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

:root {
  --go-cyan: #00ADD8;
  --go-cyan-dark: #0097B8;
  --go-cyan-light: #E6F7FB;
  --go-dark: #292929;
  --go-dark-2: #3C3C3C;
  --text-primary: #1a1a2e;
  --text-secondary: #555;
  --text-light: #888;
  --bg-white: #ffffff;
  --bg-light: #f8f9fa;
  --bg-alt: #f0f2f5;
  --border-color: #e0e0e0;
  --code-bg: #1e1e2e;
  --code-text: #d4d4d4;
  --shadow-sm: 0 1px 3px rgba(0,0,0,0.08);
  --shadow-md: 0 4px 12px rgba(0,0,0,0.1);
  --shadow-lg: 0 8px 30px rgba(0,0,0,0.12);
  --radius: 12px;
  --radius-sm: 8px;
  --max-width: 1140px;
  --font-sans: -apple-system, BlinkMacSystemFont, "Segoe UI", "PingFang SC", "Hiragino Sans GB", "Microsoft YaHei", "Helvetica Neue", Arial, sans-serif;
  --font-mono: "JetBrains Mono", "Fira Code", "SF Mono", "Cascadia Code", Menlo, Monaco, Consolas, monospace;
}

html { scroll-behavior: smooth; scroll-padding-top: 70px; }

body {
  font-family: var(--font-sans);
  color: var(--text-primary);
  background: var(--bg-white);
  line-height: 1.7;
  -webkit-font-smoothing: antialiased;
  -moz-osx-font-smoothing: grayscale;
}

a { color: var(--go-cyan-dark); text-decoration: none; transition: color 0.2s; }
a:hover { color: var(--go-cyan); }

code, pre { font-family: var(--font-mono); font-size: 0.9em; }

code {
  background: var(--go-cyan-light);
  color: var(--go-cyan-dark);
  padding: 2px 6px;
  border-radius: 4px;
  font-size: 0.88em;
}

pre code { background: none; color: var(--code-text); padding: 0; }

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

/* ===== Navbar ===== */
#navbar {
  position: fixed; top: 0; left: 0; right: 0;
  height: 64px;
  background: rgba(255,255,255,0.95);
  backdrop-filter: blur(12px);
  -webkit-backdrop-filter: blur(12px);
  border-bottom: 1px solid var(--border-color);
  z-index: 1000;
  transition: box-shadow 0.3s;
}
#navbar.scrolled { box-shadow: var(--shadow-sm); }

.nav-container {
  max-width: var(--max-width);
  margin: 0 auto;
  height: 100%;
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding: 0 24px;
}

.nav-logo { display: flex; align-items: center; gap: 8px; }
.logo-icon {
  font-family: var(--font-mono);
  font-weight: 700;
  font-size: 22px;
  color: white;
  background: var(--go-cyan);
  padding: 4px 12px;
  border-radius: 8px;
  letter-spacing: -0.5px;
}

.nav-links { display: flex; align-items: center; gap: 28px; }
.nav-links a {
  color: var(--text-secondary);
  font-size: 15px;
  font-weight: 500;
  transition: color 0.2s;
}
.nav-links a:hover { color: var(--go-cyan-dark); }
.nav-links a.nav-github {
  background: var(--go-dark);
  color: white;
  padding: 7px 16px;
  border-radius: 8px;
  font-size: 14px;
  transition: background 0.2s;
}
.nav-links a.nav-github:hover { background: var(--go-cyan); }

/* ===== Language switch ===== */
.lang-switch {
  display: inline-flex;
  border: 1px solid var(--border-color);
  border-radius: 8px;
  overflow: hidden;
  flex-shrink: 0;
  margin-left: 16px;
}
.lang-switch button {
  background: var(--bg-white);
  border: none;
  padding: 6px 12px;
  font-size: 13px;
  font-weight: 600;
  cursor: pointer;
  color: var(--text-secondary);
  transition: all 0.2s;
  font-family: var(--font-sans);
  line-height: 1.3;
}
.lang-switch button + button { border-left: 1px solid var(--border-color); }
.lang-switch button.active { background: var(--go-cyan); color: #fff; }
.lang-switch button:hover:not(.active) { color: var(--go-cyan-dark); }

