/* ============================================
   系统设计教程 — 蓝图工程感主题
   common.css
   ============================================ */

:root {
  --bg: #0d1117;
  --surface: #161b22;
  --surface-2: #21262d;
  --card: #1c2128;
  --card-hover: #262c36;
  --border: rgba(180,185,210,0.12);
  --border-bright: rgba(180,185,210,0.26);
  --text: #e6edf3;
  --text-2: #adbac7;
  --text-3: #768390;
  --accent: #00d4ff;
  --accent-2: #38bdf8;
  --accent-glow: rgba(0,212,255,0.15);
  --green: #4ade80;
  --orange: #fb923c;
  --red: #f87171;
  --purple: #c084fc;
  --yellow: #fbbf24;
  --grid-color: rgba(180,185,210,0.04);
  --radius: 10px;
  --radius-lg: 14px;
}

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

html { scroll-behavior: smooth; }

body {
  font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', 'PingFang SC', 'Hiragino Sans GB', 'Microsoft YaHei', sans-serif;
  background-color: var(--bg);
  color: var(--text);
  line-height: 1.75;
  min-height: 100vh;
  background-image:
    linear-gradient(var(--grid-color) 1px, transparent 1px),
    linear-gradient(90deg, var(--grid-color) 1px, transparent 1px);
  background-size: 40px 40px;
}

/* ── NAV ───────────────────────────────────── */
.nav {
  position: sticky;
  top: 0;
  z-index: 100;
  display: flex;
  align-items: center;
  gap: 16px;
  padding: 0 28px;
  height: 56px;
  background: rgba(13,17,23,0.94);
  border-bottom: 1px solid var(--border);
  backdrop-filter: blur(16px);
}

.nav-back {
  color: var(--accent);
  text-decoration: none;
  font-size: 0.85rem;
  font-weight: 600;
  letter-spacing: 0.04em;
  opacity: 0.8;
  transition: opacity 0.2s;
  display: flex;
  align-items: center;
  gap: 6px;
}
.nav-back::before { content: '←'; }
.nav-back:hover { opacity: 1; }

.nav-sep {
  color: var(--text-3);
  font-size: 0.85rem;
}

.nav-title {
  font-size: 0.92rem;
  font-weight: 600;
  color: var(--text);
  letter-spacing: 0.02em;
}

/* ── HERO (index) ───────────────────────────── */
.hero {
  position: relative;
  overflow: hidden;
  padding: 100px 28px 80px;
  text-align: center;
  background: radial-gradient(ellipse 80% 60% at 50% 0%, rgba(0,212,255,0.1) 0%, transparent 70%);
  border-bottom: 1px solid var(--border);
}

.hero::before {
  content: '';
  position: absolute;
  inset: 0;
  background-image:
    linear-gradient(rgba(0,212,255,0.06) 1px, transparent 1px),
    linear-gradient(90deg, rgba(0,212,255,0.06) 1px, transparent 1px);
  background-size: 60px 60px;
  mask-image: radial-gradient(ellipse 70% 80% at 50% 0%, black 0%, transparent 100%);
  pointer-events: none;
}

.hero-label {
  display: inline-flex;
  align-items: center;
  gap: 8px;
  font-size: 0.78rem;
  font-weight: 600;
  letter-spacing: 0.12em;
  text-transform: uppercase;
  color: var(--accent);
  background: var(--accent-glow);
  border: 1px solid var(--border-bright);
  padding: 5px 14px;
  border-radius: 20px;
  margin-bottom: 24px;
}

.hero h1 {
  font-size: clamp(2.2rem, 5vw, 3.6rem);
  font-weight: 800;
  letter-spacing: -0.02em;
  line-height: 1.15;
  margin-bottom: 16px;
  background: linear-gradient(135deg, #e8f0fe 0%, var(--accent) 60%, var(--accent-2) 100%);
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
  background-clip: text;
}

.hero p {
  font-size: 1.1rem;
  color: var(--text-2);
  max-width: 620px;
  margin: 0 auto 40px;
  line-height: 1.65;
}

