/* ============================================================
   古法编程 · ARM 嵌入式 C 开发 — common.css
   Theme: Amber / Orange Circuit-Board
   ============================================================ */

: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:    #f59e0b;
  --accent-2:  #fbbf24;
  --green:     #4ade80;
  --blue:      #60a5fa;
  --red:       #f87171;
  --cyan:      #22d3ee;
  --radius:    8px;
  --radius-lg: 12px;
}

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

html { scroll-behavior: smooth; }

body {
  background: var(--bg);
  color: var(--text);
  font-family: system-ui, -apple-system, 'Segoe UI', sans-serif;
  font-size: 16px;
  line-height: 1.75;
  min-height: 100vh;
}

/* ── Scrollbar ── */
::-webkit-scrollbar { width: 6px; }
::-webkit-scrollbar-track { background: var(--surface); }
::-webkit-scrollbar-thumb { background: rgba(245,158,11,0.4); border-radius: 3px; }

/* ── Selection ── */
::selection { background: rgba(245,158,11,0.25); color: var(--text); }

/* ============================================================
   NAVIGATION
   ============================================================ */
.nav {
  position: sticky;
  top: 0;
  z-index: 100;
  background: rgba(13,17,23,0.94);
  backdrop-filter: blur(14px);
  -webkit-backdrop-filter: blur(14px);
  border-bottom: 1px solid var(--border);
  padding: 0 24px;
}
.nav-inner {
  max-width: 1100px;
  margin: 0 auto;
  display: flex;
  align-items: center;
  justify-content: space-between;
  height: 56px;
  gap: 16px;
}
.nav-logo {
  font-size: 15px;
  font-weight: 700;
  color: var(--accent);
  text-decoration: none;
  letter-spacing: 0.02em;
  white-space: nowrap;
}
.nav-logo:hover { color: var(--accent-2); }
.nav-title {
  font-size: 13px;
  color: var(--text-3);
  white-space: nowrap;
  overflow: hidden;
  text-overflow: ellipsis;
}
.nav-links {
  display: flex;
  gap: 4px;
  list-style: none;
  flex-shrink: 0;
}
.nav-links a {
  font-size: 13px;
  color: var(--text-3);
  text-decoration: none;
  padding: 4px 10px;
  border-radius: var(--radius);
  transition: color .18s, background .18s;
}
.nav-links a:hover { color: var(--accent); background: rgba(245,158,11,0.08); }

/* ============================================================
   HERO — index page
   ============================================================ */
.hero {
  position: relative;
  overflow: hidden;
  padding: 80px 24px 72px;
  text-align: center;
  background: radial-gradient(ellipse 80% 60% at 50% 0%, rgba(245,158,11,0.18) 0%, transparent 70%);
  border-bottom: 1px solid var(--border);
}
.hero::before {
  content: '';
  position: absolute;
  inset: 0;
  background:
    repeating-linear-gradient(0deg, transparent, transparent 39px, rgba(245,158,11,0.04) 40px),
    repeating-linear-gradient(90deg, transparent, transparent 39px, rgba(245,158,11,0.04) 40px);
  pointer-events: none;
}
.hero-badge {
  display: inline-block;
  font-size: 11px;
  font-weight: 700;
  letter-spacing: .1em;
  text-transform: uppercase;
  color: var(--accent);
  border: 1px solid var(--border-bright);
  border-radius: 20px;
  padding: 4px 14px;
  margin-bottom: 24px;
  background: rgba(245,158,11,0.08);
}
.hero h1 {
  font-size: clamp(2rem, 5vw, 3.2rem);
  font-weight: 800;
  letter-spacing: -0.02em;
  line-height: 1.2;
  margin-bottom: 16px;
  background: linear-gradient(135deg, var(--accent) 0%, var(--accent-2) 50%, #fde68a 100%);
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
  background-clip: text;
}
.hero-sub {
  font-size: clamp(1rem, 2vw, 1.15rem);
  color: var(--text-2);
  max-width: 600px;
  margin: 0 auto 32px;
  line-height: 1.7;
}
.hero-meta {
  display: flex;
  align-items: center;
  justify-content: center;
  gap: 24px;
  flex-wrap: wrap;
  font-size: 13px;
  color: var(--text-3);
}
.hero-meta span { display: flex; align-items: center; gap: 6px; }
.hero-meta strong { color: var(--accent); }

