/* ============================================
   VLM Book — vlmbook.com
   ============================================ */

/* ---------- Reset & Base ---------- */
*,
*::before,
*::after {
  box-sizing: border-box;
  margin: 0;
  padding: 0;
}

:root {
  --color-bg: #ffffff;
  --color-text: #24292f;
  --color-text-secondary: #57606a;
  --color-accent: #4f46e5;
  --color-accent-hover: #4338ca;
  --color-surface: #f6f8fa;
  --color-border: #d0d7de;
  --color-heading: #1b1f24;
  --max-width: 960px;
  --font-sans: -apple-system, BlinkMacSystemFont, "Segoe UI", Helvetica, Arial, sans-serif, "Apple Color Emoji", "Segoe UI Emoji";
  --font-mono: "SFMono-Regular", Consolas, "Liberation Mono", Menlo, monospace;
}

html {
  scroll-behavior: smooth;
}

body {
  font-family: var(--font-sans);
  font-size: 17px;
  line-height: 1.7;
  color: var(--color-text);
  background: var(--color-bg);
  -webkit-font-smoothing: antialiased;
}

a {
  color: var(--color-accent);
  text-decoration: none;
  transition: color 0.15s ease;
}

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

img {
  max-width: 100%;
  height: auto;
}

/* ---------- Layout ---------- */
.wrapper {
  max-width: var(--max-width);
  margin: 0 auto;
  padding: 0 24px;
}

/* ---------- Header ---------- */
.site-header {
  border-top: 4px solid var(--color-accent);
  padding: 18px 0;
  background: var(--color-bg);
  position: sticky;
  top: 0;
  z-index: 100;
  backdrop-filter: blur(12px);
  background: rgba(255, 255, 255, 0.92);
}

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

.site-title {
  font-size: 18px;
  font-weight: 700;
  color: var(--color-heading);
  letter-spacing: -0.01em;
}

.site-title:hover {
  color: var(--color-accent);
  text-decoration: none;
}

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

.site-nav a {
  font-size: 14px;
  font-weight: 500;
  color: var(--color-text-secondary);
}

.site-nav a:hover {
  color: var(--color-accent);
  text-decoration: none;
}

/* ---------- Hero ---------- */
.hero {
  padding: 64px 0 56px;
}

.hero-inner {
  display: grid;
  grid-template-columns: 280px 1fr;
  gap: 48px;
  align-items: start;
}

.hero-cover {
  width: 100%;
  border-radius: 8px;
  box-shadow: 0 8px 30px rgba(0, 0, 0, 0.12), 0 2px 8px rgba(0, 0, 0, 0.08);
  transition: transform 0.2s ease, box-shadow 0.2s ease;
}

.hero-cover:hover {
  transform: translateY(-4px);
  box-shadow: 0 12px 40px rgba(0, 0, 0, 0.16), 0 4px 12px rgba(0, 0, 0, 0.1);
}

.hero-content h1 {
  font-size: 36px;
  font-weight: 800;
  line-height: 1.2;
  color: var(--color-heading);
  letter-spacing: -0.02em;
  margin-bottom: 8px;
}

.hero-subtitle {
  font-size: 18px;
  color: var(--color-text-secondary);
  margin-bottom: 24px;
  line-height: 1.5;
}

.hero-authors {
  font-size: 15px;
  color: var(--color-text-secondary);
  margin-bottom: 28px;
}

.hero-authors a {
  color: var(--color-text);
  font-weight: 600;
}

.hero-buttons {
  display: flex;
  flex-wrap: wrap;
  gap: 12px;
  margin-bottom: 0;
}

.hero-print-notice {
  margin-top: 20px;
  font-size: 15px;
  color: var(--color-text-secondary);
}

.hero-print-notice a {
  color: #d97706;
  font-weight: 600;
}

.hero-print-notice a:hover {
  color: #b45309;
}

/* ---------- Buttons ---------- */
.btn {
  display: inline-flex;
  align-items: center;
  gap: 8px;
  padding: 10px 20px;
  font-size: 14px;
  font-weight: 600;
  border-radius: 8px;
  border: 1px solid var(--color-border);
  background: var(--color-bg);
  color: var(--color-text);
  cursor: pointer;
  transition: all 0.15s ease;
  white-space: nowrap;
}

.btn:hover {
  text-decoration: none;
  border-color: var(--color-accent);
  color: var(--color-accent);
  box-shadow: 0 1px 3px rgba(79, 70, 229, 0.1);
}

.btn-primary {
  background: var(--color-accent);
  color: #fff;
  border-color: var(--color-accent);
}

.btn-primary:hover {
  background: var(--color-accent-hover);
  border-color: var(--color-accent-hover);
  color: #fff;
  box-shadow: 0 2px 8px rgba(79, 70, 229, 0.3);
}

