:root {
  --bg-color: #0d1117;
  --text-color: #c9d1d9;
  --accent-color: #58a6ff;
  --card-bg: #161b22;
  --border-color: #30363d;
  --green-color: #3fb950;
  --warn-color: #f0883e;
  --muted-color: #8b949e;
}

body {
  font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Helvetica, Arial, sans-serif;
  background-color: var(--bg-color);
  color: var(--text-color);
  line-height: 1.7;
  margin: 0;
  padding: 0;
}

.container {
  max-width: 800px;
  margin: 0 auto;
  padding: 40px 20px;
}

header {
  border-bottom: 1px solid var(--border-color);
  padding-bottom: 20px;
  margin-bottom: 35px;
}

section {
  margin-top: 2rem;
}

h1,
h2,
h3,
h4 {
  color: #ffffff;
  font-weight: 700;
  margin-top: 1.4em;
  margin-bottom: 0.6em;
}

h1 {
  font-size: 2rem;
  margin-top: 0;
  letter-spacing: -0.5px;
}

h2 {
  font-size: 1.4rem;
  border-left: 4px solid var(--accent-color);
  padding-left: 12px;
}

h3 {
  font-size: 1.15rem;
}

p {
  color: var(--text-color);
}

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

a:hover {
  text-decoration: underline;
}

ul,
ol {
  padding-left: 24px;
  margin-bottom: 1.2rem;
}

li {
  margin-bottom: 0.6rem;
}

strong {
  color: #ffffff;
}

code {
  background-color: rgba(255, 255, 255, 0.06);
  color: #f9a8d4;
  padding: 2px 6px;
  border-radius: 4px;
  font-family: "Courier New", Courier, monospace;
  font-size: 0.95em;
}

pre {
  background-color: #1e1e2e;
  color: #cdd6f4;
  padding: 16px;
  border-radius: 8px;
  overflow-x: auto;
  font-family: "Courier New", Courier, monospace;
}

.nav-back {
  margin-bottom: 20px;
}

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

.chapter-number,
.category,
.badge {
  color: var(--accent-color);
  font-size: 0.9rem;
  font-weight: 600;
  display: inline-block;
}

.chapter-number,
.category {
  text-transform: uppercase;
  display: block;
  margin-bottom: 5px;
}

.badge {
  background-color: rgba(88, 166, 255, 0.1);
  padding: 5px 12px;
  border-radius: 20px;
  margin-bottom: 15px;
}

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

.target-box,
.toc-section,
.philosophy-card,
.vibe-check,
.code-box,
.diagram,
.vibe-box,
.relay-flow,
.concept-card {
  background-color: var(--card-bg);
  border: 1px solid var(--border-color);
  border-radius: 8px;
}

.target-box {
  padding: 20px;
  margin-bottom: 30px;
}

.target-box ul {
  margin: 0;
  padding-left: 20px;
}

.target-box li {
  margin-bottom: 8px;
  color: var(--text-color);
}

.philosophy-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(220px, 1fr));
  gap: 15px;
  margin-bottom: 40px;
}

.philosophy-card {
  border-left: 4px solid var(--accent-color);
  border-radius: 0 8px 8px 0;
  padding: 15px;
}

.philosophy-card.eco {
  border-left-color: var(--green-color);
}

.philosophy-card h3 {
  margin: 0 0 8px 0;
  font-size: 1.1rem;
}

.philosophy-card p {
  margin: 0;
  font-size: 0.95rem;
}

.toc-section {
  padding: 25px;
}

.toc-part {
  margin-bottom: 25px;
}

.toc-part:last-child {
  margin-bottom: 0;
}

.toc-part h4 {
  margin: 0 0 10px 0;
  color: var(--accent-color);
  font-size: 1.1rem;
}

.toc-list {
  list-style: none;
  padding: 0;
  margin: 0;
}

.toc-item {
  display: flex;
  align-items: baseline;
  padding: 8px 0;
  border-bottom: 1px solid rgba(48, 54, 61, 0.5);
}

.toc-item:last-child {
  border-bottom: none;
}

.toc-item .status {
  font-size: 0.75rem;
  padding: 2px 6px;
  border-radius: 3px;
  margin-right: 10px;
  font-weight: 600;
  white-space: nowrap;
}

.status.done {
  background-color: rgba(63, 185, 80, 0.15);
  color: var(--green-color);
}

.status.ready {
  background-color: rgba(139, 148, 158, 0.15);
  color: var(--muted-color);
}

.toc-item a {
  color: var(--text-color);
  text-decoration: none;
  font-size: 0.95rem;
  transition: color 0.2s;
}

.toc-item a:hover {
  color: var(--accent-color);
}

.vibe-check {
  padding: 15px 20px;
  margin: 25px 0;
}

.vibe-check strong {
  color: var(--warn-color);
  display: block;
  margin-bottom: 5px;
}

.vibe-check.success {
  background-color: rgba(63, 185, 80, 0.1);
  border-color: rgba(63, 185, 80, 0.3);
}

.vibe-check.success strong {
  color: var(--green-color);
}

.step-list {
  padding-left: 20px;
}

.step-list li {
  margin-bottom: 12px;
}

.step-list strong {
  color: #ffffff;
}

.code-box {
  background-color: #000000;
  padding: 15px;
  font-family: "Courier New", Courier, monospace;
  font-size: 0.9rem;
  color: var(--green-color);
  margin: 15px 0;
  overflow-x: auto;
}

.diagram {
  display: flex;
  gap: 12px;
  align-items: stretch;
  padding: 16px;
  margin: 20px 0;
}

.screen-left,
.screen-right,
.concept-card {
  flex: 1;
  padding: 16px;
}

.screen-arrow {
  display: flex;
  align-items: center;
  justify-content: center;
  font-size: 1.4rem;
  color: var(--accent-color);
}

.vibe-box {
  padding: 16px;
  margin: 18px 0;
}

.relay-flow {
  padding: 16px;
  margin: 18px 0;
}

.cloud-gray {
  color: var(--muted-color);
}

.cloud-orange {
  color: var(--warn-color);
}

.flow-step {
  display: inline-block;
  font-weight: 700;
  color: var(--accent-color);
}

.concept-card {
  border-left: 4px solid var(--border-color);
}

.edit-btn {
  background-color: var(--card-bg);
  border: 1px solid var(--border-color);
  padding: 6px 12px;
  border-radius: 4px;
  color: #c9d1d9 !important;
  transition: all 0.2s;
}

.edit-btn:hover {
  background-color: var(--border-color);
  color: #ffffff !important;
}

footer {
  margin-top: 60px;
  text-align: center;
  font-size: 0.85rem;
  color: var(--muted-color);
  border-top: 1px solid var(--border-color);
  padding-top: 20px;
  display: flex;
  justify-content: space-between;
  align-items: center;
}

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

.footer-nav {
  margin-top: 12px;
}

.footer-nav a {
  margin: 0 10px;
  color: #4a5568;
  font-weight: 500;
}

.muted-label {
  color: var(--muted-color);
  font-size: 0.85rem;
}

.accent-text {
  color: var(--accent-color);
  font-weight: 700;
}