:root {
  --primary: #2563eb;
  --primary-dark: #1d4ed8;
  --accent: #06b6d4;
  --bg: #f8fafc;
  --card-bg: #ffffff;
  --text: #1f2937;
  --muted: #64748b;
  --code-bg: #1e293b;
  --border: #e2e8f0;
  --radius: 12px;
  --shadow: 0 4px 6px -1px rgba(0, 0, 0, 0.1);
  --shadow-lg: 0 10px 15px -3px rgba(0, 0, 0, 0.1);
}

* {
  box-sizing: border-box;
}

html {
  scroll-behavior: smooth;
  min-height: 100%;
  background: linear-gradient(135deg, #667eea 0%, #764ba2 100%);
}

body {
  margin: 0 auto;
  max-width: 560px;
  min-height: 100vh;
  font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, "Helvetica Neue", Arial, "PingFang SC", "Microsoft YaHei", sans-serif;
  background: var(--bg);
  color: var(--text);
  line-height: 1.7;
  box-shadow: 0 0 40px rgba(0, 0, 0, 0.18);
}

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

a:hover {
  text-decoration: underline;
}

/* Navigation */
.navbar {
  position: sticky;
  top: 0;
  z-index: 100;
  background: rgba(255, 255, 255, 0.92);
  backdrop-filter: blur(10px);
  border-bottom: 1px solid var(--border);
}

.nav-container {
  max-width: 100%;
  margin: 0 auto;
  padding: 0 1.25rem;
  display: flex;
  align-items: center;
  justify-content: space-between;
  height: 64px;
}

.logo {
  font-weight: 700;
  font-size: 1.1rem;
  color: var(--text);
}

.nav-links {
  display: flex;
  gap: 1.5rem;
  list-style: none;
  margin: 0;
  padding: 0;
}

.nav-links a {
  color: var(--muted);
  font-weight: 500;
  font-size: 0.95rem;
}

.nav-links a:hover,
.nav-links a.active {
  color: var(--primary);
  text-decoration: none;
}

.nav-toggle {
  display: none;
  background: none;
  border: none;
  font-size: 1.5rem;
  cursor: pointer;
  color: var(--text);
}

/* Hero */
.hero {
  background: linear-gradient(135deg, var(--primary) 0%, #4f46e5 100%);
  color: #fff;
  padding: 3rem 1.25rem;
  text-align: center;
}

.hero h1 {
  margin: 0 0 1rem;
  font-size: 1.9rem;
  line-height: 1.3;
}

.hero p {
  margin: 0 auto 1.75rem;
  max-width: 480px;
  font-size: 1rem;
  opacity: 0.92;
}

.hero-actions {
  display: flex;
  flex-direction: column;
  gap: 0.75rem;
  align-items: stretch;
}

.hero-actions .btn {
  width: 100%;
}

/* Buttons */
.btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  padding: 0.75rem 1.5rem;
  border-radius: var(--radius);
  font-weight: 600;
  font-size: 1rem;
  transition: transform 0.1s, box-shadow 0.2s, background 0.2s;
  border: none;
  cursor: pointer;
}

.btn:hover {
  text-decoration: none;
  transform: translateY(-1px);
}

.btn-primary {
  background: #fff;
  color: var(--primary);
  box-shadow: var(--shadow);
}

.btn-primary:hover {
  background: #f1f5f9;
}

.btn-secondary {
  background: rgba(255, 255, 255, 0.15);
  color: #fff;
  border: 1px solid rgba(255, 255, 255, 0.4);
}

.btn-secondary:hover {
  background: rgba(255, 255, 255, 0.25);
}

.btn-disabled,
.btn-disabled:hover {
  background: #cbd5e1;
  color: #64748b;
  cursor: not-allowed;
  transform: none;
  box-shadow: none;
}

/* Layout */
.container {
  max-width: 100%;
  margin: 0 auto;
  padding: 2rem 1.25rem;
}

.section-title {
  font-size: 1.45rem;
  margin: 0 0 1rem;
  color: var(--text);
}

.lead {
  font-size: 1rem;
  color: var(--muted);
  margin-bottom: 1.5rem;
}

/* Cards */
.card-grid {
  display: grid;
  grid-template-columns: 1fr;
  gap: 1rem;
  margin-bottom: 2rem;
}

.card {
  background: var(--card-bg);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 1.25rem;
  box-shadow: var(--shadow);
}

.card h3 {
  margin: 0 0 0.5rem;
  font-size: 1.15rem;
  color: var(--primary-dark);
}

.card p {
  margin: 0;
  color: var(--muted);
  font-size: 0.95rem;
}

/* Article / Guide */
.article h2 {
  font-size: 1.35rem;
  margin-top: 2rem;
  margin-bottom: 0.9rem;
  padding-bottom: 0.4rem;
  border-bottom: 2px solid var(--border);
}

.article h3 {
  font-size: 1.2rem;
  margin-top: 1.75rem;
  margin-bottom: 0.75rem;
  color: var(--primary-dark);
}

.article ul,
.article ol {
  padding-left: 1.5rem;
}

.article li {
  margin-bottom: 0.5rem;
}

.article p {
  margin: 0.75rem 0;
}

/* Code blocks */
.code-block {
  position: relative;
  margin: 1rem 0;
}

.code-block pre {
  background: var(--code-bg);
  color: #e2e8f0;
  padding: 0.85rem 1rem;
  border-radius: var(--radius);
  overflow-x: auto;
  font-family: ui-monospace, SFMono-Regular, Menlo, Monaco, Consolas, monospace;
  font-size: 0.85rem;
  line-height: 1.5;
}

.code-block code {
  font-family: inherit;
}

.copy-btn {
  position: absolute;
  top: 0.6rem;
  right: 0.6rem;
  padding: 0.35rem 0.7rem;
  font-size: 0.8rem;
  background: rgba(255, 255, 255, 0.1);
  color: #e2e8f0;
  border: 1px solid rgba(255, 255, 255, 0.2);
  border-radius: 6px;
  cursor: pointer;
}

.copy-btn:hover {
  background: rgba(255, 255, 255, 0.2);
}

/* Info box */
.info-box {
  background: #eff6ff;
  border-left: 4px solid var(--primary);
  padding: 1rem 1.25rem;
  border-radius: 0 var(--radius) var(--radius) 0;
  margin: 1.25rem 0;
}

.info-box.warning {
  background: #fff7ed;
  border-left-color: #f59e0b;
}

/* Footer */
.site-footer {
  text-align: center;
  padding: 1.5rem 1.25rem;
  color: var(--muted);
  font-size: 0.85rem;
  border-top: 1px solid var(--border);
}

/* Responsive */
@media (max-width: 640px) {
  .nav-links {
    display: none;
    position: absolute;
    top: 64px;
    left: 0;
    right: 0;
    flex-direction: column;
    gap: 0;
    background: rgba(255, 255, 255, 0.98);
    border-bottom: 1px solid var(--border);
    padding: 0.5rem 0;
  }

  .nav-links.open {
    display: flex;
  }

  .nav-links li {
    width: 100%;
  }

  .nav-links a {
    display: block;
    padding: 0.75rem 1.5rem;
    border-bottom: 1px solid var(--border);
  }

  .nav-toggle {
    display: block;
  }

  .hero h1 {
    font-size: 1.75rem;
  }

  .hero p {
    font-size: 1rem;
  }
}