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

:root {
  --bg: #0d0d0d;
  --bg-elevated: #161616;
  --bg-card: #1a1a1a;
  --bg-card-hover: #222222;
  --border: rgba(255, 255, 255, 0.08);
  --text: #f5f5f5;
  --text-muted: #888888;
  --text-light: #aaaaaa;
  --accent-start: #ff9f0a;
  --accent-end: #ff6b00;
  --accent-glow: rgba(255, 159, 10, 0.35);
  --radius: 16px;
  --radius-sm: 10px;
  --nav-height: 64px;
  --max-width: 1100px;
  --doc-width: 760px;
  --transition: 0.25s cubic-bezier(0.4, 0, 0.2, 1);
}

html {
  scroll-behavior: smooth;
  font-size: 16px;
  -webkit-font-smoothing: antialiased;
}

body {
  font-family: Inter, -apple-system, BlinkMacSystemFont, "Segoe UI",
    "PingFang SC", "Hiragino Sans GB", "Microsoft YaHei", sans-serif;
  background: var(--bg);
  color: var(--text-light);
  line-height: 1.7;
  font-weight: 300;
  overflow-x: hidden;
}

a { color: inherit; text-decoration: none; }

/* ── Geometric background ── */
.bg-grid {
  position: fixed;
  inset: 0;
  pointer-events: none;
  z-index: 0;
  background-image:
    linear-gradient(rgba(255, 255, 255, 0.03) 1px, transparent 1px),
    linear-gradient(90deg, rgba(255, 255, 255, 0.03) 1px, transparent 1px);
  background-size: 64px 64px;
  mask-image: radial-gradient(ellipse 80% 60% at 50% 0%, black 20%, transparent 70%);
}

.page { position: relative; z-index: 1; min-height: 100vh; display: flex; flex-direction: column; }

/* ── Navigation ── */
.nav {
  position: fixed;
  top: 0;
  left: 0;
  right: 0;
  height: var(--nav-height);
  z-index: 100;
  display: flex;
  align-items: center;
  justify-content: center;
  transition: background var(--transition), backdrop-filter var(--transition),
    border-color var(--transition);
  border-bottom: 1px solid transparent;
}

.nav.scrolled {
  background: rgba(13, 13, 13, 0.75);
  backdrop-filter: blur(16px);
  -webkit-backdrop-filter: blur(16px);
  border-bottom-color: var(--border);
}

.nav-inner {
  width: 100%;
  max-width: var(--max-width);
  padding: 0 1.5rem;
  display: flex;
  align-items: center;
  justify-content: space-between;
}

.logo {
  display: flex;
  align-items: center;
  gap: 0.6rem;
  font-weight: 600;
  font-size: 1rem;
  color: var(--text);
  letter-spacing: -0.02em;
}

.logo-icon {
  width: 28px;
  height: 28px;
  flex-shrink: 0;
  object-fit: contain;
  border-radius: 6px;
}

.nav-links {
  display: flex;
  align-items: center;
  gap: 2rem;
}

.nav-links a {
  font-size: 0.875rem;
  font-weight: 400;
  color: var(--text-muted);
  transition: color var(--transition);
}

.nav-links a:hover,
.nav-links a.active {
  color: var(--accent-start);
}

/* ── Section shared (index) ── */
.section {
  max-width: var(--max-width);
  margin: 0 auto;
  padding: 6rem 1.5rem;
  width: 100%;
}

.section-label {
  font-size: 0.75rem;
  font-weight: 500;
  letter-spacing: 0.12em;
  text-transform: uppercase;
  color: var(--accent-start);
  margin-bottom: 0.75rem;
}

.section-title {
  font-size: clamp(1.75rem, 4vw, 2.25rem);
  font-weight: 800;
  color: var(--text);
  letter-spacing: -0.03em;
  line-height: 1.2;
  margin-bottom: 3rem;
}

/* ── Hero ── */
.hero {
  min-height: 100vh;
  display: flex;
  align-items: center;
  padding-top: var(--nav-height);
  position: relative;
  overflow: hidden;
}

