/* ===== Variables ===== */
:root {
  --color-sage-deep: #576153;
  --color-sage-soft: #84947E;
  --color-sage-muted: #E6ECE0;
  --color-paper: #F8F7F2;
  --color-card: #FFFEF9;
  --color-ink: #2C302E;
  --color-ink-secondary: #5A605C;
  --color-ink-tertiary: #8A908A;
  --color-amber: #C8943A;
  --color-amber-soft: #F5E6CC;
  --color-border: #E2E0D8;
  --color-focus: #C8943A;

  --font-stack: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, "Helvetica Neue", Arial, "PingFang SC", "Hiragino Sans GB", "Microsoft YaHei", sans-serif;

  --radius-sm: 8px;
  --radius-md: 8px;
  --radius-lg: 8px;
  --radius-xl: 8px;

  --space-xs: 0.5rem;
  --space-sm: 1rem;
  --space-md: 1.5rem;
  --space-lg: 2.5rem;
  --space-xl: 4rem;
  --space-2xl: 6rem;

  --container-max: 1120px;
  --container-padding: 1.5rem;

  --transition-fast: 150ms ease;
  --transition-base: 250ms ease;
}

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

html {
  scroll-behavior: smooth;
  -webkit-text-size-adjust: 100%;
}

@media (prefers-reduced-motion: reduce) {
  html {
    scroll-behavior: auto;
  }
  *, *::before, *::after {
    animation-duration: 0.01ms !important;
    animation-iteration-count: 1 !important;
    transition-duration: 0.01ms !important;
  }
}

body {
  font-family: var(--font-stack);
  font-size: 16px;
  line-height: 1.7;
  color: var(--color-ink);
  background-color: var(--color-paper);
  -webkit-font-smoothing: antialiased;
  -moz-osx-font-smoothing: grayscale;
}

img {
  max-width: 100%;
  height: auto;
  display: block;
}

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

ul, ol {
  list-style: none;
}

/* ===== Accessibility ===== */
.skip-link {
  position: absolute;
  top: -40px;
  left: 0;
  background: var(--color-ink);
  color: var(--color-card);
  padding: 0.5rem 1rem;
  z-index: 10000;
  border-radius: 0 0 var(--radius-sm) 0;
  font-size: 0.875rem;
}

.skip-link:focus {
  top: 0;
}

:focus-visible {
  outline: 2.5px solid var(--color-focus);
  outline-offset: 2px;
  border-radius: var(--radius-sm);
}

/* ===== Layout ===== */
.container {
  max-width: var(--container-max);
  margin-inline: auto;
  padding-inline: var(--container-padding);
}

.section-header {
  text-align: center;
  margin-bottom: var(--space-xl);
}

.section-title {
  font-size: 2.25rem;
  font-weight: 700;
  line-height: 1.25;
  color: var(--color-ink);
  margin-bottom: var(--space-sm);
}

.section-desc {
  font-size: 1.125rem;
  color: var(--color-ink-secondary);
  max-width: 520px;
  margin-inline: auto;
}

.section-lead {
  font-size: 1.125rem;
  color: var(--color-ink-secondary);
  margin-bottom: var(--space-md);
}

.section-note {
  font-size: 0.875rem;
  color: var(--color-ink-tertiary);
  margin-top: var(--space-md);
}

/* ===== Buttons ===== */
.btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  padding: 0.875rem 1.75rem;
  border-radius: 100px;
  font-size: 1rem;
  font-weight: 600;
  line-height: 1;
  cursor: pointer;
  border: 2px solid transparent;
  transition: background var(--transition-fast), border-color var(--transition-fast), transform var(--transition-fast);
}

.btn:active {
  transform: scale(0.98);
}

.btn-primary {
  background-color: var(--color-sage-deep);
  color: var(--color-card);
  border-color: var(--color-sage-deep);
}

.btn-primary:hover {
  background-color: var(--color-ink);
  border-color: var(--color-ink);
}

.btn-secondary {
  background-color: transparent;
  color: var(--color-sage-deep);
  border-color: var(--color-sage-deep);
}

.btn-secondary:hover {
  background-color: var(--color-sage-muted);
}

/* ===== Header ===== */
.site-header {
  position: sticky;
  top: 0;
  z-index: 1000;
  background: rgba(248, 247, 242, 0.92);
  backdrop-filter: saturate(180%) blur(16px);
  -webkit-backdrop-filter: saturate(180%) blur(16px);
  border-bottom: 1px solid var(--color-border);
}

.header-inner {
  display: flex;
  align-items: center;
  justify-content: space-between;
  height: 64px;
}

.brand {
  display: flex;
  align-items: center;
  gap: 0.625rem;
  font-weight: 700;
  font-size: 1.25rem;
  color: var(--color-ink);
}

