/* ================================================
   Keetch · 语刻 — Landing Page Styles
   Brand: Deep blue education + Emerald growth accent
   ================================================ */

/* ── CSS Custom Properties ── */
:root {
  /* Brand colors */
  --color-primary: #1E3A5F;
  --color-primary-light: #3B82F6;
  --color-primary-dark: #0F172A;
  --color-accent: #059669;
  --color-accent-hover: #047857;

  /* Surfaces */
  --surface: #FFFFFF;
  --surface-muted: #F8FAFC;
  --surface-card: #FFFFFF;

  /* Text */
  --text-primary: #0F172A;
  --text-secondary: #475569;
  --text-muted: #94A3B8;
  --text-on-dark: #F1F5F9;

  /* Borders & shadows */
  --border: #E2E8F0;
  --shadow-sm: 0 1px 2px rgba(15, 23, 42, 0.06);
  --shadow-md: 0 4px 6px -1px rgba(15, 23, 42, 0.08), 0 2px 4px -2px rgba(15, 23, 42, 0.05);
  --shadow-lg: 0 10px 15px -3px rgba(15, 23, 42, 0.08), 0 4px 6px -4px rgba(15, 23, 42, 0.04);

  /* Typography */
  --font-sans: "Inter", "Noto Sans SC", system-ui, -apple-system, sans-serif;

  /* Spacing */
  --section-py: clamp(4rem, 10vw, 8rem);
  --container-max: 1200px;
  --container-px: clamp(1.25rem, 5vw, 2.5rem);

  /* Transitions */
  --ease-out: cubic-bezier(0.33, 1, 0.68, 1);
  --duration-fast: 200ms;
  --duration-normal: 350ms;
}

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

html {
  scroll-behavior: smooth;
  -webkit-font-smoothing: antialiased;
  -moz-osx-font-smoothing: grayscale;
}

body {
  font-family: var(--font-sans);
  font-size: 1rem;
  line-height: 1.6;
  color: var(--text-primary);
  background: var(--surface);
}

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

a {
  color: var(--color-primary-light);
  text-decoration: none;
  transition: color var(--duration-fast) var(--ease-out);
}
a:hover {
  color: var(--color-primary);
}

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

/* ── Section ── */
.section {
  padding: var(--section-py) 0;
}
.section-muted {
  background: var(--surface-muted);
}

.section-label {
  display: inline-block;
  font-size: 0.875rem;
  font-weight: 600;
  letter-spacing: 0.05em;
  text-transform: uppercase;
  color: var(--color-primary-light);
  margin-bottom: 0.75rem;
}

.section-title {
  font-size: clamp(1.75rem, 4vw, 2.5rem);
  font-weight: 700;
  line-height: 1.25;
  color: var(--text-primary);
  margin-bottom: 1rem;
}

.section-desc {
  font-size: clamp(1rem, 2vw, 1.125rem);
  color: var(--text-secondary);
  max-width: 600px;
  margin: 0 auto 3rem;
  text-align: center;
}

.section-header {
  text-align: center;
  margin-bottom: 4rem;
}

/* ── Buttons ── */
.btn {
  display: inline-flex;
  align-items: center;
  gap: 0.5rem;
  padding: 0.75rem 1.75rem;
  font-family: var(--font-sans);
  font-size: 1rem;
  font-weight: 600;
  line-height: 1.4;
  border: 2px solid transparent;
  border-radius: 12px;
  cursor: pointer;
  transition: all var(--duration-fast) var(--ease-out);
  text-decoration: none;
  white-space: nowrap;
}

.btn-primary {
  background: var(--color-accent);
  color: #FFFFFF;
  border-color: var(--color-accent);
  box-shadow: var(--shadow-sm);
}
.btn-primary:hover {
  background: var(--color-accent-hover);
  border-color: var(--color-accent-hover);
  color: #FFFFFF;
  box-shadow: var(--shadow-md);
  transform: translateY(-1px);
}

.btn-outline {
  background: transparent;
  color: var(--text-on-dark);
  border-color: rgba(255, 255, 255, 0.3);
}
.btn-outline:hover {
  background: rgba(255, 255, 255, 0.1);
  border-color: rgba(255, 255, 255, 0.6);
  color: #FFFFFF;
}

.btn-outline-dark {
  background: transparent;
  color: var(--text-primary);
  border-color: var(--border);
}
.btn-outline-dark:hover {
  border-color: var(--color-primary-light);
  color: var(--color-primary-light);
}

.btn .icon {
  width: 20px;
  height: 20px;
  flex-shrink: 0;
}

.btn-lg {
  padding: 1rem 2.25rem;
  font-size: 1.125rem;
  border-radius: 14px;
}
.btn-lg .icon {
  width: 24px;
  height: 24px;
}