.hero-stats {
  display: flex;
  justify-content: center;
  gap: 40px;
  flex-wrap: wrap;
}

.stat {
  text-align: center;
}

.stat-num {
  display: block;
  font-size: 1.8rem;
  font-weight: 800;
  color: var(--accent);
  line-height: 1.1;
}

.stat-label {
  font-size: 0.8rem;
  color: var(--text-3);
  letter-spacing: 0.06em;
  text-transform: uppercase;
  margin-top: 4px;
}

/* ── CONTAINER ──────────────────────────────── */
.container {
  max-width: 1140px;
  margin: 0 auto;
  padding: 60px 28px;
}

.section-title {
  font-size: 0.78rem;
  font-weight: 700;
  letter-spacing: 0.12em;
  text-transform: uppercase;
  color: var(--accent);
  margin-bottom: 32px;
  display: flex;
  align-items: center;
  gap: 12px;
}

.section-title::after {
  content: '';
  flex: 1;
  height: 1px;
  background: linear-gradient(90deg, var(--border-bright), transparent);
}

/* ── CARDS GRID ─────────────────────────────── */
.card-grid {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(300px, 1fr));
  gap: 20px;
}

.card {
  background: var(--card);
  border: 1px solid var(--border);
  border-radius: var(--radius-lg);
  padding: 24px;
  text-decoration: none;
  color: var(--text);
  display: flex;
  flex-direction: column;
  gap: 12px;
  transition: background 0.2s, border-color 0.2s, transform 0.2s, box-shadow 0.2s;
  position: relative;
  overflow: hidden;
}

.card::before {
  content: '';
  position: absolute;
  top: 0; left: 0; right: 0;
  height: 2px;
  background: linear-gradient(90deg, var(--accent), var(--accent-2));
  opacity: 0;
  transition: opacity 0.2s;
}

.card:hover {
  background: var(--card-hover);
  border-color: var(--border-bright);
  transform: translateY(-3px);
  box-shadow: 0 12px 40px rgba(0,212,255,0.1);
}

.card:hover::before { opacity: 1; }

.card-num {
  font-size: 0.72rem;
  font-weight: 700;
  letter-spacing: 0.1em;
  color: var(--accent);
  opacity: 0.7;
  text-transform: uppercase;
}

.card h3 {
  font-size: 1.05rem;
  font-weight: 700;
  color: var(--text);
  line-height: 1.35;
}

.card p {
  font-size: 0.87rem;
  color: var(--text-2);
  line-height: 1.6;
  flex: 1;
}

.card-tags {
  display: flex;
  flex-wrap: wrap;
  gap: 6px;
  margin-top: 4px;
}

.tag {
  font-size: 0.72rem;
  font-weight: 600;
  padding: 3px 9px;
  border-radius: 4px;
  background: rgba(0,212,255,0.08);
  color: var(--accent-2);
  border: 1px solid rgba(0,212,255,0.15);
  letter-spacing: 0.03em;
}

.card-arrow {
  color: var(--accent);
  font-size: 1rem;
  transition: transform 0.2s;
  align-self: flex-end;
}

.card:hover .card-arrow { transform: translateX(4px); }

/* ── CHAPTER HERO ───────────────────────────── */
.chapter-hero {
  position: relative;
  overflow: hidden;
  padding: 72px 28px 56px;
  background: radial-gradient(ellipse 70% 80% at 50% 0%, rgba(0,212,255,0.08) 0%, transparent 65%);
  border-bottom: 1px solid var(--border);
  text-align: center;
}

.chapter-hero::before {
  content: '';
  position: absolute;
  inset: 0;
  background-image:
    linear-gradient(rgba(0,212,255,0.05) 1px, transparent 1px),
    linear-gradient(90deg, rgba(0,212,255,0.05) 1px, transparent 1px);
  background-size: 48px 48px;
  mask-image: radial-gradient(ellipse 80% 100% at 50% 0%, black, transparent);
  pointer-events: none;
}