.brand-logo {
  border-radius: var(--radius-sm);
}

.nav-list {
  display: flex;
  gap: 2rem;
}

.nav-list a {
  font-size: 0.9375rem;
  font-weight: 500;
  color: var(--color-ink-secondary);
  transition: color var(--transition-fast);
}

.nav-list a:hover {
  color: var(--color-ink);
}

.nav-toggle {
  display: none;
  width: 40px;
  height: 40px;
  background: none;
  border: none;
  cursor: pointer;
  position: relative;
}

.hamburger,
.hamburger::before,
.hamburger::after {
  display: block;
  width: 22px;
  height: 2px;
  background: var(--color-ink);
  border-radius: 2px;
  transition: transform var(--transition-base), opacity var(--transition-base);
}

.hamburger {
  position: relative;
}

.hamburger::before,
.hamburger::after {
  content: "";
  position: absolute;
  left: 0;
}

.hamburger::before {
  top: -7px;
}

.hamburger::after {
  top: 7px;
}

.nav-toggle[aria-expanded="true"] .hamburger {
  background: transparent;
}

.nav-toggle[aria-expanded="true"] .hamburger::before {
  top: 0;
  transform: rotate(45deg);
}

.nav-toggle[aria-expanded="true"] .hamburger::after {
  top: 0;
  transform: rotate(-45deg);
}

.mobile-nav {
  display: none;
  background: var(--color-card);
  border-bottom: 1px solid var(--color-border);
}

.mobile-nav[hidden] {
  display: none;
}

.mobile-nav:not([hidden]) {
  display: block;
}

.mobile-nav-list {
  padding: var(--space-sm) var(--container-padding);
  display: flex;
  flex-direction: column;
  gap: 0.25rem;
}

.mobile-nav-list a {
  display: block;
  padding: 0.625rem 0.75rem;
  font-size: 1rem;
  font-weight: 500;
  color: var(--color-ink);
  border-radius: var(--radius-sm);
}

.mobile-nav-list a:hover {
  background: var(--color-sage-muted);
}

/* ===== Hero ===== */
.hero {
  position: relative;
  padding-top: var(--space-2xl);
  padding-bottom: var(--space-2xl);
  background: var(--color-paper);
  overflow: hidden;
}

.hero::before {
  content: "";
  position: absolute;
  inset: 0;
  background: radial-gradient(ellipse at 20% 10%, var(--color-sage-muted) 0%, transparent 60%),
              radial-gradient(ellipse at 80% 90%, var(--color-amber-soft) 0%, transparent 50%);
  opacity: 0.6;
  pointer-events: none;
}

.hero-inner {
  position: relative;
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: var(--space-xl);
  align-items: center;
}

.hero-text {
  max-width: 520px;
}

.hero-title {
  font-size: 3.25rem;
  font-weight: 800;
  line-height: 1.15;
  color: var(--color-ink);
  margin-bottom: var(--space-md);
  letter-spacing: -0.02em;
}

.hero-subtitle {
  font-size: 1.125rem;
  color: var(--color-ink-secondary);
  margin-bottom: var(--space-lg);
  line-height: 1.7;
}

.hero-cta {
  display: flex;
  gap: var(--space-sm);
  flex-wrap: wrap;
}

.hero-visual {
  display: flex;
  justify-content: center;
}

.phone-mock {
  position: relative;
  width: 280px;
  border-radius: var(--radius-xl);
  overflow: hidden;
  box-shadow:
    0 2px 4px rgba(0,0,0,0.04),
    0 8px 24px rgba(0,0,0,0.06),
    0 24px 64px rgba(0,0,0,0.08);
  background: var(--color-card);
}

.phone-mock img {
  width: 100%;
  height: auto;
  object-fit: cover;
}

.phone-mock--small {
  width: 240px;
}

.hero-hint {
  position: absolute;
  bottom: var(--space-lg);
  left: 50%;
  transform: translateX(-50%);
}

.scroll-indicator {
  display: block;
  width: 24px;
  height: 40px;
  border: 2px solid var(--color-ink-tertiary);
  border-radius: 12px;
  position: relative;
}

.scroll-indicator::after {
  content: "";
  position: absolute;
  top: 6px;
  left: 50%;
  transform: translateX(-50%);
  width: 4px;
  height: 8px;
  background: var(--color-ink-tertiary);
  border-radius: 2px;
  animation: scroll-bounce 2s infinite;
}

@keyframes scroll-bounce {
  0%, 100% { transform: translateX(-50%) translateY(0); opacity: 1; }
  50% { transform: translateX(-50%) translateY(8px); opacity: 0.4; }
}

/* ===== Features ===== */
.features {
  padding: var(--space-2xl) 0;
  background: var(--color-card);
}

