:root {
  --primary: #6366f1;
  --primary-hover: #4f46e5;
  --primary-light: #eef2ff;
  --accent: #06b6d4;
  --accent-light: #ecfeff;
  --success: #10b981;
  --warning: #f59e0b;
  --danger: #ef4444;
  --bg: #ffffff;
  --bg-soft: #f8fafc;
  --text: #1e293b;
  --text-muted: #64748b;
  --text-light: #94a3b8;
  --border: #e2e8f0;
  --border-light: #f1f5f9;
  --max-width: 780px;
  --radius: 12px;
  --shadow-sm: 0 1px 3px rgba(0,0,0,0.06);
  --shadow-md: 0 4px 16px rgba(0,0,0,0.08);
  --shadow-lg: 0 8px 30px rgba(0,0,0,0.12);
  --gradient: linear-gradient(135deg, #6366f1 0%, #06b6d4 100%);
}

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

body {
  font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, Helvetica, Arial, sans-serif, "Apple Color Emoji", "Segoe UI Emoji";
  line-height: 1.7;
  color: var(--text);
  background-color: var(--bg);
  -webkit-font-smoothing: antialiased;
}

/* ─── Header ───────────────────────────────────────── */

header {
  border-bottom: 1px solid var(--border);
  position: sticky;
  top: 0;
  background: rgba(255, 255, 255, 0.85);
  backdrop-filter: blur(12px);
  -webkit-backdrop-filter: blur(12px);
  z-index: 100;
}

.nav-container {
  max-width: var(--max-width);
  margin: 0 auto;
  padding: 0.875rem 1.25rem;
  display: flex;
  justify-content: space-between;
  align-items: center;
}

.logo {
  font-weight: 700;
  font-size: 1.15rem;
  color: var(--primary);
  text-decoration: none;
  display: flex;
  align-items: center;
  gap: 0.5rem;
}

.nav-links {
  display: flex;
  gap: 1.25rem;
}

.nav-links a {
  text-decoration: none;
  color: var(--text-muted);
  font-size: 0.9rem;
  font-weight: 500;
  transition: color 0.2s;
}

.nav-links a:hover {
  color: var(--primary);
}

/* ─── Main ─────────────────────────────────────────── */

main {
  max-width: var(--max-width);
  margin: 0 auto;
  padding: 2rem 1.25rem 4rem;
}

/* ─── Typography ───────────────────────────────────── */

h1 {
  font-size: 2rem;
  margin-bottom: 1rem;
  color: #0f172a;
  line-height: 1.3;
}

h2 {
  font-size: 1.4rem;
  margin: 2.5rem 0 0.75rem;
  color: #0f172a;
}

h3 {
  font-size: 1.15rem;
  margin: 1.5rem 0 0.5rem;
  color: var(--text);
}

p {
  margin-bottom: 1rem;
}

ul, ol {
  margin: 0.5rem 0 1rem 1.5rem;
}

li {
  margin-bottom: 0.4rem;
}

strong {
  color: #0f172a;
}

/* ─── Hero Section ─────────────────────────────────── */

.hero {
  text-align: center;
  padding: 3.5rem 0 2rem;
}

.hero h1 {
  font-size: 2.75rem;
  margin-bottom: 0.5rem;
  background: var(--gradient);
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
  background-clip: text;
}

.tagline {
  font-size: 1.3rem;
  color: var(--text-muted);
  margin-bottom: 0.5rem;
  font-weight: 500;
}

.sub-tagline {
  font-size: 0.95rem;
  color: var(--text-light);
  margin-bottom: 2rem;
}

.cta {
  display: flex;
  justify-content: center;
  gap: 0.75rem;
  flex-wrap: wrap;
}

.btn {
  display: inline-flex;
  align-items: center;
  gap: 0.4rem;
  background: var(--primary);
  color: white;
  padding: 0.7rem 1.6rem;
  border-radius: 9999px;
  text-decoration: none;
  font-weight: 600;
  font-size: 0.95rem;
  transition: all 0.25s;
  box-shadow: 0 2px 8px rgba(99, 102, 241, 0.25);
}