/* ============================================================
   CHAPTER HERO — chapter pages
   ============================================================ */
.chapter-hero {
  position: relative;
  overflow: hidden;
  padding: 56px 24px 48px;
  border-bottom: 1px solid var(--border);
  background: linear-gradient(180deg, rgba(245,158,11,0.10) 0%, transparent 100%);
}
.chapter-hero::after {
  content: '';
  position: absolute;
  bottom: 0; left: 0; right: 0;
  height: 1px;
  background: linear-gradient(90deg, transparent, var(--accent), transparent);
  opacity: .5;
}
.chapter-label {
  font-size: 11px;
  font-weight: 700;
  letter-spacing: .12em;
  text-transform: uppercase;
  color: var(--accent);
  margin-bottom: 12px;
}
.chapter-hero h1 {
  font-size: clamp(1.6rem, 4vw, 2.4rem);
  font-weight: 800;
  letter-spacing: -0.01em;
  line-height: 1.25;
  margin-bottom: 14px;
  color: var(--text);
}
.chapter-hero p {
  font-size: 1.05rem;
  color: var(--text-2);
  max-width: 700px;
}

/* ============================================================
   PROGRESS BAR
   ============================================================ */
.progress {
  width: 100%;
  max-width: 860px;
  margin: 20px auto 0;
  padding: 0 24px;
}
.progress-label {
  display: flex;
  justify-content: space-between;
  font-size: 12px;
  color: var(--text-3);
  margin-bottom: 6px;
}
.progress-track {
  height: 4px;
  background: var(--surface-2);
  border-radius: 2px;
  overflow: hidden;
}
.progress-bar {
  height: 100%;
  background: linear-gradient(90deg, var(--accent), var(--accent-2));
  border-radius: 2px;
  transition: width .4s ease;
}

/* ============================================================
   CONTENT AREA
   ============================================================ */
.content {
  max-width: 860px;
  margin: 0 auto;
  padding: 48px 24px 80px;
}

/* Headings */
.content h2 {
  font-size: 1.5rem;
  font-weight: 700;
  color: var(--text);
  margin: 48px 0 16px;
  padding-bottom: 10px;
  border-bottom: 1px solid var(--border);
  letter-spacing: -0.01em;
}
.content h2:first-child { margin-top: 0; }
.content h3 {
  font-size: 1.15rem;
  font-weight: 600;
  color: var(--accent-2);
  margin: 32px 0 12px;
}
.content h4 {
  font-size: 1rem;
  font-weight: 600;
  color: var(--text-2);
  margin: 24px 0 8px;
}

/* Paragraphs & lists */
.content p { color: var(--text-2); margin-bottom: 16px; }
.content ul, .content ol {
  color: var(--text-2);
  padding-left: 24px;
  margin-bottom: 16px;
}
.content li { margin-bottom: 6px; }
.content strong { color: var(--text); font-weight: 600; }
.content em { color: var(--accent-2); font-style: normal; }
.content a { color: var(--accent); text-decoration: underline; text-underline-offset: 3px; }
.content a:hover { color: var(--accent-2); }

/* Inline code */
.content code {
  font-family: 'JetBrains Mono','Fira Code','SF Mono',Consolas,monospace;
  font-size: .85em;
  background: rgba(245,158,11,0.12);
  color: var(--accent-2);
  padding: 2px 6px;
  border-radius: 4px;
  border: 1px solid rgba(245,158,11,0.2);
}

