body {
  font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, 'Helvetica Neue', Arial, 'PingFang SC', 'Hiragino Sans GB', 'Microsoft YaHei', sans-serif;
  margin: 0;
  background: #f7f9fc;
  color: #222;
}

.container {
  max-width: 1200px;
  margin: 0 auto;
  padding: 0 20px;
}

.site-header {
  background: #fff;
  border-bottom: 1px solid #e5eaf3;
  position: sticky;
  top: 0;
  z-index: 10;
}
.header-container {
  display: flex;
  align-items: center;
  justify-content: space-between;
  height: 60px;
}
.logo {
  font-size: 1.3rem;
  font-weight: bold;
  color: #3a6cff;
  letter-spacing: 2px;
  display: flex;
  align-items: center;
}
nav ul {
  list-style: none;
  display: flex;
  gap: 30px;
  margin: 0;
  padding: 0;
}
nav a {
  color: #222;
  text-decoration: none;
  font-weight: 500;
  transition: color 0.2s;
}
nav a:hover {
  color: #6c63ff;
}
.btn-primary {
  background: linear-gradient(90deg, #3a6cff 0%, #6c63ff 100%);
  color: #fff;
  border: none;
  border-radius: 8px;
  padding: 10px 24px;
  font-size: 1rem;
  font-weight: 600;
  cursor: pointer;
  text-decoration: none;
  transition: box-shadow 0.2s, background 0.2s;
  box-shadow: 0 2px 8px rgba(106, 99, 255, 0.08);
}
.btn-primary:hover {
  background: linear-gradient(90deg, #6c63ff 0%, #3a6cff 100%);
}
.btn-secondary {
  background: #fff;
  color: #3a6cff;
  border: 1px solid #3a6cff;
  border-radius: 8px;
  padding: 10px 24px;
  font-size: 1rem;
  font-weight: 600;
  margin-left: 16px;
  cursor: pointer;
  text-decoration: none;
  transition: background 0.2s, color 0.2s;
}
.btn-secondary:hover {
  background: #f0f4ff;
}

.hero {
  background: linear-gradient(120deg, #f0f4ff 0%, #f7f9fc 100%);
  padding: 60px 0 40px 0;
  position: relative;
  overflow: hidden;
}
.hero-content {
  text-align: left;
  position: relative;
  opacity: 0;
  transform: translateY(40px);
  animation: heroFadeIn 1s ease-out 0.2s forwards;
}
@keyframes heroFadeIn {
  to {
    opacity: 1;
    transform: none;
  }
}
.hero h1 {
  font-size: 2.5rem;
  font-weight: 700;
  margin-bottom: 18px;
}
.highlight {
  color: #3a6cff;
}
.hero p {
  font-size: 1.2rem;
  margin-bottom: 28px;
  color: #444;
}
.hero-actions {
  margin-bottom: 32px;
}
.hero-icons {
  position: absolute;
  right: 60px;
  top: 40px;
  display: flex;
  gap: 32px;
}
.icon {
  font-size: 2.5rem;
  opacity: 0.18;
}
.icon.large {
  font-size: 3.5rem;
  opacity: 0.28;
}

.intro-section {
  background: #fff;
  padding: 56px 0 36px 0;
}
.intro-section h2 {
  text-align: center;
  font-size: 2rem;
  margin-bottom: 10px;
}
.intro-section p {
  text-align: center;
  color: #555;
  margin-bottom: 32px;
}
.intro-cards {
  display: flex;
  gap: 24px;
  justify-content: center;
  flex-wrap: wrap;
}
.card {
  background: #f7f9fc;
  border-radius: 14px;
  box-shadow: 0 2px 8px rgba(106, 99, 255, 0.04);
  padding: 28px 22px;
  flex: 1 1 260px;
  min-width: 220px;
  max-width: 320px;
  text-align: center;
}
.card-icon {
  font-size: 2.2rem;
  margin-bottom: 10px;
}