/* ── Header / Nav ── */
.header {
  position: fixed;
  top: 0;
  left: 0;
  right: 0;
  z-index: 100;
  background: rgba(255, 255, 255, 0.85);
  backdrop-filter: blur(12px);
  -webkit-backdrop-filter: blur(12px);
  border-bottom: 1px solid rgba(226, 232, 240, 0.5);
  transition: background var(--duration-normal) var(--ease-out);
}

.header-inner {
  display: flex;
  align-items: center;
  justify-content: space-between;
  height: 64px;
  max-width: var(--container-max);
  margin: 0 auto;
  padding: 0 var(--container-px);
}

.header-logo {
  display: flex;
  align-items: center;
  gap: 0.625rem;
  font-size: 1.125rem;
  font-weight: 700;
  color: var(--text-primary);
  text-decoration: none;
}
.header-logo:hover {
  color: var(--text-primary);
}
.header-logo img,
.header-logo svg {
  width: 32px;
  height: 32px;
  border-radius: 8px;
}

.header-nav {
  display: flex;
  align-items: center;
  gap: 0.75rem;
}

.header .btn {
  padding: 0.5rem 1.25rem;
  font-size: 0.875rem;
  border-radius: 10px;
}

/* ── Hero ── */
.hero {
  min-height: 100vh;
  display: flex;
  align-items: center;
  background: linear-gradient(135deg, var(--color-primary) 0%, var(--color-primary-dark) 100%);
  color: var(--text-on-dark);
  padding: 6rem 0 4rem;
  position: relative;
  overflow: hidden;
}

/* subtle decorative circle */
.hero::before {
  content: '';
  position: absolute;
  width: 600px;
  height: 600px;
  border-radius: 50%;
  background: radial-gradient(circle, rgba(59, 130, 246, 0.08) 0%, transparent 70%);
  top: -200px;
  right: -200px;
  pointer-events: none;
}
.hero::after {
  content: '';
  position: absolute;
  width: 400px;
  height: 400px;
  border-radius: 50%;
  background: radial-gradient(circle, rgba(5, 150, 105, 0.06) 0%, transparent 70%);
  bottom: -100px;
  left: -100px;
  pointer-events: none;
}

.hero-grid {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 4rem;
  align-items: center;
  width: 100%;
  position: relative;
  z-index: 1;
}

.hero-content {
  max-width: 560px;
}

.hero-badge {
  display: inline-flex;
  align-items: center;
  gap: 0.5rem;
  padding: 0.375rem 0.875rem;
  background: rgba(255, 255, 255, 0.1);
  border: 1px solid rgba(255, 255, 255, 0.15);
  border-radius: 100px;
  font-size: 0.8125rem;
  font-weight: 500;
  color: var(--text-on-dark);
  margin-bottom: 1.5rem;
}

.hero-badge-dot {
  width: 6px;
  height: 6px;
  border-radius: 50%;
  background: var(--color-accent);
  animation: pulse-dot 2s ease-in-out infinite;
}

@keyframes pulse-dot {
  0%, 100% { opacity: 1; }
  50% { opacity: 0.4; }
}

.hero h1 {
  font-size: clamp(2.25rem, 5vw, 3.5rem);
  font-weight: 800;
  line-height: 1.15;
  margin-bottom: 1rem;
  letter-spacing: -0.02em;
}

.hero h1 .highlight {
  color: var(--color-accent);
}

.hero-sub {
  font-size: clamp(1.125rem, 2vw, 1.375rem);
  color: rgba(241, 245, 249, 0.85);
  margin-bottom: 1.5rem;
  line-height: 1.5;
  max-width: 480px;
}

.hero-desc {
  font-size: 1rem;
  color: rgba(241, 245, 249, 0.65);
  margin-bottom: 2rem;
  line-height: 1.7;
  max-width: 440px;
}

.hero-actions {
  display: flex;
  flex-wrap: wrap;
  gap: 0.75rem;
  margin-bottom: 2.5rem;
}

.hero-platform-hint {
  display: flex;
  align-items: center;
  gap: 0.5rem;
  font-size: 0.8125rem;
  color: rgba(241, 245, 249, 0.55);
}
.hero-platform-hint .detected-badge {
  display: inline-flex;
  align-items: center;
  gap: 0.25rem;
  padding: 0.25rem 0.625rem;
  background: rgba(255, 255, 255, 0.08);
  border-radius: 6px;
  font-weight: 500;
  color: rgba(241, 245, 249, 0.75);
}

/* Hero mockup */
.hero-mockup {
  display: flex;
  justify-content: center;
  align-items: center;
}

