/* RichReadme Blog - Modern Minimalist Design */
:root {
  --color-bg: #ffffff;
  --color-text: #1a1a1a;
  --color-text-secondary: #666666;
  --color-accent: #2563eb;
  --color-accent-hover: #1d4ed8;
  --color-border: #e5e7eb;
  --color-card: #f9fafb;
  --radius-sm: 6px;
  --radius-md: 10px;
  --radius-lg: 16px;
  --max-width: 720px;
}

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

body {
  font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, Oxygen, Ubuntu, sans-serif;
  background: var(--color-bg);
  color: var(--color-text);
  line-height: 1.7;
  font-size: 17px;
}

.container {
  max-width: var(--max-width);
  margin: 0 auto;
  padding: 0 24px;
}

/* Header */
.site-header {
  border-bottom: 1px solid var(--color-border);
  padding: 20px 0;
  margin-bottom: 48px;
}

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

.site-logo {
  font-size: 20px;
  font-weight: 700;
  color: var(--color-text);
  text-decoration: none;
}

.site-nav a {
  color: var(--color-text-secondary);
  text-decoration: none;
  margin-left: 24px;
  font-size: 15px;
}

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

/* Hero */
.hero {
  text-align: center;
  margin-bottom: 64px;
}

.hero h1 {
  font-size: 42px;
  font-weight: 800;
  line-height: 1.2;
  margin-bottom: 16px;
}

.hero p {
  font-size: 19px;
  color: var(--color-text-secondary);
  max-width: 560px;
  margin: 0 auto;
}

/* Book Grid */
.book-grid {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(300px, 1fr));
  gap: 24px;
  margin-bottom: 64px;
}

.book-card {
  border: 1px solid var(--color-border);
  border-radius: var(--radius-md);
  padding: 24px;
  transition: box-shadow 0.2s, transform 0.2s;
  text-decoration: none;
  color: inherit;
  display: block;
}

.book-card:hover {
  box-shadow: 0 4px 20px rgba(0,0,0,0.08);
  transform: translateY(-2px);
}

.book-card .category {
  font-size: 13px;
  color: var(--color-accent);
  font-weight: 600;
  text-transform: uppercase;
  letter-spacing: 0.5px;
  margin-bottom: 8px;
}

.book-card h3 {
  font-size: 20px;
  font-weight: 700;
  margin-bottom: 8px;
  line-height: 1.3;
}

.book-card .author {
  font-size: 14px;
  color: var(--color-text-secondary);
  margin-bottom: 12px;
}

.book-card .excerpt {
  font-size: 15px;
  color: var(--color-text-secondary);
  line-height: 1.6;
}

/* Article Page */
.article-header {
  margin-bottom: 40px;
}

.article-category {
  font-size: 13px;
  color: var(--color-accent);
  font-weight: 600;
  text-transform: uppercase;
  letter-spacing: 0.5px;
  margin-bottom: 12px;
}

.article-title {
  font-size: 36px;
  font-weight: 800;
  line-height: 1.2;
  margin-bottom: 12px;
}

.article-meta {
  font-size: 15px;
  color: var(--color-text-secondary);
}

/* Video Embed */
.video-container {
  position: relative;
  padding-bottom: 56.25%;
  height: 0;
  overflow: hidden;
  border-radius: var(--radius-md);
  margin-bottom: 40px;
}

.video-container iframe {
  position: absolute;
  top: 0;
  left: 0;
  width: 100%;
  height: 100%;
}

/* Article Content */
.article-content h2 {
  font-size: 26px;
  font-weight: 700;
  margin: 40px 0 16px;
}

.article-content p {
  margin-bottom: 20px;
}

.article-content ul {
  margin-bottom: 20px;
  padding-left: 24px;
}

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

.article-content blockquote {
  border-left: 4px solid var(--color-accent);
  padding-left: 20px;
  margin: 24px 0;
  font-style: italic;
  color: var(--color-text-secondary);
}

/* Article Figures (video frame captures) */
.article-figure {
  margin: 32px 0;
  border-radius: var(--radius-md);
  overflow: hidden;
  box-shadow: 0 8px 28px rgba(0, 0, 0, 0.18);
  border: 1px solid var(--color-border);
  background: #0a0f1a;
}

.article-figure img {
  display: block;
  width: 100%;
  height: auto;
}

.article-figure figcaption {
  font-size: 13px;
  color: var(--color-text-secondary);
  text-align: center;
  padding: 10px 16px;
  background: var(--color-card);
  border-top: 1px solid var(--color-border);
}

.lesson-heading {
  display: flex;
  align-items: center;
  gap: 12px;
  margin: 48px 0 20px;
  flex-wrap: wrap;
}

.lesson-heading .lesson-num {
  flex-shrink: 0;
  font-size: 12px;
  font-weight: 700;
  text-transform: uppercase;
  letter-spacing: 0.08em;
  color: #fff;
  background: var(--color-accent);
  padding: 5px 12px;
  border-radius: 100px;
}

.lesson-heading h2 {
  margin: 0 !important;
  font-size: 24px !important;
}

/* CTA Box */
.cta-box {
  background: var(--color-card);
  border-radius: var(--radius-md);
  padding: 24px;
  margin: 40px 0;
  text-align: center;
}

.cta-box p {
  margin-bottom: 16px;
  color: var(--color-text-secondary);
}

.cta-button {
  display: inline-block;
  background: var(--color-accent);
  color: white;
  padding: 12px 24px;
  border-radius: var(--radius-sm);
  text-decoration: none;
  font-weight: 600;
}

.cta-button:hover {
  background: var(--color-accent-hover);
}

/* Footer */
.site-footer {
  border-top: 1px solid var(--color-border);
  padding: 40px 0;
  margin-top: 80px;
  text-align: center;
  color: var(--color-text-secondary);
  font-size: 14px;
}

/* Responsive */
@media (max-width: 640px) {
  .hero h1 {
    font-size: 32px;
  }
  .article-title {
    font-size: 28px;
  }
  .book-grid {
    grid-template-columns: 1fr;
  }
}