.btn:hover {
  background: var(--primary-hover);
  transform: translateY(-1px);
  box-shadow: 0 4px 14px rgba(99, 102, 241, 0.35);
}

.btn-outline {
  background: white;
  color: var(--primary);
  border: 1.5px solid var(--primary);
  box-shadow: none;
}

.btn-outline:hover {
  background: var(--primary-light);
  transform: translateY(-1px);
  box-shadow: var(--shadow-sm);
}

/* ─── Steps Section (三阶段流程) ──────────────────── */

.steps-section {
  padding: 2rem 0;
}

.steps-section h2 {
  text-align: center;
  margin-bottom: 0.5rem;
}

.steps-section .section-desc {
  text-align: center;
  color: var(--text-muted);
  margin-bottom: 2rem;
}

.step-flow {
  display: grid;
  grid-template-columns: 1fr;
  gap: 1rem;
}

@media (min-width: 640px) {
  .step-flow {
    grid-template-columns: repeat(3, 1fr);
    gap: 0;
  }
}

.step-item {
  position: relative;
  text-align: center;
  padding: 1.5rem 1.25rem;
  border-radius: var(--radius);
  background: var(--bg-soft);
  border: 1px solid var(--border-light);
  transition: all 0.3s;
}

@media (min-width: 640px) {
  .step-item {
    border-radius: 0;
    border-right: 1px solid var(--border);
  }
  .step-item:first-child {
    border-radius: var(--radius) 0 0 var(--radius);
  }
  .step-item:last-child {
    border-radius: 0 var(--radius) var(--radius) 0;
    border-right: 1px solid var(--border-light);
  }
}

.step-item:hover {
  background: var(--primary-light);
}

.step-num {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  width: 2.5rem;
  height: 2.5rem;
  border-radius: 50%;
  background: var(--gradient);
  color: white;
  font-weight: 700;
  font-size: 1.1rem;
  margin-bottom: 0.75rem;
}

.step-item h3 {
  margin: 0 0 0.5rem;
  font-size: 1.05rem;
  color: var(--primary);
}

.step-item p {
  font-size: 0.88rem;
  color: var(--text-muted);
  margin: 0;
  line-height: 1.5;
}

/* ─── Feature Cards ────────────────────────────────── */

.features {
  padding: 1rem 0 0;
}

.features h2 {
  text-align: center;
  margin-bottom: 1.5rem;
}

.card-grid {
  display: grid;
  grid-template-columns: 1fr;
  gap: 1rem;
  margin-top: 0;
}

@media (min-width: 640px) {
  .card-grid {
    grid-template-columns: 1fr 1fr;
  }
}

.card {
  border: 1px solid var(--border);
  padding: 1.35rem;
  border-radius: var(--radius);
  transition: transform 0.25s, box-shadow 0.25s;
  background: white;
}

.card:hover {
  transform: translateY(-3px);
  box-shadow: var(--shadow-md);
}

.card-icon {
  font-size: 1.5rem;
  margin-bottom: 0.5rem;
}

.card h3 {
  margin: 0 0 0.4rem;
  font-size: 1rem;
  color: var(--primary);
}

.card p {
  font-size: 0.9rem;
  color: var(--text-muted);
  margin: 0;
  line-height: 1.55;
}

/* ─── Help List ────────────────────────────────────── */

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

.help-list li {
  margin-bottom: 0.6rem;
}

.help-list a {
  font-size: 1rem;
  font-weight: 500;
  color: var(--text);
  text-decoration: none;
  display: flex;
  align-items: center;
  gap: 0.6rem;
  padding: 0.9rem 1.1rem;
  border: 1px solid var(--border);
  border-radius: var(--radius);
  transition: all 0.2s;
}

.help-list a:hover {
  border-color: var(--primary);
  background: var(--primary-light);
  color: var(--primary);
}

.help-list .help-emoji {
  font-size: 1.25rem;
  flex-shrink: 0;
}

/* ─── Help Article Content ─────────────────────────── */

.article-breadcrumb {
  font-size: 0.85rem;
  color: var(--text-muted);
  margin-bottom: 1.5rem;
}