.hero-inner {
  max-width: var(--max-width);
  margin: 0 auto;
  padding: 4rem 1.5rem;
  width: 100%;
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 3rem;
  align-items: center;
}

.hero-text h1 {
  font-size: clamp(2.5rem, 6vw, 4rem);
  font-weight: 900;
  color: var(--text);
  letter-spacing: -0.04em;
  line-height: 1.1;
  margin-bottom: 1.25rem;
}

.hero-text p {
  font-size: 1.05rem;
  font-weight: 300;
  color: var(--text-muted);
  margin-bottom: 2.5rem;
}

.btn-gradient {
  display: inline-flex;
  align-items: center;
  gap: 0.5rem;
  padding: 0.85rem 1.75rem;
  border-radius: 999px;
  border: none;
  cursor: pointer;
  font-size: 0.95rem;
  font-weight: 500;
  color: #fff;
  background: linear-gradient(135deg, var(--accent-start), var(--accent-end));
  box-shadow: 0 4px 24px var(--accent-glow);
  transition: transform var(--transition), box-shadow var(--transition);
}

.btn-gradient:hover {
  transform: translateY(-2px);
  box-shadow: 0 8px 32px rgba(255, 107, 0, 0.45);
}

.hero-visual {
  position: relative;
  display: flex;
  align-items: center;
  justify-content: center;
  min-height: 360px;
}

/* Ambient glow behind screenshot */
.hero-glow {
  position: absolute;
  width: 320px;
  height: 320px;
  border-radius: 50%;
  background: radial-gradient(
    circle at 40% 35%,
    rgba(255, 159, 10, 0.55) 0%,
    rgba(255, 107, 0, 0.25) 40%,
    rgba(255, 107, 0, 0.06) 65%,
    transparent 75%
  );
  filter: blur(24px);
  animation: pulse 6s ease-in-out infinite;
  z-index: 0;
}

.hero-screenshot {
  position: relative;
  z-index: 1;
  width: 260px;
  margin: 0;
  border-radius: 32px;
  overflow: hidden;
  box-shadow:
    0 24px 64px rgba(0, 0, 0, 0.55),
    0 0 0 1px rgba(255, 255, 255, 0.08);
}

.hero-screenshot img {
  display: block;
  width: 100%;
  height: auto;
  vertical-align: middle;
}

.glow-ring {
  position: absolute;
  width: 400px;
  height: 400px;
  border-radius: 50%;
  border: 1px solid rgba(255, 159, 10, 0.12);
  animation: spin 20s linear infinite;
}

.glow-ring::before {
  content: "";
  position: absolute;
  inset: 30px;
  border-radius: 50%;
  border: 1px solid rgba(255, 159, 10, 0.06);
}

.glow-line {
  position: absolute;
  width: 1px;
  height: 200px;
  background: linear-gradient(to bottom, transparent, var(--accent-start), transparent);
  opacity: 0.3;
  transform: rotate(25deg);
}

@keyframes pulse {
  0%, 100% { transform: scale(1); opacity: 1; }
  50% { transform: scale(1.06); opacity: 0.85; }
}

@keyframes spin {
  from { transform: rotate(0deg); }
  to { transform: rotate(360deg); }
}

/* ── Features ── */
.features { background: var(--bg); }

.features-grid {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: 1.25rem;
}

.feature-card {
  background: var(--bg-card);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 2rem 1.75rem;
  transition: transform var(--transition), box-shadow var(--transition),
    background var(--transition), border-color var(--transition);
}

.feature-card:hover {
  transform: translateY(-4px);
  background: var(--bg-card-hover);
  border-color: rgba(255, 159, 10, 0.2);
  box-shadow: 0 12px 40px rgba(0, 0, 0, 0.4), 0 0 0 1px rgba(255, 159, 10, 0.08);
}

.feature-icon {
  width: 40px;
  height: 40px;
  border-radius: var(--radius-sm);
  background: linear-gradient(135deg, rgba(255, 159, 10, 0.15), rgba(255, 107, 0, 0.08));
  display: flex;
  align-items: center;
  justify-content: center;
  margin-bottom: 1.25rem;
  color: var(--accent-start);
}