.hero-mockup-placeholder {
  width: 320px;
  height: 640px;
  background: #000;
  border: 1px solid rgba(255, 255, 255, 0.1);
  border-radius: 32px;
  display: flex;
  flex-direction: column;
  align-items: center;
  justify-content: center;
  position: relative;
  overflow: hidden;
}

.mockup-screen {
  width: calc(100% - 12px);
  height: calc(100% - 12px);
  border-radius: 28px;
  overflow: hidden;
  background: #fff;
  display: flex;
}
.mockup-screen svg {
  opacity: 0.3;
}

.mockup-img {
  width: 100%;
  height: 100%;
  object-fit: cover;
  border-radius: 16px;
  display: block;
}

.mockup-notch {
  width: 100px;
  height: 24px;
  background: rgba(0, 0, 0, 0.3);
  border-radius: 0 0 16px 16px;
  position: absolute;
  top: 0;
}

/* ── Features ── */
.features-grid {
  display: grid;
  grid-template-columns: repeat(2, 1fr);
  gap: 1.5rem;
}

.feature-card {
  background: var(--surface-card);
  border: 1px solid var(--border);
  border-radius: 16px;
  padding: 2rem;
  transition: all var(--duration-normal) var(--ease-out);
}

.feature-card:hover {
  box-shadow: var(--shadow-md);
  border-color: rgba(59, 130, 246, 0.2);
  transform: translateY(-2px);
}

.feature-icon {
  width: 48px;
  height: 48px;
  border-radius: 12px;
  display: flex;
  align-items: center;
  justify-content: center;
  margin-bottom: 1.25rem;
  color: #FFFFFF;
  font-size: 1.25rem;
  font-weight: 700;
}

.feature-icon.read { background: #3B82F6; }
.feature-icon.listen { background: #8B5CF6; }
.feature-icon.speak { background: #059669; }
.feature-icon.spell { background: #F59E0B; }

.feature-card h3 {
  font-size: 1.125rem;
  font-weight: 700;
  margin-bottom: 0.5rem;
  color: var(--text-primary);
}

.feature-card p {
  font-size: 0.9375rem;
  color: var(--text-secondary);
  line-height: 1.6;
}

/* ── How It Works ── */
.steps-grid {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: 2rem;
  counter-reset: step;
}

.step-card {
  text-align: center;
  padding: 2.5rem 1.5rem;
  position: relative;
}

.step-number {
  width: 56px;
  height: 56px;
  border-radius: 50%;
  background: var(--color-primary);
  color: #FFFFFF;
  font-size: 1.375rem;
  font-weight: 700;
  display: flex;
  align-items: center;
  justify-content: center;
  margin: 0 auto 1.5rem;
  position: relative;
}

.step-card h3 {
  font-size: 1.125rem;
  font-weight: 700;
  margin-bottom: 0.5rem;
  color: var(--text-primary);
}

.step-card p {
  font-size: 0.9375rem;
  color: var(--text-secondary);
  line-height: 1.6;
  max-width: 300px;
  margin: 0 auto;
}

/* Connector line between steps */
.step-card:not(:last-child)::after {
  content: '';
  position: absolute;
  top: 3rem;
  right: -1.25rem;
  width: 2.5rem;
  height: 2px;
  background: var(--border);
  display: none;
}
@media (min-width: 768px) {
  .step-card:not(:last-child)::after {
    display: block;
  }
}

/* ── Download / Platforms ── */
.download-intro {
  text-align: center;
  margin-bottom: 3rem;
}

.download-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(180px, 1fr));
  gap: 1rem;
  max-width: 800px;
  margin: 0 auto 3rem;
}

.download-card {
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: 0.75rem;
  padding: 1.75rem 1rem;
  background: var(--surface-card);
  border: 1px solid var(--border);
  border-radius: 14px;
  text-align: center;
  transition: all var(--duration-normal) var(--ease-out);
  text-decoration: none;
  color: var(--text-primary);
  cursor: pointer;
}

.download-card:hover {
  box-shadow: var(--shadow-md);
  border-color: var(--color-primary-light);
  transform: translateY(-2px);
  color: var(--text-primary);
}

.download-card.active {
  border-color: var(--color-accent);
  box-shadow: 0 0 0 2px rgba(5, 150, 105, 0.15);
}

.download-card-icon {
  width: 40px;
  height: 40px;
  display: flex;
  align-items: center;
  justify-content: center;
  color: var(--color-primary);
}

.download-card .platform-name {
  font-size: 0.9375rem;
  font-weight: 600;
}

.download-card .platform-hint {
  font-size: 0.75rem;
  color: var(--text-muted);
}

.download-card .os-badge {
  font-size: 0.6875rem;
  padding: 0.125rem 0.5rem;
  background: var(--surface-muted);
  border-radius: 4px;
  color: var(--text-muted);
  font-weight: 500;
}

