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

:root {
  --primary: #607CD2;
  --primary-dark: #4a63b5;
  --primary-light: #eef1fa;
  --bg: #ffffff;
  --bg-warm: #f8f6f3;
  --bg-dark: #1a1a2e;
  --text: #1a1a2e;
  --text-secondary: #666;
  --text-light: #888;
  --border: #e8e8e8;
  --card-shadow: 0 2px 12px rgba(0,0,0,0.06);
  --card-radius: 12px;
  --max-width: 1200px;
}

html {
  scroll-behavior: smooth;
}

body {
  font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", "Noto Sans SC", "PingFang SC", "Microsoft YaHei", sans-serif;
  font-size: 16px;
  color: var(--text);
  background: var(--bg);
  line-height: 1.6;
  -webkit-font-smoothing: antialiased;
}

a {
  color: var(--primary);
  text-decoration: none;
  transition: color 0.2s;
}

a:hover {
  color: var(--primary-dark);
}

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

.container {
  max-width: var(--max-width);
  margin: 0 auto;
  padding: 0 24px;
}

/* === Navigation === */
nav {
  position: fixed;
  top: 0;
  left: 0;
  right: 0;
  z-index: 100;
  background: rgba(255,255,255,0.9);
  backdrop-filter: blur(12px);
  -webkit-backdrop-filter: blur(12px);
  border-bottom: 1px solid transparent;
  transition: border-color 0.3s, box-shadow 0.3s;
}

nav.scrolled {
  border-bottom-color: var(--border);
  box-shadow: 0 1px 6px rgba(0,0,0,0.04);
}

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

.nav-brand {
  display: flex;
  align-items: center;
  gap: 10px;
  font-size: 18px;
  font-weight: 700;
  color: var(--text);
}

.nav-brand img {
  width: 32px;
  height: 32px;
  border-radius: 6px;
}

.nav-install {
  padding: 8px 20px;
  background: var(--primary);
  color: #fff;
  border-radius: 8px;
  font-size: 14px;
  font-weight: 600;
  transition: background 0.2s;
}

.nav-install:hover {
  background: var(--primary-dark);
  color: #fff;
}

/* === Hero === */
.hero {
  min-height: 100vh;
  display: flex;
  align-items: center;
  padding-top: 64px;
  background: linear-gradient(135deg, #f8f9ff 0%, var(--bg-warm) 100%);
  overflow: hidden;
}

.hero .container {
  display: flex;
  align-items: center;
  gap: 60px;
  padding-top: 40px;
  padding-bottom: 40px;
}

.hero-content {
  flex: 1;
}

.hero-content h1 {
  font-size: 44px;
  font-weight: 800;
  line-height: 1.2;
  margin-bottom: 16px;
  letter-spacing: -0.02em;
}

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

.hero-sub {
  font-size: 18px;
  color: var(--text-secondary);
  margin-bottom: 12px;
  line-height: 1.6;
}

.hero-hint {
  font-size: 14px;
  color: var(--text-light);
  margin-bottom: 32px;
}

.hero-buttons {
  display: flex;
  flex-wrap: wrap;
  gap: 12px;
}

.btn {
  display: inline-flex;
  align-items: center;
  gap: 8px;
  padding: 14px 28px;
  border-radius: 10px;
  font-size: 15px;
  font-weight: 600;
  border: none;
  cursor: pointer;
  transition: all 0.2s;
  text-decoration: none;
}

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

.btn-primary:hover {
  background: var(--primary-dark);
  color: #fff;
  transform: translateY(-1px);
  box-shadow: 0 4px 12px rgba(96,124,210,0.3);
}

.btn-secondary {
  background: #fff;
  color: var(--text);
  border: 1.5px solid var(--border);
}

.btn-secondary:hover {
  border-color: var(--primary);
  color: var(--primary);
  transform: translateY(-1px);
  box-shadow: 0 4px 12px rgba(0,0,0,0.06);
}

.btn-edge {
  background: #107c10;
  color: #fff;
}

.btn-edge:hover {
  background: #0b5e0b;
  color: #fff;
  transform: translateY(-1px);
  box-shadow: 0 4px 12px rgba(16,124,16,0.3);
}

.btn-quark {
  background: #1a7de0;
  color: #fff;
}

.btn-quark:hover {
  background: #1462b0;
  color: #fff;
  transform: translateY(-1px);
  box-shadow: 0 4px 12px rgba(26,125,224,0.3);
}

.hero-image {
  flex: 0 0 320px;
  display: flex;
  align-items: center;
  justify-content: center;
}

/* === Section common === */
.section {
  padding: 100px 0;
}

.section-title {
  text-align: center;
  font-size: 36px;
  font-weight: 700;
  margin-bottom: 12px;
}

.section-desc {
  text-align: center;
  color: var(--text-secondary);
  font-size: 17px;
  max-width: 600px;
  margin: 0 auto 60px;
}

.section-alt {
  background: var(--bg-warm);
}

/* === Hobby === */
.hobby-grid {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 40px;
  max-width: 700px;
  margin: 0 auto;
}

.hobby-item {
  text-align: center;
  background: #fff;
  border-radius: var(--card-radius);
  padding: 32px 24px;
  border: 1px solid var(--border);
  transition: transform 0.2s, box-shadow 0.2s;
}

.hobby-item:hover {
  transform: translateY(-4px);
  box-shadow: var(--card-shadow);
}