.nav-toggle {
  display: none;
  flex-direction: column;
  gap: 5px;
  margin-left: 14px;
  background: none;
  border: none;
  cursor: pointer;
  padding: 4px;
}
.nav-toggle span {
  width: 24px; height: 2px;
  background: var(--text-primary);
  border-radius: 2px;
  transition: 0.3s;
}

/* ===== Hero ===== */
#hero {
  position: relative;
  min-height: 100vh;
  display: flex;
  align-items: center;
  justify-content: center;
  overflow: hidden;
  padding: 80px 24px 40px;
}

.hero-bg {
  position: absolute;
  top: 0; left: 0; right: 0; bottom: 0;
  background: linear-gradient(135deg, #f0fdff 0%, #e6f7fb 30%, #f8f9fa 70%, #ffffff 100%);
  z-index: -2;
}
.hero-bg::before {
  content: '';
  position: absolute;
  top: -200px; right: -200px;
  width: 600px; height: 600px;
  background: radial-gradient(circle, rgba(0,173,216,0.12) 0%, transparent 70%);
  border-radius: 50%;
}
.hero-bg::after {
  content: '';
  position: absolute;
  bottom: -150px; left: -100px;
  width: 500px; height: 500px;
  background: radial-gradient(circle, rgba(0,173,216,0.08) 0%, transparent 70%);
  border-radius: 50%;
}

.hero-content {
  max-width: 860px;
  text-align: center;
  position: relative;
  z-index: 1;
}

.hero-badges {
  display: flex;
  justify-content: center;
  gap: 8px;
  flex-wrap: wrap;
  margin-bottom: 24px;
}
.hero-badges img { height: 24px; }

.hero-title {
  font-size: clamp(2.5rem, 6vw, 4.5rem);
  font-weight: 800;
  margin-bottom: 16px;
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: 4px;
}
.hero-dig {
  font-family: var(--font-mono);
  color: var(--go-cyan-dark);
  letter-spacing: -2px;
}
.hero-subtitle {
  font-size: clamp(1.1rem, 2.5vw, 1.6rem);
  font-weight: 400;
  color: var(--text-secondary);
}

.hero-tagline {
  font-size: clamp(0.95rem, 1.8vw, 1.15rem);
  color: var(--text-secondary);
  margin-bottom: 32px;
  line-height: 1.8;
}

.hero-cta { display: flex; gap: 16px; justify-content: center; margin-bottom: 48px; flex-wrap: wrap; }

.btn {
  display: inline-flex;
  align-items: center;
  padding: 12px 28px;
  border-radius: var(--radius-sm);
  font-size: 16px;
  font-weight: 600;
  transition: all 0.25s;
  cursor: pointer;
  border: 2px solid transparent;
}
.btn-primary {
  background: var(--go-cyan);
  color: white;
  box-shadow: 0 4px 14px rgba(0,173,216,0.35);
}
.btn-primary:hover {
  background: var(--go-cyan-dark);
  color: white;
  transform: translateY(-2px);
  box-shadow: 0 6px 20px rgba(0,173,216,0.45);
}
.btn-secondary {
  background: transparent;
  color: var(--go-dark);
  border-color: var(--border-color);
}
.btn-secondary:hover {
  border-color: var(--go-cyan);
  color: var(--go-cyan-dark);
  transform: translateY(-2px);
}

/* ===== Code Window ===== */
.hero-code-preview { max-width: 600px; margin: 0 auto; }

.code-window {
  background: var(--code-bg);
  border-radius: var(--radius);
  overflow: hidden;
  box-shadow: var(--shadow-lg);
  text-align: left;
}
.code-window.small { max-width: 100%; }

