/* Root Variables & Reset */
:root {
  --color-bg: #ffffff;
  --color-text-main: #333333;
  --color-text-light: #666666;
  --color-text-lighter: #999999;
  --color-accent: #0066cc;
  --color-accent-hover: #0052a3;
  --color-accent-secondary: #2e7d32;
  --color-border: #e5e5e5;
  --color-card-bg: #f9f9f9;
  --color-section-alt: #f5f7fa;
  
  --spacing-unit: 1rem;
  --max-width: 960px;
  --header-height: 60px;
  --border-radius: 10px;
}

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

html {
  scroll-behavior: smooth;
}

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

a {
  text-decoration: none;
  color: inherit;
  transition: color 0.2s ease;
}

ul {
  list-style: none;
}

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

/* Typography */
h1, h2, h3, h4 {
  line-height: 1.3;
  margin-bottom: 1rem;
  font-weight: 700;
  color: var(--color-text-main);
}

h1 { font-size: 2rem; }
h2 { font-size: 1.5rem; }
h3 { font-size: 1.25rem; }
h4 { font-size: 1.1rem; }
p { margin-bottom: 1rem; color: var(--color-text-light); }

/* Layout Utilities */
.container {
  width: 100%;
  max-width: var(--max-width);
  margin: 0 auto;
  padding: 0 1.5rem;
}

.section {
  padding: 4rem 0;
}

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

/* Buttons */
.btn {
  display: inline-block;
  padding: 0.875rem 1.75rem;
  background-color: var(--color-accent);
  color: white;
  border-radius: var(--border-radius);
  font-weight: 600;
  text-align: center;
  border: none;
  cursor: pointer;
  transition: background-color 0.2s ease, box-shadow 0.2s ease;
}

.btn:hover {
  background-color: var(--color-accent-hover);
  box-shadow: 0 2px 8px rgba(0, 102, 204, 0.25);
}

.btn-large {
  font-size: 1.1rem;
  padding: 1rem 2rem;
}

.text-center { text-align: center; }
.mb-1 { margin-bottom: 1rem; }
.mb-2 { margin-bottom: 2rem; }

/* Header & Nav */
header {
  height: var(--header-height);
  background: white;
  border-bottom: 1px solid var(--color-border);
  position: sticky;
  top: 0;
  z-index: 100;
  display: flex;
  align-items: center;
}

.nav-container {
  display: flex;
  justify-content: space-between;
  align-items: center;
  width: 100%;
}

.logo {
  font-weight: 700;
  font-size: 1.25rem;
  color: var(--color-accent);
}

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

.nav-link {
  font-size: 0.95rem;
  color: var(--color-text-light);
  padding: 0.5rem 0;
  border-bottom: 2px solid transparent;
  transition: color 0.2s, border-color 0.2s;
}

.nav-link:hover {
  color: var(--color-accent);
}

.nav-link.active {
  color: var(--color-accent);
  border-bottom-color: var(--color-accent);
  font-weight: 600;
}

/* Hamburger Menu (Mobile) */
.hamburger {
  display: none;
  flex-direction: column;
  gap: 5px;
  cursor: pointer;
  padding: 0.5rem;
}

.bar {
  width: 24px;
  height: 2px;
  background-color: var(--color-text-main);
  transition: 0.3s;
  border-radius: 2px;
}

/* Mobile Styles */
@media (max-width: 768px) {
  .hamburger {
    display: flex;
  }

  .nav-menu {
    position: fixed;
    top: var(--header-height);
    left: -100%;
    width: 100%;
    height: calc(100vh - var(--header-height));
    background: white;
    flex-direction: column;
    align-items: center;
    padding-top: 2rem;
    gap: 0;
    transition: 0.3s;
    border-top: 1px solid var(--color-border);
  }

  .nav-menu li {
    width: 100%;
    text-align: center;
  }

  .nav-menu .nav-link {
    display: block;
    padding: 1rem;
    border-bottom: 1px solid var(--color-border);
  }

  .nav-menu .nav-link.active {
    background-color: var(--color-section-alt);
    border-bottom: 1px solid var(--color-border);
  }

  .nav-menu.active {
    left: 0;
  }

  .section {
    padding: 3rem 0;
  }

  h1 {
    font-size: 1.75rem;
  }
}

/* Hero */
.hero {
  padding: 4rem 1rem;
  text-align: center;
  background-color: #f0f7ff;
}

.hero h1 {
  margin-bottom: 1rem;
}

.hero-subtitle {
  font-size: 1.1rem;
  color: var(--color-text-light);
  margin-bottom: 0.75rem;
}

.hero-note {
  font-size: 0.9rem;
  color: var(--color-text-lighter);
  margin-bottom: 1.5rem;
  max-width: 500px;
  margin-left: auto;
  margin-right: auto;
}

.hero-hint {
  font-size: 0.85rem;
  color: var(--color-text-lighter);
  margin-top: 1rem;
  margin-bottom: 0;
}

/* Cards (Grid) */
.grid-3 {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(280px, 1fr));
  gap: 1.5rem;
}