/* ============================================================
   CODE BLOCKS
   ============================================================ */
pre[data-lang] {
  position: relative;
  background: var(--surface);
  border: 1px solid var(--border);
  border-left: 3px solid var(--accent);
  border-radius: var(--radius);
  padding: 36px 20px 20px;
  overflow-x: auto;
  margin: 20px 0;
  font-family: 'JetBrains Mono','Fira Code','SF Mono',Consolas,monospace;
  font-size: 13.5px;
  line-height: 1.7;
  color: var(--text-2);
}
pre[data-lang]::before {
  content: attr(data-lang);
  position: absolute;
  top: 0; right: 0;
  font-size: 10px;
  font-weight: 700;
  letter-spacing: .08em;
  text-transform: uppercase;
  color: var(--accent);
  background: rgba(245,158,11,0.12);
  border-bottom-left-radius: var(--radius);
  padding: 3px 10px;
  border-left: 1px solid var(--border);
  border-bottom: 1px solid var(--border);
}
pre[data-lang] code {
  background: none;
  border: none;
  padding: 0;
  font-size: inherit;
  color: inherit;
  border-radius: 0;
}

/* Syntax highlight spans */
.kw { color: var(--accent);   font-weight: 600; }  /* keywords         */
.fn { color: var(--accent-2); }                     /* functions        */
.st { color: var(--green);    }                     /* strings          */
.cm { color: var(--text-3);   font-style: italic; } /* comments         */
.ty { color: var(--cyan);     }                     /* types            */
.nu { color: #c084fc;         }                     /* numbers/literals */
.at { color: var(--red);      }                     /* attributes/macros*/
.pr { color: var(--blue);     }                     /* preprocessor     */

/* ============================================================
   ASCII FLOW DIAGRAM
   ============================================================ */
.ascii-flow {
  font-family: 'JetBrains Mono','Fira Code','SF Mono',Consolas,monospace;
  font-size: 12.5px;
  line-height: 1.6;
  color: var(--text-2);
  background: var(--surface);
  border: 1px solid var(--border-bright);
  border-radius: var(--radius);
  padding: 20px 24px;
  overflow-x: auto;
  margin: 20px 0;
  white-space: pre;
}
.ascii-flow .ac  { color: var(--accent); }
.ascii-flow .ac2 { color: var(--accent-2); }
.ascii-flow .gn  { color: var(--green); }
.ascii-flow .cy  { color: var(--cyan); }
.ascii-flow .rd  { color: var(--red); }
.ascii-flow .bl  { color: var(--blue); }

/* ============================================================
   REGISTER MAP
   ============================================================ */
.register-map {
  background: var(--surface);
  border: 1px solid var(--border-bright);
  border-radius: var(--radius);
  padding: 20px 24px;
  margin: 20px 0;
  overflow-x: auto;
}
.register-map h4 {
  font-family: 'JetBrains Mono','Fira Code','SF Mono',Consolas,monospace;
  font-size: 13px;
  color: var(--accent);
  margin-bottom: 12px;
}
.register-map table {
  border-collapse: collapse;
  width: 100%;
  font-family: 'JetBrains Mono','Fira Code','SF Mono',Consolas,monospace;
  font-size: 12px;
}
.register-map th {
  background: rgba(245,158,11,0.15);
  color: var(--accent);
  padding: 6px 10px;
  border: 1px solid var(--border);
  text-align: center;
  white-space: nowrap;
}
.register-map td {
  padding: 6px 10px;
  border: 1px solid var(--border);
  color: var(--text-2);
  text-align: center;
  white-space: nowrap;
}
.register-map td.rw { color: var(--green); }
.register-map td.ro { color: var(--blue); }
.register-map td.res { color: var(--text-3); font-style: italic; }

/* ============================================================
   DEFINITION LIST
   ============================================================ */
.def-list {
  display: grid;
  grid-template-columns: 1fr;
  gap: 12px;
  margin: 20px 0;
}
.def-item {
  background: var(--card);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 14px 18px;
  transition: border-color .2s, background .2s;
}
.def-item:hover {
  border-color: var(--border-bright);
  background: var(--card-hover);
}
.def-term {
  font-size: .9rem;
  font-weight: 700;
  color: var(--accent);
  font-family: 'JetBrains Mono','Fira Code','SF Mono',Consolas,monospace;
  margin-bottom: 6px;
}
.def-desc {
  font-size: .9rem;
  color: var(--text-2);
  line-height: 1.65;
}