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

.article-breadcrumb a:hover {
  text-decoration: underline;
}

.info-box {
  padding: 1rem 1.25rem;
  border-radius: var(--radius);
  margin: 1.5rem 0;
  font-size: 0.92rem;
  line-height: 1.6;
}

.info-box.tip {
  background: #f0fdf4;
  border: 1px solid #bbf7d0;
  color: #166534;
}

.info-box.warning {
  background: #fffbeb;
  border: 1px solid #fde68a;
  color: #92400e;
}

.info-box.info {
  background: var(--primary-light);
  border: 1px solid #c7d2fe;
  color: #3730a3;
}

/* ─── Feature Table ────────────────────────────────── */

.feature-table {
  width: 100%;
  border-collapse: collapse;
  margin: 1rem 0 1.5rem;
  font-size: 0.9rem;
}

.feature-table th,
.feature-table td {
  padding: 0.65rem 0.85rem;
  text-align: left;
  border-bottom: 1px solid var(--border);
}

.feature-table th {
  background: var(--bg-soft);
  font-weight: 600;
  color: #0f172a;
  font-size: 0.85rem;
  text-transform: none;
}

.feature-table tr:last-child td {
  border-bottom: none;
}

.feature-table tr:hover td {
  background: var(--bg-soft);
}

/* ─── FAQ ──────────────────────────────────────────── */

.faq-item {
  border: 1px solid var(--border);
  border-radius: var(--radius);
  margin-bottom: 0.75rem;
  overflow: hidden;
}

.faq-question {
  display: flex;
  justify-content: space-between;
  align-items: center;
  padding: 1rem 1.25rem;
  cursor: pointer;
  font-weight: 600;
  font-size: 0.95rem;
  background: white;
  transition: background 0.2s;
  user-select: none;
  border: none;
  width: 100%;
  text-align: left;
  color: var(--text);
}

.faq-question:hover {
  background: var(--bg-soft);
}

.faq-question::after {
  content: "＋";
  font-size: 1.1rem;
  color: var(--text-muted);
  transition: transform 0.3s;
  flex-shrink: 0;
}

.faq-item.open .faq-question::after {
  content: "－";
}

.faq-answer {
  display: none;
  padding: 0 1.25rem 1.1rem;
  color: var(--text-muted);
  font-size: 0.92rem;
  line-height: 1.7;
}

.faq-item.open .faq-answer {
  display: block;
}

/* ─── Pre / Code ───────────────────────────────────── */

pre {
  background: var(--bg-soft);
  padding: 1rem;
  border-radius: var(--radius);
  border: 1px solid var(--border);
  white-space: pre-wrap;
  font-family: "SF Mono", "Fira Code", "Cascadia Code", monospace;
  font-size: 0.88rem;
  margin: 1.25rem 0;
  overflow-x: auto;
}

code {
  font-family: "SF Mono", "Fira Code", "Cascadia Code", monospace;
  font-size: 0.88em;
  background: var(--bg-soft);
  padding: 0.15em 0.4em;
  border-radius: 4px;
}

/* ─── Footer ───────────────────────────────────────── */

footer {
  border-top: 1px solid var(--border);
  padding: 2rem 1.25rem;
  text-align: center;
  color: var(--text-muted);
  font-size: 0.85rem;
}

.footer-links {
  margin-bottom: 0.75rem;
  display: flex;
  justify-content: center;
  gap: 1rem;
  flex-wrap: wrap;
}

.footer-links a {
  color: var(--text-muted);
  text-decoration: none;
  transition: color 0.2s;
}

.footer-links a:hover {
  color: var(--primary);
}

/* ─── Mobile Adjustments ───────────────────────────── */

@media (max-width: 480px) {
  .logo span { display: none; }
  .logo::after { content: "刻忆"; }
  .hero h1 { font-size: 2rem; }
  .tagline { font-size: 1.1rem; }
  .step-flow { gap: 0.75rem; }
}