.impact-section {
  background: #f0f4ff;
  padding: 56px 0 36px 0;
}
.impact-section h2 {
  text-align: center;
  font-size: 2rem;
  margin-bottom: 32px;
}
.impact-list {
  display: flex;
  flex-wrap: wrap;
  gap: 24px;
  justify-content: center;
}
.impact-item {
  background: #fff;
  border-radius: 14px;
  box-shadow: 0 2px 8px rgba(106, 99, 255, 0.04);
  padding: 24px 20px;
  flex: 1 1 260px;
  min-width: 220px;
  max-width: 340px;
  display: flex;
  gap: 18px;
  align-items: flex-start;
}
.impact-number {
  background: linear-gradient(90deg, #3a6cff 0%, #6c63ff 100%);
  color: #fff;
  font-size: 1.5rem;
  font-weight: bold;
  border-radius: 50%;
  width: 36px;
  height: 36px;
  display: flex;
  align-items: center;
  justify-content: center;
  margin-right: 8px;
}
.impact-item h3 {
  margin: 0 0 8px 0;
  font-size: 1.1rem;
}
.impact-item ul {
  margin: 0;
  padding-left: 18px;
  color: #555;
  font-size: 0.98rem;
}

.projects-section {
  background: #fff;
  padding: 56px 0 36px 0;
}
.projects-section h2 {
  text-align: center;
  font-size: 2rem;
  margin-bottom: 32px;
}
.projects-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(260px, 1fr));
  gap: 24px;
}
.project-card {
  background: #f7f9fc;
  border-radius: 14px;
  box-shadow: 0 2px 8px rgba(106, 99, 255, 0.04);
  padding: 24px 18px 18px 18px;
  display: flex;
  flex-direction: column;
  align-items: flex-start;
  transition: transform 0.2s, box-shadow 0.2s;
  position: relative;
  overflow: hidden;
}
.project-card:hover {
  transform: translateY(-6px) scale(1.03);
  box-shadow: 0 8px 32px rgba(106, 99, 255, 0.13);
  z-index: 2;
}
.project-card .card-overlay {
  display: none;
  position: absolute;
  inset: 0;
  background: rgba(106,99,255,0.08);
  color: #222;
  align-items: center;
  justify-content: center;
  font-size: 1rem;
  padding: 24px;
  z-index: 3;
}
.project-card:hover .card-overlay {
  display: flex;
}
.project-title {
  font-weight: bold;
  font-size: 1.1rem;
  margin-bottom: 10px;
  display: flex;
  align-items: center;
  gap: 8px;
}
.tag {
  background: #e5eaf3;
  color: #3a6cff;
  border-radius: 6px;
  font-size: 0.85rem;
  padding: 2px 8px;
}
.project-img {
  font-size: 2.2rem;
  margin-bottom: 10px;
}
.btn-link {
  color: #3a6cff;
  text-decoration: underline;
  font-size: 0.98rem;
  margin-top: 8px;
  align-self: flex-end;
}
.btn-link:hover {
  color: #6c63ff;
}

.participate-section {
  background: #f0f4ff;
  padding: 56px 0 36px 0;
}
.participate-section h2 {
  text-align: center;
  font-size: 2rem;
  margin-bottom: 32px;
}
.participate-steps {
  display: flex;
  gap: 24px;
  justify-content: center;
  flex-wrap: wrap;
  margin-bottom: 24px;
}
.step-card {
  background: #fff;
  border-radius: 14px;
  box-shadow: 0 2px 8px rgba(106, 99, 255, 0.04);
  padding: 28px 22px;
  flex: 1 1 260px;
  min-width: 220px;
  max-width: 320px;
  text-align: center;
}
.step-icon {
  font-size: 2.2rem;
  margin-bottom: 10px;
}