.btn svg,
.btn i {
  font-size: 16px;
  width: 16px;
  height: 16px;
}

/* ---------- Sections ---------- */
section {
  padding: 56px 0;
}

section + section {
  border-top: 1px solid var(--color-border);
}

.section-title {
  font-size: 26px;
  font-weight: 700;
  color: var(--color-heading);
  letter-spacing: -0.01em;
  margin-bottom: 24px;
}

/* ---------- About ---------- */
.about-text p {
  margin-bottom: 16px;
  color: var(--color-text);
}

.about-text p:last-child {
  margin-bottom: 0;
}

/* ---------- Audience ---------- */
.audience-grid {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: 20px;
  margin-top: 20px;
}

.audience-card {
  background: var(--color-surface);
  border-radius: 10px;
  padding: 24px;
  border: 1px solid var(--color-border);
}

.audience-card .card-icon {
  font-size: 28px;
  margin-bottom: 12px;
  display: block;
}

.audience-card h3 {
  font-size: 16px;
  font-weight: 700;
  color: var(--color-heading);
  margin-bottom: 8px;
}

.audience-card p {
  font-size: 14px;
  color: var(--color-text-secondary);
  line-height: 1.6;
}

/* ---------- Chapters ---------- */
.chapters-list {
  list-style: none;
  counter-reset: chapter-counter;
}

.chapters-list li {
  counter-increment: chapter-counter;
  display: grid;
  grid-template-columns: 48px 1fr;
  gap: 16px;
  padding: 20px 0;
  border-bottom: 1px solid var(--color-border);
  align-items: start;
}

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

.chapter-number {
  display: flex;
  align-items: center;
  justify-content: center;
  width: 40px;
  height: 40px;
  border-radius: 10px;
  background: var(--color-surface);
  border: 1px solid var(--color-border);
  font-size: 14px;
  font-weight: 700;
  color: var(--color-accent);
  flex-shrink: 0;
}

.chapter-info h3 {
  font-size: 16px;
  font-weight: 700;
  color: var(--color-heading);
  margin-bottom: 4px;
}

.chapter-info p {
  font-size: 14px;
  color: var(--color-text-secondary);
  line-height: 1.6;
}

/* ---------- Authors ---------- */
.authors-grid {
  display: grid;
  grid-template-columns: repeat(4, 1fr);
  gap: 24px;
  margin-top: 20px;
}

.author-card {
  text-align: center;
}

.author-avatar {
  width: 96px;
  height: 96px;
  border-radius: 50%;
  background: var(--color-surface);
  border: 2px solid var(--color-border);
  display: flex;
  align-items: center;
  justify-content: center;
  margin: 0 auto 14px;
  font-size: 36px;
  color: var(--color-text-secondary);
  overflow: hidden;
}

.author-avatar img {
  width: 100%;
  height: 100%;
  object-fit: cover;
}

.author-card h3 {
  font-size: 15px;
  font-weight: 700;
  color: var(--color-heading);
  margin-bottom: 4px;
}

.author-card .author-role {
  font-size: 13px;
  color: var(--color-text-secondary);
  margin-bottom: 8px;
}

.author-links {
  display: flex;
  gap: 12px;
  justify-content: center;
}

.author-links a {
  color: var(--color-text-secondary);
  font-size: 16px;
  transition: color 0.15s ease;
}

.author-links a:hover {
  color: var(--color-accent);
}

/* ---------- Footer ---------- */
.site-footer {
  border-top: 1px solid var(--color-border);
  padding: 32px 0;
  margin-top: 16px;
}

.footer-inner {
  display: flex;
  align-items: center;
  justify-content: space-between;
}

.footer-text {
  font-size: 13px;
  color: var(--color-text-secondary);
}

.footer-links {
  display: flex;
  gap: 20px;
}

.footer-links a {
  font-size: 13px;
  color: var(--color-text-secondary);
}

.footer-links a:hover {
  color: var(--color-accent);
}

/* ---------- Responsive ---------- */
@media (max-width: 768px) {
  .hero {
    padding: 40px 0 36px;
  }

  .hero-inner {
    grid-template-columns: 1fr;
    gap: 32px;
    text-align: center;
  }

  .hero-cover {
    max-width: 220px;
    margin: 0 auto;
  }

  .hero-content h1 {
    font-size: 28px;
  }

  .hero-buttons {
    justify-content: center;
  }

  .audience-grid {
    grid-template-columns: 1fr;
  }

  .authors-grid {
    grid-template-columns: repeat(2, 1fr);
    gap: 32px;
  }

  .chapters-list li {
    grid-template-columns: 40px 1fr;
    gap: 12px;
  }

  .site-nav {
    gap: 16px;
  }

  .site-nav a {
    font-size: 13px;
  }

  .footer-inner {
    flex-direction: column;
    gap: 12px;
    text-align: center;
  }
}

@media (max-width: 480px) {
  .hero-content h1 {
    font-size: 24px;
  }

  .hero-buttons {
    flex-direction: column;
    align-items: stretch;
  }

  .btn {
    justify-content: center;
  }

  .authors-grid {
    grid-template-columns: 1fr 1fr;
    gap: 24px;
  }
}