/* ============================================================
   CALLOUT BOXES
   ============================================================ */
.callout {
  border-radius: var(--radius);
  padding: 16px 20px;
  margin: 20px 0;
  border-left: 4px solid;
  display: flex;
  flex-direction: column;
  gap: 6px;
}
.callout-title {
  font-size: .85rem;
  font-weight: 700;
  letter-spacing: .05em;
  text-transform: uppercase;
}
.callout p { margin: 0; font-size: .92rem; line-height: 1.65; }
.callout code { font-size: .82em; }

.callout.info {
  background: rgba(96,165,250,0.08);
  border-color: var(--blue);
}
.callout.info .callout-title { color: var(--blue); }
.callout.info p { color: #93c5fd; }

.callout.tip {
  background: rgba(245,158,11,0.08);
  border-color: var(--accent);
}
.callout.tip .callout-title { color: var(--accent); }
.callout.tip p { color: var(--text-2); }

.callout.warning {
  background: rgba(251,191,36,0.08);
  border-color: var(--accent-2);
}
.callout.warning .callout-title { color: var(--accent-2); }
.callout.warning p { color: #fde68a; }

.callout.danger {
  background: rgba(248,113,113,0.08);
  border-color: var(--red);
}
.callout.danger .callout-title { color: var(--red); }
.callout.danger p { color: #fca5a5; }

/* ============================================================
   TWO-COLUMN LAYOUT
   ============================================================ */
.two-col {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 16px;
  margin: 20px 0;
}
.two-col-item {
  background: var(--card);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 16px 18px;
}
.two-col-item h4 {
  font-size: .9rem;
  font-weight: 700;
  color: var(--accent);
  margin-bottom: 10px;
}
.two-col-item ul { padding-left: 18px; margin: 0; }
.two-col-item li { font-size: .88rem; color: var(--text-2); margin-bottom: 5px; }
@media (max-width: 600px) { .two-col { grid-template-columns: 1fr; } }

/* ============================================================
   COMPARE TABLE
   ============================================================ */
.compare-table {
  width: 100%;
  border-collapse: collapse;
  margin: 20px 0;
  font-size: .9rem;
}
.compare-table th {
  background: rgba(245,158,11,0.15);
  color: var(--accent);
  padding: 10px 14px;
  text-align: left;
  border: 1px solid var(--border);
  font-weight: 700;
}
.compare-table td {
  padding: 10px 14px;
  border: 1px solid var(--border);
  color: var(--text-2);
  vertical-align: top;
}
.compare-table tr:nth-child(even) td { background: rgba(245,158,11,0.03); }
.compare-table tr:hover td { background: rgba(245,158,11,0.06); }

/* ============================================================
   CARD GRID — index page
   ============================================================ */
.card-grid {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(300px, 1fr));
  gap: 20px;
  padding: 40px 24px;
  max-width: 1100px;
  margin: 0 auto;
}
.card {
  background: var(--card);
  border: 1px solid var(--border);
  border-radius: var(--radius-lg);
  padding: 24px;
  text-decoration: none;
  display: flex;
  flex-direction: column;
  gap: 10px;
  transition: border-color .2s, background .2s, transform .2s, box-shadow .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 .2s;
}
.card:hover {
  border-color: var(--border-bright);
  background: var(--card-hover);
  transform: translateY(-2px);
  box-shadow: 0 8px 32px rgba(245,158,11,0.12);
}
.card:hover::before { opacity: 1; }