.faq-section {
  background: #fff;
  padding: 56px 0 36px 0;
}
.faq-section h2 {
  text-align: center;
  font-size: 2rem;
  margin-bottom: 32px;
}
.faq-list {
  max-width: 700px;
  margin: 0 auto;
}
.faq-item {
  border-bottom: 1px solid #e5eaf3;
}
.faq-question {
  width: 100%;
  background: none;
  border: none;
  outline: none;
  text-align: left;
  font-size: 1.08rem;
  font-weight: 500;
  padding: 18px 0;
  cursor: pointer;
  color: #3a6cff;
  transition: color 0.2s;
}
.faq-question:hover {
  color: #6c63ff;
}
.faq-answer {
  max-height: 0;
  overflow: hidden;
  transition: max-height 0.35s cubic-bezier(.4,0,.2,1), padding 0.35s, opacity 0.35s;
  opacity: 0;
  padding-bottom: 0;
}
.faq-item.active .faq-answer {
  max-height: 200px;
  opacity: 1;
  padding-bottom: 16px;
}

.site-footer {
  background: #181c2a;
  color: #fff;
  padding: 40px 0 0 0;
  margin-top: 40px;
}
.footer-container {
  display: flex;
  flex-wrap: wrap;
  gap: 32px;
  justify-content: space-between;
  max-width: 1200px;
  margin: 0 auto;
  padding: 0 20px;
}
.footer-col {
  flex: 1 1 180px;
  min-width: 160px;
  margin-bottom: 24px;
}
.footer-col h4 {
  font-size: 1.05rem;
  margin-bottom: 12px;
  color: #6c63ff;
}
.footer-col ul {
  list-style: none;
  padding: 0;
  margin: 0;
}
.footer-col ul li {
  margin-bottom: 8px;
}
.footer-col a {
  color: #e5eaf3;
  text-decoration: none;
  transition: color 0.2s;
}
.footer-col a:hover {
  color: #3a6cff;
}
.footer-bottom {
  text-align: center;
  color: #aaa;
  font-size: 0.95rem;
  padding: 18px 0 10px 0;
  border-top: 1px solid #23263a;
  margin-top: 10px;
}

@media (max-width: 900px) {
  .header-container, .footer-container {
    flex-direction: column;
    align-items: flex-start;
    gap: 18px;
    height: auto;
  }
  .hero-icons {
    position: static;
    margin-top: 24px;
    justify-content: flex-end;
  }
  .intro-cards, .impact-list, .participate-steps {
    flex-direction: column;
    align-items: stretch;
  }
  .projects-grid {
    grid-template-columns: 1fr;
  }
}

html {
  scroll-behavior: smooth;
}

/* Modal styles */
.modal-overlay {
  position: fixed;
  inset: 0;
  background: rgba(24,28,42,0.55);
  display: flex;
  align-items: center;
  justify-content: center;
  z-index: 1000;
  animation: modalFadeIn 0.25s;
}
@keyframes modalFadeIn {
  from { opacity: 0; }
  to { opacity: 1; }
}
.modal-box {
  background: #fff;
  border-radius: 14px;
  box-shadow: 0 8px 32px rgba(106, 99, 255, 0.18);
  max-width: 420px;
  width: 90vw;
  padding: 32px 28px 24px 28px;
  position: relative;
  animation: modalPopIn 0.3s cubic-bezier(.23,1.01,.32,1) forwards;
}
@keyframes modalPopIn {
  from { transform: scale(0.92); opacity: 0; }
  to { transform: scale(1); opacity: 1; }
}
.modal-close {
  position: absolute;
  top: 12px;
  right: 16px;
  background: none;
  border: none;
  font-size: 1.5rem;
  color: #6c63ff;
  cursor: pointer;
}

/* Back to top button */
#backToTopBtn {
  position: fixed;
  right: 32px;
  bottom: 40px;
  z-index: 1200;
  background: linear-gradient(90deg, #3a6cff 0%, #6c63ff 100%);
  color: #fff;
  border: none;
  border-radius: 50%;
  width: 48px;
  height: 48px;
  font-size: 1.6rem;
  box-shadow: 0 2px 8px rgba(106, 99, 255, 0.18);
  cursor: pointer;
  display: none;
  align-items: center;
  justify-content: center;
  transition: background 0.2s, opacity 0.2s;
  opacity: 0.85;
}
#backToTopBtn:hover {
  background: linear-gradient(90deg, #6c63ff 0%, #3a6cff 100%);
  opacity: 1;
}