.download-note {
  text-align: center;
  font-size: 0.875rem;
  color: var(--text-muted);
  margin-top: 1.5rem;
}

/* ── Footer ── */
.footer {
  background: var(--color-primary-dark);
  color: var(--text-on-dark);
  padding: 3rem 0;
}

.footer-inner {
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: 1.5rem;
  text-align: center;
}

.footer-brand {
  display: flex;
  align-items: center;
  gap: 0.5rem;
  font-size: 1rem;
  font-weight: 600;
}

.footer-brand svg {
  width: 24px;
  height: 24px;
}

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

.footer-links a {
  color: rgba(241, 245, 249, 0.6);
  font-size: 0.875rem;
  transition: color var(--duration-fast) var(--ease-out);
}
.footer-links a:hover {
  color: #FFFFFF;
}

.footer-copyright {
  font-size: 0.8125rem;
  color: rgba(241, 245, 249, 0.4);
}

.footer-icp {
  font-size: 0.8125rem;
}
.footer-icp a {
  color: rgba(241, 245, 249, 0.4);
  text-decoration: none;
  transition: color var(--duration-fast) var(--ease-out);
}
.footer-icp a:hover {
  color: rgba(241, 245, 249, 0.7);
  text-decoration: underline;
}

/* ── Modal ── */
.modal-overlay {
  display: none;
  position: fixed;
  inset: 0;
  z-index: 200;
  background: rgba(15, 23, 42, 0.6);
  backdrop-filter: blur(4px);
  -webkit-backdrop-filter: blur(4px);
  padding: 2rem;
  align-items: center;
  justify-content: center;
}

.modal-overlay.open {
  display: flex;
}

.modal {
  background: var(--surface);
  border-radius: 16px;
  max-width: 720px;
  width: 100%;
  max-height: 80vh;
  overflow-y: auto;
  box-shadow: var(--shadow-lg);
  position: relative;
}

.modal-header {
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding: 1.25rem 1.5rem;
  border-bottom: 1px solid var(--border);
  position: sticky;
  top: 0;
  background: var(--surface);
  border-radius: 16px 16px 0 0;
}

.modal-header h2 {
  font-size: 1.125rem;
  font-weight: 700;
}

.modal-close {
  width: 36px;
  height: 36px;
  border-radius: 8px;
  border: none;
  background: var(--surface-muted);
  cursor: pointer;
  display: flex;
  align-items: center;
  justify-content: center;
  color: var(--text-secondary);
  transition: background var(--duration-fast) var(--ease-out);
}
.modal-close:hover {
  background: var(--border);
}

.modal-body {
  padding: 1.5rem;
  font-size: 0.9375rem;
  line-height: 1.7;
  color: var(--text-secondary);
}

.modal-body h1,
.modal-body h2,
.modal-body h3 {
  color: var(--text-primary);
  margin-top: 1.5em;
  margin-bottom: 0.5em;
}
.modal-body h1 { font-size: 1.25rem; }
.modal-body h2 { font-size: 1.125rem; }
.modal-body h3 { font-size: 1rem; }

.modal-body p {
  margin-bottom: 1em;
}

.modal-body ul,
.modal-body ol {
  margin-bottom: 1em;
  padding-left: 1.5rem;
}

.modal-body li {
  margin-bottom: 0.25em;
}

.modal-body strong {
  color: var(--text-primary);
}

.modal-body hr {
  border: none;
  border-top: 1px solid var(--border);
  margin: 1.5em 0;
}

.modal-body a {
  color: var(--color-primary-light);
  text-decoration: underline;
}
.modal-body a:hover {
  color: var(--color-primary);
}

/* ── Scroll Animation ── */
.reveal {
  opacity: 0;
  transform: translateY(24px);
  transition: opacity 0.6s var(--ease-out), transform 0.6s var(--ease-out);
}

.reveal.visible {
  opacity: 1;
  transform: translateY(0);
}

/* ── Responsive ── */

/* Tablet */
@media (max-width: 900px) {
  .hero-grid {
    grid-template-columns: 1fr;
    gap: 3rem;
    text-align: center;
  }
  .hero-content {
    max-width: 100%;
  }
  .hero-desc,
  .hero-sub {
    max-width: 100%;
  }
  .hero-actions {
    justify-content: center;
  }
  .hero-platform-hint {
    justify-content: center;
  }
  .hero-mockup {
    display: none;
  }
}

/* Phone */
@media (max-width: 640px) {
  .features-grid {
    grid-template-columns: 1fr;
  }

  .steps-grid {
    grid-template-columns: 1fr;
    gap: 1.5rem;
  }

  .step-card:not(:last-child)::after {
    display: none;
  }

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

  .header-nav .btn span {
    display: none;
  }
}