.code-window-bar {
  display: flex;
  align-items: center;
  gap: 6px;
  padding: 10px 16px;
  background: rgba(0,0,0,0.3);
  border-bottom: 1px solid rgba(255,255,255,0.08);
}
.dot { width: 12px; height: 12px; border-radius: 50%; }
.dot-red { background: #ff5f56; }
.dot-yellow { background: #ffbd2e; }
.dot-green { background: #27c93f; }
.code-window-title {
  margin-left: 8px;
  font-size: 13px;
  color: rgba(255,255,255,0.5);
  font-family: var(--font-mono);
}

.code-window pre {
  padding: 20px 24px;
  overflow-x: auto;
  font-size: 14px;
  line-height: 1.65;
}

/* Syntax highlight */
.c-keyword { color: #c678dd; }
.c-func { color: #61afef; }
.c-type { color: #e5c07b; }
.c-string { color: #98c379; }
.c-comment { color: #7f848e; font-style: italic; }
.c-number { color: #d19a66; }

/* ===== Sections ===== */
.section { padding: 80px 0; }
.section-alt { background: var(--bg-light); }

.section-title {
  font-size: clamp(1.8rem, 3.5vw, 2.4rem);
  font-weight: 700;
  text-align: center;
  margin-bottom: 12px;
}
.section-desc {
  text-align: center;
  color: var(--text-secondary);
  font-size: 1.05rem;
  margin-bottom: 48px;
  max-width: 600px;
  margin-left: auto;
  margin-right: auto;
}

.subsection-title {
  font-size: 1.4rem;
  font-weight: 700;
  margin: 48px 0 8px;
}

/* ===== Why Grid ===== */
.why-grid {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: 24px;
}
.why-card {
  background: var(--bg-white);
  border-radius: var(--radius);
  padding: 32px 24px;
  border: 2px solid var(--border-color);
  transition: transform 0.25s, box-shadow 0.25s;
}
.why-card:hover { transform: translateY(-4px); box-shadow: var(--shadow-md); }
.why-card-dig { border-color: var(--go-cyan); box-shadow: 0 0 0 1px var(--go-cyan); }

.why-card-header { margin-bottom: 20px; display: flex; align-items: center; gap: 8px; }
.why-badge {
  font-family: var(--font-mono);
  font-weight: 700;
  font-size: 14px;
  padding: 4px 12px;
  border-radius: 6px;
}
.why-badge-blue { background: #e3f2fd; color: #1976d2; }
.why-badge-orange { background: #fff3e0; color: #e65100; }
.why-badge-cyan { background: var(--go-cyan-light); color: var(--go-cyan-dark); }
.why-tag { font-size: 12px; color: var(--go-cyan-dark); font-weight: 600; }

.why-body { display: flex; flex-direction: column; gap: 12px; }
.why-pro, .why-con { display: flex; align-items: flex-start; gap: 8px; font-size: 14px; }
.why-icon { font-weight: 700; flex-shrink: 0; }
.why-pro .why-icon { color: #27c93f; }
.why-con .why-icon { color: #ff5f56; }

/* ===== Features Grid ===== */
.features-grid {
  display: grid;
  grid-template-columns: repeat(4, 1fr);
  gap: 20px;
}
.feature-card {
  background: var(--bg-white);
  border-radius: var(--radius);
  padding: 24px 20px;
  border: 1px solid var(--border-color);
  transition: transform 0.25s, box-shadow 0.25s, border-color 0.25s;
}
.feature-card:hover {
  transform: translateY(-4px);
  box-shadow: var(--shadow-md);
  border-color: var(--go-cyan);
}
.feature-icon { font-size: 28px; margin-bottom: 12px; }
.feature-card h3 { font-size: 16px; font-weight: 700; margin-bottom: 8px; }
.feature-card p { font-size: 14px; color: var(--text-secondary); line-height: 1.6; }

.constraint-block {
  background: var(--bg-white);
  border-radius: var(--radius);
  padding: 24px 20px;
  border: 1px solid var(--border-color);
  margin-bottom: 20px;
}
.constraint-block h3 { font-size: 16px; font-weight: 700; margin-bottom: 8px; }
.constraint-block p { font-size: 14px; color: var(--text-secondary); line-height: 1.6; }