.ch-num {
  font-size: 0.75rem;
  font-weight: 700;
  letter-spacing: 0.14em;
  text-transform: uppercase;
  color: var(--accent);
  opacity: 0.7;
  margin-bottom: 16px;
}

.chapter-hero h1 {
  font-size: clamp(1.8rem, 4vw, 2.8rem);
  font-weight: 800;
  letter-spacing: -0.02em;
  line-height: 1.2;
  margin-bottom: 16px;
  background: linear-gradient(135deg, #e8f0fe 30%, var(--accent));
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
  background-clip: text;
}

.chapter-hero p {
  font-size: 1.05rem;
  color: var(--text-2);
  max-width: 580px;
  margin: 0 auto;
  line-height: 1.65;
}

/* ── CONTENT ────────────────────────────────── */
.content {
  max-width: 860px;
  margin: 0 auto;
  padding: 48px 28px 80px;
}

.content h2 {
  font-size: 1.5rem;
  font-weight: 700;
  color: var(--text);
  margin: 52px 0 18px;
  padding-bottom: 12px;
  border-bottom: 1px solid var(--border);
  display: flex;
  align-items: center;
  gap: 10px;
}

.content h2::before {
  content: '';
  display: inline-block;
  width: 4px;
  height: 1.2em;
  background: linear-gradient(180deg, var(--accent), var(--accent-2));
  border-radius: 2px;
  flex-shrink: 0;
}

.content h3 {
  font-size: 1.15rem;
  font-weight: 700;
  color: var(--accent-2);
  margin: 32px 0 12px;
}

.content h4 {
  font-size: 1rem;
  font-weight: 600;
  color: var(--text);
  margin: 24px 0 8px;
}

.content p {
  color: var(--text-2);
  margin-bottom: 16px;
  line-height: 1.8;
}

.content ul, .content ol {
  color: var(--text-2);
  padding-left: 24px;
  margin-bottom: 16px;
}

.content li { margin-bottom: 8px; line-height: 1.75; }

.content strong { color: var(--text); font-weight: 600; }

.content a {
  color: var(--accent);
  text-decoration: none;
  border-bottom: 1px solid rgba(0,212,255,0.3);
  transition: border-color 0.2s;
}
.content a:hover { border-color: var(--accent); }

/* ── PROGRESS BAR ───────────────────────────── */
.progress {
  height: 4px;
  background: var(--surface-2);
  border-radius: 2px;
  margin-bottom: 48px;
  overflow: hidden;
}

.progress-bar {
  height: 100%;
  background: linear-gradient(90deg, var(--accent), var(--accent-2));
  border-radius: 2px;
  box-shadow: 0 0 12px rgba(0,212,255,0.4);
  transition: width 0.6s ease;
}

/* ── ARCH DIAGRAM ───────────────────────────── */
.arch-diagram {
  font-family: 'Fira Code', 'Cascadia Code', 'JetBrains Mono', 'Courier New', monospace;
  background: #090d12;
  padding: 24px 28px;
  border-radius: var(--radius);
  border: 1px solid var(--border-bright);
  white-space: pre;
  overflow-x: auto;
  line-height: 1.55;
  color: var(--accent);
  font-size: 0.85rem;
  margin: 24px 0;
  box-shadow: inset 0 0 40px rgba(0,212,255,0.03), 0 4px 24px rgba(0,0,0,0.4);
}

/* ── CODE ───────────────────────────────────── */
pre {
  background: #090d12;
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 22px 24px;
  overflow-x: auto;
  margin: 20px 0;
  font-size: 0.87rem;
  line-height: 1.65;
}

code {
  font-family: 'Fira Code', 'Cascadia Code', 'JetBrains Mono', monospace;
  font-size: 0.875em;
}

p code, li code {
  background: rgba(0,212,255,0.08);
  border: 1px solid var(--border);
  color: var(--accent-2);
  padding: 2px 7px;
  border-radius: 4px;
}