.card-num {
  font-size: 11px;
  font-weight: 700;
  letter-spacing: .1em;
  text-transform: uppercase;
  color: var(--accent);
  font-family: 'JetBrains Mono','Fira Code','SF Mono',Consolas,monospace;
}
.card-title {
  font-size: 1.05rem;
  font-weight: 700;
  color: var(--text);
  line-height: 1.3;
}
.card-desc {
  font-size: .875rem;
  color: var(--text-3);
  line-height: 1.6;
  flex: 1;
}
.card-tags {
  display: flex;
  flex-wrap: wrap;
  gap: 6px;
  margin-top: 4px;
}
.tag {
  font-size: 11px;
  font-weight: 600;
  padding: 3px 8px;
  border-radius: 4px;
  background: rgba(245,158,11,0.12);
  color: var(--accent-2);
  border: 1px solid rgba(245,158,11,0.2);
  font-family: 'JetBrains Mono','Fira Code','SF Mono',Consolas,monospace;
}
.tag.green { background: rgba(74,222,128,0.10); color: var(--green); border-color: rgba(74,222,128,0.2); }
.tag.blue  { background: rgba(96,165,250,0.10); color: var(--blue);  border-color: rgba(96,165,250,0.2); }
.tag.cyan  { background: rgba(34,211,238,0.10); color: var(--cyan);  border-color: rgba(34,211,238,0.2); }
.tag.red   { background: rgba(248,113,113,0.10); color: var(--red);  border-color: rgba(248,113,113,0.2); }

/* ============================================================
   CHAPTER NAVIGATION
   ============================================================ */
.chapter-nav {
  display: flex;
  justify-content: space-between;
  gap: 16px;
  margin-top: 64px;
  padding-top: 32px;
  border-top: 1px solid var(--border);
}
.chapter-nav a {
  display: flex;
  flex-direction: column;
  gap: 4px;
  padding: 16px 20px;
  background: var(--card);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  text-decoration: none;
  min-width: 180px;
  max-width: 48%;
  transition: border-color .2s, background .2s;
}
.chapter-nav a:hover {
  border-color: var(--border-bright);
  background: var(--card-hover);
}
.chapter-nav .nav-dir {
  font-size: 11px;
  font-weight: 700;
  letter-spacing: .08em;
  text-transform: uppercase;
  color: var(--accent);
}
.chapter-nav .nav-name {
  font-size: .9rem;
  font-weight: 600;
  color: var(--text);
}
.chapter-nav .prev { align-items: flex-start; }
.chapter-nav .next { align-items: flex-end; margin-left: auto; }
.chapter-nav .nav-dir::before { content: '← '; }
.chapter-nav .next .nav-dir::before { content: ''; }
.chapter-nav .next .nav-dir::after { content: ' →'; }

/* ============================================================
   SITE FOOTER
   ============================================================ */
.site-footer {
  text-align: center;
  padding: 24px;
  border-top: 1px solid var(--border);
  font-size: .825rem;
  color: var(--text-3);
  background: var(--surface);
}
.site-footer a {
  color: var(--accent);
  text-decoration: none;
  font-weight: 600;
}
.site-footer a:hover { color: var(--accent-2); }

/* ============================================================
   SECTION DIVIDER
   ============================================================ */
.section-label {
  font-size: 11px;
  font-weight: 700;
  letter-spacing: .12em;
  text-transform: uppercase;
  color: var(--accent);
  padding: 32px 24px 8px;
  max-width: 1100px;
  margin: 0 auto;
}

/* ============================================================
   UTILITY
   ============================================================ */
.text-accent  { color: var(--accent); }
.text-accent2 { color: var(--accent-2); }
.text-green   { color: var(--green); }
.text-blue    { color: var(--blue); }
.text-cyan    { color: var(--cyan); }
.text-red     { color: var(--red); }
.text-muted   { color: var(--text-3); }
.mono         { font-family: 'JetBrains Mono','Fira Code','SF Mono',Consolas,monospace; }
.mt-0         { margin-top: 0; }

/* ============================================================
   RESPONSIVE
   ============================================================ */
@media (max-width: 768px) {
  .hero          { padding: 56px 16px 48px; }
  .chapter-hero  { padding: 40px 16px 32px; }
  .content       { padding: 32px 16px 60px; }
  .card-grid     { padding: 24px 16px; }
  .progress      { padding: 0 16px; }
  .chapter-nav   { flex-direction: column; }
  .chapter-nav a { max-width: 100%; min-width: auto; }
  .nav-title     { display: none; }
  pre[data-lang] { font-size: 12px; padding: 32px 14px 14px; }
}