/* ===== Quick Start ===== */
.quickstart-steps { max-width: 800px; margin: 0 auto; display: flex; flex-direction: column; gap: 32px; }
.qs-step { display: flex; gap: 20px; align-items: flex-start; }
.qs-number {
  width: 40px; height: 40px;
  background: var(--go-cyan);
  color: white;
  border-radius: 50%;
  display: flex;
  align-items: center;
  justify-content: center;
  font-size: 18px;
  font-weight: 700;
  flex-shrink: 0;
}
.qs-content { flex: 1; min-width: 0; }
.qs-content h3 { font-size: 18px; margin-bottom: 12px; }
.qs-content .code-window { margin-top: 4px; }

/* ===== API Grid ===== */
.api-grid {
  display: grid;
  grid-template-columns: repeat(2, 1fr);
  gap: 16px;
  margin-bottom: 40px;
}
.api-card {
  background: var(--bg-white);
  border-radius: var(--radius-sm);
  padding: 20px 24px;
  border: 1px solid var(--border-color);
  transition: border-color 0.25s;
}
.api-card:hover { border-color: var(--go-cyan); }
.api-signature {
  font-family: var(--font-mono);
  font-size: 14px;
  color: var(--text-primary);
  margin-bottom: 6px;
}
.api-name { color: var(--go-cyan-dark); font-weight: 700; }
.api-desc { font-size: 14px; color: var(--text-secondary); }

/* ===== Tables ===== */
.table-wrapper { overflow-x: auto; border-radius: var(--radius); box-shadow: var(--shadow-sm); margin-bottom: 24px; }
.data-table {
  width: 100%;
  border-collapse: collapse;
  background: var(--bg-white);
  font-size: 14px;
}
.data-table th, .data-table td {
  padding: 12px 16px;
  text-align: left;
  border-bottom: 1px solid var(--border-color);
}
.data-table th {
  background: var(--bg-alt);
  font-weight: 700;
  font-size: 13px;
  color: var(--text-primary);
  white-space: nowrap;
}
.data-table tbody tr:last-child td { border-bottom: none; }
.data-table tbody tr:hover { background: var(--bg-light); }
.data-table .col-dig { background: rgba(0,173,216,0.04); font-weight: 600; }
.comp-table th, .comp-table td { font-size: 13px; }

/* ===== Comparison Tabs ===== */
.comparison-tabs {
  display: flex;
  gap: 4px;
  justify-content: center;
  margin-bottom: 24px;
  flex-wrap: wrap;
}
.comp-tab {
  padding: 8px 20px;
  border: 2px solid var(--border-color);
  background: var(--bg-white);
  border-radius: var(--radius-sm);
  font-size: 14px;
  font-weight: 600;
  color: var(--text-secondary);
  cursor: pointer;
  transition: all 0.2s;
}
.comp-tab:hover { border-color: var(--go-cyan); color: var(--go-cyan-dark); }
.comp-tab.active { background: var(--go-cyan); border-color: var(--go-cyan); color: white; }

.comp-panel { display: none; }
.comp-panel.active { display: block; animation: fadeIn 0.3s; }

@keyframes fadeIn { from { opacity: 0; } to { opacity: 1; } }

/* ===== Examples ===== */
.examples-grid { display: grid; grid-template-columns: 1fr 1fr; gap: 32px; margin-bottom: 32px; }
.example-category h3 { font-size: 18px; margin-bottom: 16px; }
.example-list { list-style: none; display: flex; flex-direction: column; gap: 8px; }
.example-list li {
  padding: 10px 16px;
  background: var(--bg-white);
  border-radius: var(--radius-sm);
  border: 1px solid var(--border-color);
  font-size: 14px;
}
.example-list-fail li { border-color: #ffcdd2; }
.example-list strong { color: var(--go-cyan-dark); font-family: var(--font-mono); font-size: 13px; }
.examples-cta { text-align: center; }