.kw { color: #c084fc; }
.ty { color: #38bdf8; }
.st { color: #4ade80; }
.cm { color: #5c8a7a; font-style: italic; }
.fn { color: #00d4ff; }
.nu { color: #fb923c; }
.at { color: #fbbf24; }
.pr { color: #f87171; }

/* ── CALLOUT ────────────────────────────────── */
.callout {
  border-radius: var(--radius);
  padding: 18px 22px;
  margin: 24px 0;
  border-left: 4px solid;
  position: relative;
}

.callout-title {
  font-size: 0.82rem;
  font-weight: 700;
  letter-spacing: 0.08em;
  text-transform: uppercase;
  margin-bottom: 8px;
  display: flex;
  align-items: center;
  gap: 7px;
}

.callout p { margin: 0; font-size: 0.93rem; }
.callout p + p { margin-top: 8px; }
.callout ul { margin: 0; padding-left: 20px; }
.callout li { margin-bottom: 4px; font-size: 0.93rem; }

.callout.info {
  background: rgba(0,212,255,0.07);
  border-color: var(--accent);
}
.callout.info .callout-title { color: var(--accent); }

.callout.tip {
  background: rgba(74,222,128,0.07);
  border-color: var(--green);
}
.callout.tip .callout-title { color: var(--green); }

.callout.warning {
  background: rgba(251,146,60,0.07);
  border-color: var(--orange);
}
.callout.warning .callout-title { color: var(--orange); }

.callout.danger {
  background: rgba(248,113,113,0.07);
  border-color: var(--red);
}
.callout.danger .callout-title { color: var(--red); }

.callout.interview {
  background: rgba(192,132,252,0.07);
  border-color: var(--purple);
}
.callout.interview .callout-title { color: var(--purple); }

/* ── DEF LIST ───────────────────────────────── */
.def-list {
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: var(--radius-lg);
  overflow: hidden;
  margin: 20px 0;
}

.def-item {
  display: grid;
  grid-template-columns: 180px 1fr;
  border-bottom: 1px solid var(--border);
}

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

.def-term {
  padding: 14px 18px;
  font-weight: 600;
  font-size: 0.88rem;
  color: var(--accent-2);
  background: rgba(0,212,255,0.04);
  border-right: 1px solid var(--border);
  display: flex;
  align-items: flex-start;
}

.def-desc {
  padding: 14px 18px;
  font-size: 0.88rem;
  color: var(--text-2);
  line-height: 1.7;
}

/* ── TWO COL / TABLE ────────────────────────── */
.two-col {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 16px;
  margin: 20px 0;
}

@media (max-width: 640px) { .two-col { grid-template-columns: 1fr; } }

.col-box {
  background: var(--card);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 18px 20px;
}

.col-box h4 {
  font-size: 0.88rem;
  font-weight: 700;
  color: var(--accent);
  margin-bottom: 12px !important;
  padding-bottom: 8px;
  border-bottom: 1px solid var(--border);
}

.col-box ul { margin: 0; }
.col-box li { font-size: 0.88rem; margin-bottom: 6px; }

table {
  width: 100%;
  border-collapse: collapse;
  margin: 20px 0;
  font-size: 0.88rem;
}

th {
  background: rgba(0,212,255,0.08);
  color: var(--accent-2);
  font-weight: 600;
  padding: 12px 16px;
  text-align: left;
  border-bottom: 2px solid var(--border-bright);
  letter-spacing: 0.04em;
  font-size: 0.82rem;
}

td {
  padding: 11px 16px;
  color: var(--text-2);
  border-bottom: 1px solid var(--border);
  vertical-align: top;
  line-height: 1.65;
}

tr:hover td { background: rgba(0,212,255,0.03); }

/* ── HIGHLIGHT BOXES ────────────────────────── */
.highlight-box {
  background: var(--card);
  border: 1px solid var(--border);
  border-radius: var(--radius-lg);
  padding: 24px 28px;
  margin: 24px 0;
}

.highlight-box.accent {
  border-color: var(--border-bright);
  background: linear-gradient(135deg, rgba(0,212,255,0.06) 0%, transparent 60%);
}

