;
  font-weight: 700;
  margin-bottom: 4px;
}

.timeline-desc {
  font-size: 0.9rem;
  color: var(--text-secondary);
  margin-bottom: 24px;
}

.timeline {
  display: flex;
  flex-direction: column;
  gap: 12px;
}

.post-card {
  background: var(--card-bg);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 20px;
  box-shadow: var(--shadow);
  transition: background 0.15s;
}
.post-card:hover { background: var(--border); }

.post-card-meta {
  display: flex;
  align-items: center;
  flex-wrap: wrap;
  gap: 8px;
  font-size: 0.8rem;
  color: var(--text-secondary);
  margin-bottom: 6px;
}

.post-card-title {
  font-size: 1.15rem;
  font-weight: 700;
  margin-bottom: 8px;
  line-height: 1.4;
}
.post-card-title a { color: var(--text); }
.post-card-title a:hover { text-decoration: underline; }

.post-card-body {
  font-size: 0.925rem;
  color: var(--text);
  line-height: 1.8;
  margin-bottom: 10px;
  max-height: 9em;
  overflow: hidden;
}

.post-card-body p { margin-bottom: 0.5em; }
.post-card-body p:last-child { margin-bottom: 0; }
.post-card-body code {
  font-family: var(--font-mono);
  font-size: 0.875em;
  background: var(--border);
  padding: 1px 5px;
  border-radius: 4px;
}

.post-card-link {
  font-size: 0.85rem;
  font-weight: 500;
}

.tag {
  display: inline-flex;
  align-items: center;
  padding: 1px 10px;
  border-radius: 999px;
  background: var(--tag-bg);
  color: var(--tag-text);
  font-size: 0.78rem;
  font-weight: 500;
  line-height: 1.7;
}
.tag:hover { text-decoration: none; filter: brightness(0.95); }

.empty-state {
  text-align: center;
  padding: 48px 16px;
  color: var(--text-secondary);
}

.post-header { margin-bottom: 24px; }

.post-title {
  font-size: 1.6rem;
  font-weight: 800;
  line-height: 1.35;
  margin-bottom: 8px;
  letter-spacing: -0.01em;
}

.post-meta {
  display: flex;
  align-items: center;
  flex-wrap: wrap;
  gap: 8px;
  font-size: 0.875rem;
  color: var(--text-secondary);
}

.post-body {
  font-size: 1rem;
  line-height: 2;
  margin-bottom: 32px;
}
.post-body p { margin-bottom: 1em; }
.post-body code {
  font-family: var(--font-mono);
  font-size: 0.875em;
  background: var(--border);
  padding: 2px 6px;
  border-radius: 4px;
}

.post-nav {
  display: flex;
  justify-content: space-between;
  gap: 16px;
  padding: 16px 0;
  border-top: 1px solid var(--border);
  border-bottom: 1px solid var(--border);
  margin-bottom: 32px;
  font-size: 0.9rem;
}
.post-nav-prev, .post-nav-next {
  max-width: 48%;
  overflow: hidden;
  text-overflow: ellipsis;
  white-space: nowrap;
}

.related-posts { margin-top: 8px; }

.related-title {
  font-size: 1.15rem;
  font-weight: 700;
  margin-bottom: 12px;
}

.related-grid {
  display: flex;
  flex-direction: column;
  gap: 10px;
}

.related-card {
  background: var(--card-bg);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 16px 20px;
  box-shadow: var(--shadow);
}
.related-card:hover { background: var(--border); }
.related-card time {
  font-size: 0.78rem;
  color: var(--text-secondary);
  display: block;
  margin-bottom: 2px;
}
.related-card h3 {
  font-size: 1rem;
  font-weight: 700;
  margin-bottom: 6px;
}
.related-card h3 a { color: var(--text); }
.related-tags { display: flex; flex-wrap: wrap; gap: 4px; }

.tag-title {
  font-size: 1.4rem;
  font-weight: 700;
  margin-bottom: 20px;
}
.tag-label { color: var(--accent); margin-right: 2px; }

.all-tags {
  margin-top: 40px;
  padding-top: 24px;
  border-top: 1px solid var(--border);
}
.all-tags h2 {
  font-size: 1.1rem;
  font-weight: 700;
  margin-bottom: 12px;
}

.tag-cloud {
  display: flex;
  flex-wrap: wrap;
  gap: 8px;
}

.tag-count {
  margin-left: 4px;
  opacity: 0.6;
  font-size: 0.75em;
}