/* ===== Timeline ===== */
.timeline { max-width: 760px; margin: 0 auto; position: relative; padding-left: 24px; }
.timeline::before {
  content: '';
  position: absolute;
  left: 7px; top: 8px; bottom: 8px;
  width: 2px;
  background: var(--border-color);
}
.timeline-item { position: relative; margin-bottom: 32px; padding-left: 32px; }
.timeline-item::before {
  content: '';
  position: absolute;
  left: 0; top: 4px;
  width: 16px; height: 16px;
  background: var(--go-cyan);
  border-radius: 50%;
  border: 3px solid white;
  box-shadow: 0 0 0 2px var(--go-cyan);
}
.timeline-version {
  font-family: var(--font-mono);
  font-weight: 700;
  color: var(--go-cyan-dark);
  font-size: 18px;
}
.timeline-date { font-size: 13px; color: var(--text-light); margin-bottom: 4px; }
.timeline-content h3 { font-size: 16px; margin-bottom: 4px; }
.timeline-content p { font-size: 14px; color: var(--text-secondary); }
.changelog-cta { text-align: center; margin-top: 16px; }

/* ===== Footer ===== */
footer {
  background: var(--go-dark);
  color: rgba(255,255,255,0.7);
  padding: 48px 0 24px;
}
.footer-content {
  display: flex;
  justify-content: space-between;
  gap: 48px;
  flex-wrap: wrap;
  margin-bottom: 32px;
}
.footer-brand .logo-icon { display: inline-block; margin-bottom: 8px; }
.footer-brand p { font-size: 14px; }
.footer-links { display: flex; gap: 48px; flex-wrap: wrap; }
.footer-col h4 { color: white; font-size: 14px; margin-bottom: 12px; }
.footer-col a {
  display: block;
  color: rgba(255,255,255,0.6);
  font-size: 14px;
  padding: 4px 0;
  transition: color 0.2s;
}
.footer-col a:hover { color: var(--go-cyan); }
.footer-bottom {
  border-top: 1px solid rgba(255,255,255,0.1);
  padding-top: 20px;
  text-align: center;
  font-size: 13px;
  color: rgba(255,255,255,0.4);
}
.footer-bottom a { color: rgba(255,255,255,0.6); }
.footer-bottom a:hover { color: var(--go-cyan); }

/* ===== Responsive ===== */
@media (max-width: 968px) {
  .features-grid { grid-template-columns: repeat(2, 1fr); }
  .why-grid { grid-template-columns: 1fr; }
  .api-grid { grid-template-columns: 1fr; }
  .examples-grid { grid-template-columns: 1fr; }
}

@media (max-width: 768px) {
  .nav-links { display: none; }
  .nav-links.active {
    display: flex;
    flex-direction: column;
    position: absolute;
    top: 64px; left: 0; right: 0;
    background: white;
    padding: 20px 24px;
    gap: 16px;
    border-bottom: 1px solid var(--border-color);
    box-shadow: var(--shadow-md);
  }
  .nav-toggle { display: flex; }
  .nav-toggle.active span:nth-child(1) { transform: rotate(45deg) translate(5px, 5px); }
  .nav-toggle.active span:nth-child(2) { opacity: 0; }
  .nav-toggle.active span:nth-child(3) { transform: rotate(-45deg) translate(5px, -5px); }

  .section { padding: 56px 0; }
  .hero-cta { flex-direction: column; align-items: center; }
  .btn { width: 100%; max-width: 280px; justify-content: center; }
  .footer-content { flex-direction: column; gap: 24px; }
  .footer-links { gap: 32px; }
}

@media (max-width: 480px) {
  .features-grid { grid-template-columns: 1fr; }
  .qs-step { flex-direction: column; gap: 12px; }
  .hero-badges img { height: 20px; }
}

/* ===== Copy button for code blocks ===== */
pre { position: relative; }
.copy-btn {
  position: absolute;
  top: 8px;
  right: 8px;
  font-family: var(--font-sans);
  font-size: 12px;
  line-height: 1;
  padding: 5px 9px;
  color: #fff;
  background: rgba(0, 0, 0, 0.35);
  border: 1px solid rgba(255, 255, 255, 0.2);
  border-radius: 6px;
  cursor: pointer;
  opacity: 0;
  transition: opacity 0.15s;
}
pre:hover .copy-btn,
.copy-btn:focus { opacity: 1; }
.copy-btn:hover { background: rgba(0, 0, 0, 0.5); }