.feature-icon svg { width: 20px; height: 20px; }

.feature-card h3 {
  font-size: 1rem;
  font-weight: 700;
  color: var(--text);
  margin-bottom: 0.5rem;
}

.feature-card p {
  font-size: 0.875rem;
  font-weight: 300;
  color: var(--text-muted);
  line-height: 1.65;
}

/* ── How to Use ── */
.howto { background: var(--bg-elevated); }

.steps {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: 1.25rem;
  position: relative;
}

.steps::before {
  content: "";
  position: absolute;
  top: 36px;
  left: calc(16.67% + 20px);
  right: calc(16.67% + 20px);
  height: 1px;
  background: linear-gradient(90deg, var(--accent-start), var(--accent-end));
  opacity: 0.3;
}

.step-card {
  background: var(--bg-card);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 2rem 1.75rem;
  text-align: center;
  transition: transform var(--transition), box-shadow var(--transition);
  position: relative;
}

.step-card:hover {
  transform: translateY(-3px);
  box-shadow: 0 8px 32px rgba(0, 0, 0, 0.35);
}

.step-num {
  width: 40px;
  height: 40px;
  border-radius: 50%;
  background: linear-gradient(135deg, var(--accent-start), var(--accent-end));
  color: #fff;
  font-size: 0.9rem;
  font-weight: 700;
  display: flex;
  align-items: center;
  justify-content: center;
  margin: 0 auto 1.25rem;
  position: relative;
  z-index: 1;
}

.step-card h3 {
  font-size: 1rem;
  font-weight: 700;
  color: var(--text);
  margin-bottom: 0.4rem;
}

.step-card p {
  font-size: 0.85rem;
  font-weight: 300;
  color: var(--text-muted);
}

/* ── Accordion ── */
.accordion {
  border: 1px solid var(--border);
  border-radius: var(--radius);
  overflow: hidden;
  background: var(--bg-card);
}

.accordion-trigger {
  width: 100%;
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding: 1.25rem 1.5rem;
  background: none;
  border: none;
  cursor: pointer;
  color: var(--text);
  font-family: inherit;
  font-size: 1rem;
  font-weight: 600;
  text-align: left;
  transition: background var(--transition);
}

.accordion-trigger:hover {
  background: rgba(255, 255, 255, 0.03);
}

.accordion-arrow {
  font-size: 0.85rem;
  color: var(--accent-start);
  transition: transform var(--transition);
  flex-shrink: 0;
  margin-left: 1rem;
}

.accordion.open .accordion-arrow {
  transform: rotate(90deg);
}

.accordion-body {
  max-height: 0;
  overflow: hidden;
  transition: max-height 0.4s cubic-bezier(0.4, 0, 0.2, 1);
}

.accordion-content {
  padding: 0 1.5rem 1.5rem;
  font-size: 0.9rem;
  font-weight: 300;
  color: var(--text-muted);
  line-height: 1.75;
}

.accordion-content a {
  color: var(--accent-start);
  transition: opacity var(--transition);
}

.accordion-content a:hover { opacity: 0.8; }

.privacy { background: var(--bg); }

.privacy-date {
  margin-top: 1.25rem;
  font-size: 0.8rem;
  color: var(--text-muted);
  opacity: 0.6;
}

/* ── Footer ── */
.footer {
  margin-top: auto;
  border-top: 1px solid var(--border);
  padding: 2rem 1.5rem;
  text-align: center;
}

.footer p {
  font-size: 0.8rem;
  font-weight: 300;
  color: var(--text-muted);
}

/* ── Document pages (guide & privacy) ── */
.doc-main {
  flex: 1;
  max-width: var(--doc-width);
  margin: 0 auto;
  padding: calc(var(--nav-height) + 3rem) 1.5rem 4rem;
  width: 100%;
}

.doc-header {
  margin-bottom: 2.5rem;
}

.doc-title {
  font-size: clamp(2rem, 5vw, 2.75rem);
  font-weight: 900;
  color: var(--text);
  letter-spacing: -0.04em;
  line-height: 1.15;
  margin-bottom: 0.75rem;
}