.features-grid {
  display: grid;
  grid-template-columns: repeat(4, 1fr);
  gap: var(--space-md);
}

.feature-card {
  padding: var(--space-lg) var(--space-md);
  border-radius: var(--radius-md);
  background: var(--color-paper);
  transition: transform var(--transition-base), box-shadow var(--transition-base);
}

.feature-card:hover {
  transform: translateY(-4px);
  box-shadow: 0 12px 32px rgba(0,0,0,0.06);
}

.feature-icon {
  color: var(--color-sage-deep);
  margin-bottom: var(--space-md);
}

.feature-title {
  font-size: 1.125rem;
  font-weight: 700;
  margin-bottom: var(--space-xs);
  color: var(--color-ink);
}

.feature-desc {
  font-size: 0.9375rem;
  color: var(--color-ink-secondary);
  line-height: 1.7;
}

/* ===== AI Explanation ===== */
.ai-explanation {
  padding: var(--space-2xl) 0;
  background: var(--color-paper);
}

.ai-explanation-inner {
  display: grid;
  grid-template-columns: 1.2fr 1fr;
  gap: var(--space-xl);
  align-items: center;
}

.ai-boundary-list {
  display: flex;
  flex-direction: column;
  gap: var(--space-md);
  margin-top: var(--space-md);
}

.ai-boundary-list li {
  display: flex;
  flex-direction: column;
  gap: 0.25rem;
  padding: var(--space-md);
  background: var(--color-card);
  border-radius: var(--radius-md);
  border-left: 4px solid var(--color-sage-soft);
}

.ai-boundary-list li:last-child {
  border-left-color: var(--color-amber);
}

.boundary-yes {
  color: var(--color-sage-deep);
  font-weight: 700;
  font-size: 1rem;
}

.boundary-no {
  color: var(--color-amber);
  font-weight: 700;
  font-size: 1rem;
}

.ai-boundary-list span {
  font-size: 0.9375rem;
  color: var(--color-ink-secondary);
  line-height: 1.7;
}

.ai-explanation-visual {
  display: flex;
  justify-content: center;
}

/* ===== Screenshots ===== */
.screenshots {
  padding: var(--space-2xl) 0;
  background: var(--color-card);
}

.screenshots-grid {
  display: grid;
  grid-template-columns: repeat(4, 1fr);
  gap: var(--space-md);
}

.screenshot-item {
  text-align: center;
}

.screenshot-frame {
  border-radius: var(--radius-md);
  overflow: hidden;
  box-shadow: 0 4px 16px rgba(0,0,0,0.06);
  background: var(--color-paper);
  margin-bottom: var(--space-sm);
  transition: transform var(--transition-base), box-shadow var(--transition-base);
}

.screenshot-frame:hover {
  transform: translateY(-4px);
  box-shadow: 0 16px 40px rgba(0,0,0,0.08);
}

.screenshot-frame img {
  width: 100%;
  height: auto;
}

.screenshot-item figcaption {
  font-size: 0.875rem;
  font-weight: 500;
  color: var(--color-ink-secondary);
}

/* ===== Pricing ===== */
.pricing {
  padding: var(--space-2xl) 0;
  background: var(--color-paper);
}

.pricing-grid {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: var(--space-md);
  max-width: 800px;
  margin-inline: auto;
}

.pricing-card {
  position: relative;
  padding: var(--space-lg) var(--space-md);
  background: var(--color-card);
  border-radius: var(--radius-md);
  text-align: center;
  border: 1.5px solid var(--color-border);
  transition: transform var(--transition-base), box-shadow var(--transition-base), border-color var(--transition-base);
}

.pricing-card:hover {
  transform: translateY(-4px);
  box-shadow: 0 16px 40px rgba(0,0,0,0.08);
}

.pricing-card--featured {
  border-color: var(--color-sage-soft);
  box-shadow: 0 8px 24px rgba(87, 97, 83, 0.08);
}

.pricing-badge {
  position: absolute;
  top: -12px;
  left: 50%;
  transform: translateX(-50%);
  background: var(--color-sage-deep);
  color: var(--color-card);
  font-size: 0.75rem;
  font-weight: 700;
  padding: 0.25rem 0.875rem;
  border-radius: 100px;
  letter-spacing: 0.02em;
}

.pricing-name {
  font-size: 1.125rem;
  font-weight: 700;
  color: var(--color-ink);
  margin-bottom: var(--space-xs);
}

.pricing-price {
  font-size: 2.5rem;
  font-weight: 800;
  color: var(--color-sage-deep);
  line-height: 1.2;
  margin-bottom: var(--space-sm);
}

.pricing-unit {
  font-size: 1rem;
  font-weight: 500;
  color: var(--color-ink-tertiary);
}