.card {
  background: var(--color-card-bg);
  padding: 2rem;
  border-radius: var(--border-radius);
  border: 1px solid var(--color-border);
  transition: transform 0.2s, box-shadow 0.2s;
}

.card:hover {
  transform: translateY(-3px);
  box-shadow: 0 4px 12px rgba(0, 0, 0, 0.06);
}

.card-icon {
  width: 48px;
  height: 48px;
  display: flex;
  align-items: center;
  justify-content: center;
  font-size: 1.5rem;
  font-weight: bold;
  margin-bottom: 1rem;
  color: white;
  background-color: var(--color-accent-secondary);
  border-radius: 50%;
}

/* 30秒理解模块 */
.quick-understand {
  max-width: 700px;
  margin: 0 auto;
  text-align: center;
}

.quick-understand h2 {
  margin-bottom: 1.5rem;
}

.quick-understand-desc {
  font-size: 1rem;
  line-height: 1.8;
  margin-bottom: 2rem;
}

.quick-list {
  display: inline-block;
  text-align: left;
}

.quick-list li {
  font-size: 1rem;
  color: var(--color-text-main);
  padding: 0.5rem 0;
  display: flex;
  align-items: center;
  gap: 0.75rem;
}

.check-icon {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  width: 24px;
  height: 24px;
  background-color: var(--color-accent-secondary);
  color: white;
  border-radius: 50%;
  font-size: 0.85rem;
  flex-shrink: 0;
}

/* QR Notice Box */
.qr-notice {
  display: inline-block;
  margin-top: 1.5rem;
  padding: 1rem 1.5rem;
  background-color: white;
  border: 1px solid var(--color-border);
  border-radius: var(--border-radius);
  font-size: 0.95rem;
  color: var(--color-text-light);
  line-height: 1.8;
  max-width: 600px;
}

/* Feature List */
.feature-list {
  display: grid;
  gap: 1.5rem;
  margin-top: 1.5rem;
}

.feature-item {
  background: white;
  padding: 1.5rem;
  border-radius: var(--border-radius);
  border: 1px solid var(--color-border);
}

.feature-item h4 {
  color: var(--color-accent);
  margin-bottom: 0.5rem;
}

.feature-item p {
  margin-bottom: 0;
  font-size: 0.95rem;
}

/* Content Blocks */
.content-block {
  margin-bottom: 2.5rem;
}

.content-block h3 {
  margin-bottom: 1rem;
  padding-bottom: 0.5rem;
  border-bottom: 2px solid var(--color-accent);
  display: inline-block;
}

.content-list {
  list-style: disc;
  margin-left: 1.5rem;
  color: var(--color-text-light);
}

.content-list li {
  margin-bottom: 0.5rem;
}

/* Accordion (FAQ) */
.accordion-item {
  border-bottom: 1px solid var(--color-border);
}

.accordion-header {
  width: 100%;
  padding: 1.25rem 0;
  background: none;
  border: none;
  text-align: left;
  font-size: 1.05rem;
  font-weight: 600;
  cursor: pointer;
  display: flex;
  justify-content: space-between;
  align-items: center;
  color: var(--color-text-main);
  transition: color 0.2s;
}

.accordion-header:hover {
  color: var(--color-accent);
}

.accordion-content {
  max-height: 0;
  overflow: hidden;
  transition: max-height 0.3s ease-out;
  padding-right: 1rem;
}

.accordion-content p {
  padding-bottom: 1.25rem;
}

.icon-plus {
  font-size: 1.25rem;
  transition: transform 0.3s;
  color: var(--color-accent);
}

.accordion-item.active .icon-plus {
  transform: rotate(45deg);
}

/* Trust Section */
.trust-section {
  background-color: var(--color-card-bg);
  border-left: 4px solid var(--color-accent-secondary);
  padding: 1.5rem;
  border-radius: 0 var(--border-radius) var(--border-radius) 0;
}

/* Note Text */
.note-text {
  font-size: 0.9rem;
  color: var(--color-text-lighter);
  font-style: italic;
  margin-top: 1rem;
}

/* Summary Block */
.summary-block {
  max-width: 700px;
  margin: 0 auto;
}

.summary-block p {
  font-size: 1.1rem;
  line-height: 1.9;
}

.trust-section h4 {
  margin-bottom: 1rem;
}

.source-list {
  list-style: disc;
  margin-left: 1.5rem;
  color: var(--color-text-light);
}

.source-list li {
  margin-bottom: 0.5rem;
}

/* Footer */
footer {
  background: var(--color-section-alt);
  padding: 2rem 0;
  margin-top: 4rem;
  text-align: center;
  font-size: 0.9rem;
  border-top: 1px solid var(--color-border);
}

footer p {
  color: var(--color-text-lighter);
  margin-bottom: 0;
}

/* About Page Styles */
.feedback-box {
  background: var(--color-card-bg);
  padding: 1.5rem;
  border-radius: var(--border-radius);
  border-left: 4px solid var(--color-accent);
}

.feedback-box p {
  margin-bottom: 0.75rem;
}

.feedback-box p:last-child {
  margin-bottom: 0;
}