/* ===== Theme toggle button ===== */
.theme-toggle {
  border: 1px solid var(--border-color);
  background: var(--bg-white);
  color: var(--text-secondary);
  border-radius: 8px;
  padding: 6px 10px;
  cursor: pointer;
  font-size: 15px;
  line-height: 1;
  margin-left: 12px;
  flex-shrink: 0;
  transition: color 0.2s, border-color 0.2s;
}
.theme-toggle:hover { color: var(--go-cyan-dark); border-color: var(--go-cyan); }

/* ===== Table of Contents (TOC) ===== */
.toc {
  position: fixed;
  left: 8px;
  top: 76px;
  width: 210px;
  max-height: calc(100vh - 92px);
  overflow-y: auto;
  padding: 16px 12px;
  display: none;
  z-index: 900;
}
@media (min-width: 1320px) { .toc { display: block; } }
.toc-search {
  width: 100%;
  padding: 6px 10px;
  border: 1px solid var(--border-color);
  border-radius: 8px;
  font-size: 13px;
  margin-bottom: 10px;
  background: var(--bg-white);
  color: var(--text-primary);
}
.toc-search:focus { outline: none; border-color: var(--go-cyan); }
#toc-nav { display: flex; flex-direction: column; gap: 2px; }
.toc-link {
  display: block;
  padding: 5px 10px;
  border-radius: 6px;
  color: var(--text-secondary);
  font-size: 13px;
  border-left: 2px solid transparent;
  transition: background 0.15s, color 0.15s;
}
.toc-link:hover { color: var(--go-cyan-dark); background: var(--bg-light); }
.toc-link.active {
  color: var(--go-cyan-dark);
  border-left-color: var(--go-cyan);
  background: var(--go-cyan-light);
  font-weight: 600;
}

/* ===== Dependency graph (inline SVG) ===== */
.graph-wrap { margin: 8px auto 24px; max-width: 680px; }
.dep-graph { width: 100%; height: auto; display: block; }
.dep-graph .dep-node rect {
  fill: var(--bg-white);
  stroke: var(--go-cyan);
  stroke-width: 1.5;
}
.dep-graph .dep-node.dep-root rect { fill: var(--go-cyan); stroke: var(--go-cyan); }
.dep-graph .dep-node text {
  fill: var(--text-primary);
  font: 600 13px var(--font-sans);
  text-anchor: middle;
}
.dep-graph .dep-node.dep-root text { fill: #fff; }
.dep-graph .edges line {
  stroke: var(--go-cyan-dark);
  stroke-width: 1.5;
  marker-end: url(#arrow);
}
.dep-graph .arrow-head { fill: var(--go-cyan-dark); }
.graph-note { text-align: center; color: var(--text-secondary); font-size: 14px; margin-bottom: 16px; }

/* ===== Dark mode (no-flash via data-theme + prefers-color-scheme) ===== */
@media (prefers-color-scheme: dark) {
  :root:not([data-theme="light"]) {
    --text-primary: #e6e6f0;
    --text-secondary: #b8bcc8;
    --text-light: #8a8f9c;
    --bg-white: #16171f;
    --bg-light: #1d1f2a;
    --bg-alt: #14151c;
    --border-color: #2c2f3a;
    --go-cyan-light: #0e2c34;
    --go-cyan-dark: #5fd6ea;
  }
}
[data-theme="dark"] {
  --text-primary: #e6e6f0;
  --text-secondary: #b8bcc8;
  --text-light: #8a8f9c;
  --bg-white: #16171f;
  --bg-light: #1d1f2a;
  --bg-alt: #14151c;
  --border-color: #2c2f3a;
  --go-cyan-light: #0e2c34;
  --go-cyan-dark: #5fd6ea;
}
[data-theme="dark"] #navbar { background: rgba(22, 23, 31, 0.95); }
[data-theme="dark"] a { color: #5fd6ea; }
[data-theme="dark"] a:hover { color: var(--go-cyan); }