/* ── CHAPTER NAV ────────────────────────────── */
.chapter-nav {
  display: flex;
  justify-content: space-between;
  gap: 16px;
  margin-top: 72px;
  padding-top: 28px;
  border-top: 1px solid var(--border);
  flex-wrap: wrap;
}

.chapter-nav a {
  display: flex;
  flex-direction: column;
  gap: 4px;
  padding: 16px 22px;
  background: var(--card);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  text-decoration: none;
  color: var(--text);
  flex: 1;
  min-width: 200px;
  transition: background 0.2s, border-color 0.2s, transform 0.15s;
}

.chapter-nav a:hover {
  background: var(--card-hover);
  border-color: var(--border-bright);
  transform: translateY(-2px);
}

.chapter-nav .nav-hint {
  font-size: 0.75rem;
  color: var(--text-3);
  text-transform: uppercase;
  letter-spacing: 0.08em;
  font-weight: 600;
}

.chapter-nav .nav-label {
  font-size: 0.92rem;
  font-weight: 600;
  color: var(--accent-2);
}

.chapter-nav .next { text-align: right; }

/* ── FOOTER ─────────────────────────────────── */
.site-footer {
  text-align: center;
  padding: 28px;
  color: var(--text-3);
  font-size: 0.82rem;
  border-top: 1px solid var(--border);
  background: rgba(13,17,23,0.8);
  letter-spacing: 0.04em;
}

.site-footer a {
  color: var(--accent);
  text-decoration: none;
  opacity: 0.8;
  transition: opacity 0.2s;
}
.site-footer a:hover { opacity: 1; }

/* ── BADGE / PILL ───────────────────────────── */
.badge {
  display: inline-block;
  font-size: 0.72rem;
  font-weight: 700;
  padding: 3px 9px;
  border-radius: 4px;
  text-transform: uppercase;
  letter-spacing: 0.06em;
}
.badge-blue { background: rgba(0,212,255,0.12); color: var(--accent); }
.badge-green { background: rgba(74,222,128,0.12); color: var(--green); }
.badge-orange { background: rgba(251,146,60,0.12); color: var(--orange); }
.badge-red { background: rgba(248,113,113,0.12); color: var(--red); }
.badge-purple { background: rgba(192,132,252,0.12); color: var(--purple); }

/* ── STEP LIST ──────────────────────────────── */
.step-list {
  list-style: none;
  padding: 0;
  counter-reset: step;
}

.step-list li {
  counter-increment: step;
  display: flex;
  gap: 14px;
  margin-bottom: 16px;
  align-items: flex-start;
}

.step-list li::before {
  content: counter(step);
  flex-shrink: 0;
  width: 28px;
  height: 28px;
  background: rgba(0,212,255,0.12);
  border: 1px solid var(--border-bright);
  color: var(--accent);
  font-size: 0.8rem;
  font-weight: 700;
  display: flex;
  align-items: center;
  justify-content: center;
  border-radius: 50%;
  margin-top: 2px;
}

/* ── ANIMATIONS ─────────────────────────────── */
@keyframes fadeInUp {
  from { opacity: 0; transform: translateY(20px); }
  to   { opacity: 1; transform: translateY(0); }
}

.fade-in { animation: fadeInUp 0.5s ease both; }
.delay-1 { animation-delay: 0.1s; }
.delay-2 { animation-delay: 0.2s; }
.delay-3 { animation-delay: 0.3s; }

/* ── RESPONSIVE ─────────────────────────────── */
@media (max-width: 768px) {
  .content { padding: 32px 20px 60px; }
  .container { padding: 40px 20px; }
  .hero { padding: 60px 20px 50px; }
  .chapter-hero { padding: 48px 20px 40px; }
  .def-item { grid-template-columns: 1fr; }
  .def-term { border-right: none; border-bottom: 1px solid var(--border); }
  .arch-diagram { font-size: 0.75rem; padding: 16px; }
  .chapter-nav a { min-width: 160px; }
}