.hobby-item img {
  border-radius: 16px;
  margin-bottom: 16px;
}

.hobby-item h3 {
  font-size: 20px;
  font-weight: 700;
  margin-bottom: 8px;
}

.hobby-item p {
  font-size: 14px;
  color: var(--text-secondary);
  line-height: 1.6;
}

/* === Features === */
.features-grid {
  display: grid;
  grid-template-columns: repeat(4, 1fr);
  gap: 20px;
}

.feature-card {
  background: #fff;
  border: 1px solid var(--border);
  border-radius: var(--card-radius);
  padding: 28px 24px;
  transition: transform 0.2s, box-shadow 0.2s, border-color 0.2s;
}

.feature-card:hover {
  transform: translateY(-4px);
  box-shadow: var(--card-shadow);
  border-color: var(--primary-light);
}

.feature-icon {
  font-size: 28px;
  margin-bottom: 12px;
  display: block;
}

.feature-card h3 {
  font-size: 17px;
  font-weight: 700;
  margin-bottom: 8px;
}

.feature-card p {
  font-size: 14px;
  color: var(--text-secondary);
  line-height: 1.5;
}

/* === Screenshots === */
.screenshots-grid {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 32px;
  align-items: start;
}

.screenshot-item {
  text-align: center;
  display: flex;
  flex-direction: column;
  align-items: center;
}

.screenshot-item img {
  max-width: 100%;
  max-height: 75vh;
  width: auto;
  height: auto;
  border-radius: 12px;
  box-shadow: 0 4px 20px rgba(0,0,0,0.08);
  border: 1px solid var(--border);
}

.screenshot-item p {
  margin-top: 12px;
  font-size: 14px;
  color: var(--text-secondary);
}

/* === Privacy === */
.privacy-grid {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: 32px;
  margin-bottom: 40px;
}

.privacy-item {
  text-align: center;
  padding: 32px 24px;
  background: #fff;
  border-radius: var(--card-radius);
  border: 1px solid var(--border);
}

.privacy-icon {
  font-size: 40px;
  margin-bottom: 16px;
  display: block;
}

.privacy-item h3 {
  font-size: 18px;
  font-weight: 700;
  margin-bottom: 8px;
}

.privacy-item p {
  font-size: 14px;
  color: var(--text-secondary);
}

.privacy-link {
  text-align: center;
}

.privacy-link a {
  display: inline-flex;
  align-items: center;
  gap: 4px;
  font-size: 15px;
  font-weight: 600;
}

/* === FAQ === */
.faq-list {
  max-width: 720px;
  margin: 0 auto;
}

.faq-item {
  border: 1px solid var(--border);
  border-radius: var(--card-radius);
  margin-bottom: 12px;
  overflow: hidden;
}

.faq-question {
  width: 100%;
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding: 18px 24px;
  background: none;
  border: none;
  cursor: pointer;
  font-size: 16px;
  font-weight: 600;
  color: var(--text);
  text-align: left;
  gap: 12px;
  transition: background 0.2s;
}

.faq-question:hover {
  background: #fafafa;
}

.faq-question .faq-arrow {
  flex-shrink: 0;
  transition: transform 0.3s;
  color: var(--text-light);
}

.faq-item.open .faq-question .faq-arrow {
  transform: rotate(180deg);
}

.faq-answer {
  max-height: 0;
  overflow: hidden;
  transition: max-height 0.3s ease;
}

.faq-item.open .faq-answer {
  max-height: 300px;
}

.faq-answer-inner {
  padding: 0 24px 18px;
  font-size: 15px;
  color: var(--text-secondary);
  line-height: 1.7;
}

.faq-answer-inner a {
  font-weight: 600;
}

/* === Footer === */
footer {
  background: var(--bg-dark);
  color: #999;
  padding: 48px 0;
  font-size: 14px;
}

footer .container {
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: 16px;
  text-align: center;
}

.footer-links {
  display: flex;
  gap: 24px;
  flex-wrap: wrap;
  justify-content: center;
}

.footer-links a {
  color: #bbb;
  font-size: 14px;
}

.footer-links a:hover {
  color: #fff;
}

footer .copyright {
  color: #666;
  font-size: 13px;
}

/* === Responsive === */
@media (max-width: 1024px) {
  .features-grid {
    grid-template-columns: repeat(3, 1fr);
  }

  .hero-content h1 {
    font-size: 36px;
  }
}

@media (max-width: 768px) {
  .hero .container {
    flex-direction: column;
    text-align: center;
    gap: 32px;
  }

  .hero-content h1 {
    font-size: 32px;
  }

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

  .hero-image {
    flex: 0 0 auto;
    max-width: 280px;
    margin: 0 auto;
  }

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

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

  .hobby-grid {
    grid-template-columns: 1fr;
    gap: 24px;
  }

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

  .section {
    padding: 64px 0;
  }

  .section-title {
    font-size: 28px;
  }
}

@media (max-width: 480px) {
  .features-grid {
    grid-template-columns: 1fr;
  }

  .hero-content h1 {
    font-size: 26px;
  }

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

  .btn {
    justify-content: center;
  }

  .container {
    padding: 0 16px;
  }
}

/* === Smooth fade-in animation === */
.fade-in {
  opacity: 0;
  transform: translateY(30px);
  transition: opacity 0.6s ease, transform 0.6s ease;
}

.fade-in.visible {
  opacity: 1;
  transform: translateY(0);
}