.pricing-desc {
  font-size: 0.9375rem;
  color: var(--color-ink-secondary);
  line-height: 1.6;
}

.pricing-note {
  max-width: 640px;
  margin-inline: auto;
  margin-top: var(--space-lg);
  text-align: center;
  font-size: 0.875rem;
  color: var(--color-ink-tertiary);
  line-height: 1.7;
}

/* ===== FAQ ===== */
.faq {
  padding: var(--space-2xl) 0;
  background: var(--color-card);
}

.faq-list {
  max-width: 720px;
  margin-inline: auto;
  display: flex;
  flex-direction: column;
  gap: 0.75rem;
}

.faq-item {
  background: var(--color-paper);
  border-radius: var(--radius-md);
  border: 1px solid var(--color-border);
  overflow: hidden;
}

.faq-question {
  display: flex;
  align-items: center;
  justify-content: space-between;
  width: 100%;
  padding: var(--space-md);
  font-size: 1rem;
  font-weight: 600;
  color: var(--color-ink);
  cursor: pointer;
  list-style: none;
  transition: background var(--transition-fast);
}

.faq-question:hover {
  background: var(--color-sage-muted);
}

.faq-question::-webkit-details-marker {
  display: none;
}

.faq-question::after {
  content: "+";
  font-size: 1.25rem;
  font-weight: 400;
  color: var(--color-ink-tertiary);
  flex-shrink: 0;
  margin-left: var(--space-sm);
  transition: transform var(--transition-base);
}

.faq-item[open] .faq-question::after {
  content: "−";
  transform: rotate(0deg);
}

.faq-answer {
  padding: 0 var(--space-md) var(--space-md);
  font-size: 0.9375rem;
  color: var(--color-ink-secondary);
  line-height: 1.7;
}

/* ===== Footer ===== */
.site-footer {
  padding: var(--space-xl) 0 var(--space-lg);
  background: var(--color-ink);
  color: var(--color-sage-muted);
}

.footer-inner {
  display: flex;
  flex-direction: column;
  align-items: center;
  text-align: center;
  gap: var(--space-md);
}

.footer-brand {
  display: flex;
  align-items: center;
  gap: 0.5rem;
  color: var(--color-card);
  font-weight: 700;
  font-size: 1.125rem;
}

.footer-logo {
  border-radius: var(--radius-sm);
}

.footer-nav-list {
  display: flex;
  gap: 1.5rem;
  flex-wrap: wrap;
  justify-content: center;
}

.footer-nav-list a {
  font-size: 0.9375rem;
  color: var(--color-sage-muted);
  transition: color var(--transition-fast);
}

.footer-nav-list a:hover {
  color: var(--color-card);
}

.footer-disclaimer {
  font-size: 0.8125rem;
  color: var(--color-ink-tertiary);
  max-width: 600px;
  line-height: 1.6;
}

.footer-copyright {
  font-size: 0.8125rem;
  color: var(--color-ink-tertiary);
}

/* ===== Responsive ===== */
@media (max-width: 960px) {
  .hero-inner {
    grid-template-columns: 1fr;
    text-align: center;
  }

  .hero-text {
    max-width: 600px;
    margin-inline: auto;
  }

  .hero-cta {
    justify-content: center;
  }

  .hero-visual {
    order: -1;
  }

  .phone-mock {
    width: 240px;
  }

  .features-grid {
    grid-template-columns: repeat(2, 1fr);
  }

  .ai-explanation-inner {
    grid-template-columns: 1fr;
    text-align: center;
  }

  .ai-explanation-visual {
    order: -1;
  }

  .ai-boundary-list {
    text-align: left;
  }

  .screenshots-grid {
    grid-template-columns: repeat(2, 1fr);
  }
}

@media (max-width: 640px) {
  :root {
    --container-padding: 1rem;
  }

  .nav-list {
    display: none;
  }

  .nav-toggle {
    display: flex;
    align-items: center;
    justify-content: center;
  }

  .hero {
    padding-top: var(--space-xl);
    padding-bottom: var(--space-xl);
  }

  .hero-title {
    font-size: 2rem;
  }

  .hero-cta {
    flex-direction: column;
    align-items: stretch;
  }

  .btn {
    width: 100%;
  }

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

  .feature-card {
    padding: var(--space-md);
  }

  .screenshots-grid {
    grid-template-columns: 1fr;
  }

  .pricing-grid {
    grid-template-columns: 1fr;
    max-width: 360px;
  }

  .pricing-card--featured {
    order: -1;
  }

  .scroll-indicator {
    display: none;
  }
}

@media (max-width: 400px) {
  .phone-mock {
    width: 200px;
  }

  .section-title {
    font-size: 1.5rem;
  }

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