.doc-meta {
  font-size: 0.9rem;
  font-weight: 300;
  color: var(--text-muted);
  line-height: 1.6;
}

.doc-intro {
  font-size: 0.925rem;
  font-weight: 300;
  color: var(--text-light);
  margin-bottom: 2rem;
  line-height: 1.75;
}

.doc-intro p {
  margin-bottom: 0.75rem;
}

.doc-intro p:last-child {
  margin-bottom: 0;
}

.doc-body {
  display: flex;
  flex-direction: column;
  gap: 1rem;
}

.doc-section {
  background: var(--bg-card);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 1.75rem 2rem;
  transition: border-color var(--transition);
}

.doc-section:hover {
  border-color: rgba(255, 159, 10, 0.15);
}

.doc-section h2 {
  font-size: 1rem;
  font-weight: 700;
  color: var(--text);
  margin-bottom: 1rem;
  padding-left: 0.85rem;
  border-left: 3px solid;
  border-image: linear-gradient(to bottom, var(--accent-start), var(--accent-end)) 1;
  letter-spacing: -0.01em;
}

.doc-section h3 {
  font-size: 0.9rem;
  font-weight: 600;
  color: var(--text);
  margin: 1.25rem 0 0.5rem;
}

.doc-section p {
  font-size: 0.9rem;
  font-weight: 300;
  color: var(--text-muted);
  margin-bottom: 0.65rem;
  line-height: 1.75;
}

.doc-section p:last-child { margin-bottom: 0; }

.doc-section ul,
.doc-section ol {
  padding-left: 1.25rem;
  margin-bottom: 0.5rem;
}

.doc-section li {
  font-size: 0.9rem;
  font-weight: 300;
  color: var(--text-muted);
  margin-bottom: 0.45rem;
  line-height: 1.7;
}

.doc-section li strong {
  color: var(--text-light);
  font-weight: 500;
}

.doc-section a {
  color: var(--accent-start);
  transition: opacity var(--transition);
}

.doc-section a:hover { opacity: 0.8; }

/* Steps inline in guide section 2 */
.doc-steps {
  display: flex;
  flex-direction: column;
  gap: 0.75rem;
  margin-top: 0.5rem;
}

.doc-step-item {
  display: flex;
  gap: 1rem;
  align-items: flex-start;
  padding: 1rem 1.15rem;
  background: var(--bg-elevated);
  border-radius: var(--radius-sm);
  border: 1px solid var(--border);
  transition: transform var(--transition), border-color var(--transition);
}

.doc-step-item:hover {
  transform: translateX(4px);
  border-color: rgba(255, 159, 10, 0.2);
}

.doc-step-badge {
  flex-shrink: 0;
  width: 28px;
  height: 28px;
  border-radius: 50%;
  background: linear-gradient(135deg, var(--accent-start), var(--accent-end));
  color: #fff;
  font-size: 0.75rem;
  font-weight: 700;
  display: flex;
  align-items: center;
  justify-content: center;
}

.doc-step-text {
  font-size: 0.9rem;
  font-weight: 300;
  color: var(--text-muted);
  line-height: 1.65;
}

.doc-step-text strong {
  color: var(--text-light);
  font-weight: 500;
}

/* ── Responsive ── */
@media (max-width: 768px) {
  .nav-links { gap: 1.25rem; }
  .nav-links a { font-size: 0.8rem; }

  .hero-inner {
    grid-template-columns: 1fr;
    text-align: center;
    padding: 2rem 1.5rem 4rem;
  }

  .hero-visual { order: -1; min-height: 280px; }

  .hero-glow { width: 220px; height: 220px; }
  .hero-screenshot { width: 220px; border-radius: 28px; }
  .glow-ring { width: 280px; height: 280px; }

  .features-grid,
  .steps { grid-template-columns: 1fr; }

  .steps::before { display: none; }

  .section { padding: 4rem 1.5rem; }
  .section-title { margin-bottom: 2rem; }

  .doc-main { padding-top: calc(var(--nav-height) + 2rem); }
  .doc-section { padding: 1.35rem 1.25rem; }
}

@media (max-width: 480px) {
  .nav-links { gap: 0.85rem; }
}