@import url('https://fonts.googleapis.com/css2?family=Noto+Sans+SC:wght@300;400;500;600;700;900&display=swap');

:root {
  --brand: #4B8EF2;
  --brand-soft: rgba(75, 142, 242, 0.08);
  --brand-glow: rgba(75, 142, 242, 0.15);
  --bg-main: #ffffff;
  --bg-section: #F7F8FA;
  --bg-card: #ffffff;
  --text: #111111;
  --text-secondary: #555555;
  --text-muted: #999999;
  --border: rgba(0, 0, 0, 0.06);
}

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

html {
  scroll-behavior: smooth;
}

body {
  font-family: 'Noto Sans SC', -apple-system, 'Helvetica Neue', sans-serif;
  background: var(--bg-main);
  color: var(--text);
  min-height: 100vh;
  -webkit-font-smoothing: antialiased;
}

/* ======== 导航 ======== */
.nav {
  position: fixed;
  top: 0;
  left: 0;
  right: 0;
  z-index: 100;
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding: 0 3rem;
  height: 64px;
  background: rgba(255, 255, 255, 0.85);
  backdrop-filter: blur(20px);
  -webkit-backdrop-filter: blur(20px);
  border-bottom: 1px solid var(--border);
  transition: background 0.3s;
}

.nav-logo {
  display: flex;
  align-items: center;
  gap: 0.5rem;
  text-decoration: none;
  color: var(--text);
}

.nav-logo-img {
  width: 28px;
  height: 28px;
  border-radius: 7px;
  flex-shrink: 0;
  object-fit: contain;
}

.nav-logo span {
  font-size: 1rem;
  font-weight: 700;
  letter-spacing: 0.02em;
}

.nav-links {
  display: flex;
  align-items: center;
  gap: 2rem;
}

.nav-links a {
  color: var(--text-secondary);
  text-decoration: none;
  font-size: 0.85rem;
  font-weight: 500;
  transition: color 0.2s;
  position: relative;
}

.nav-links a:hover,
.nav-links a.active {
  color: var(--brand);
}

.nav-links a.active::after {
  content: '';
  position: absolute;
  bottom: -4px;
  left: 0;
  right: 0;
  height: 2px;
  background: var(--brand);
  border-radius: 1px;
}

@media (max-width: 768px) {
  .nav { padding: 0 1.5rem; }
  .nav-links { gap: 1rem; }
  .nav-links a { font-size: 0.78rem; }
}

/* ======== Hero 全屏首屏 ======== */
.hero {
  display: flex;
  flex-direction: column;
  align-items: center;
  justify-content: center;
  min-height: 100vh;
  padding: 64px 2rem 2rem;
  text-align: center;
  position: relative;
  background: var(--bg-main);
}

.hero-badge {
  display: inline-flex;
  align-items: center;
  gap: 0.5rem;
  padding: 0.4rem 1rem;
  background: var(--brand-soft);
  border: 1px solid rgba(75, 142, 242, 0.12);
  border-radius: 100px;
  font-size: 0.8rem;
  color: var(--brand);
  font-weight: 500;
  margin-bottom: 2rem;
}

.hero-badge i {
  font-size: 0.7rem;
}

.hero-title {
  font-size: 4.5rem;
  font-weight: 900;
  line-height: 1.15;
  margin-bottom: 1.5rem;
  letter-spacing: -0.02em;
}

.hero-title .brand-text {
  color: var(--brand);
}

.hero-subtitle {
  font-size: 1.15rem;
  color: var(--text-secondary);
  max-width: 520px;
  margin: 0 auto 2.5rem;
  line-height: 1.7;
  font-weight: 400;
}

.hero-actions {
  display: flex;
  gap: 1rem;
  justify-content: center;
  margin-bottom: 3rem;
  flex-wrap: wrap;
}

.btn-primary {
  display: inline-flex;
  align-items: center;
  gap: 0.5rem;
  background: var(--brand);
  color: #fff;
  padding: 0.9rem 2.2rem;
  border-radius: 100px;
  font-size: 0.95rem;
  font-weight: 600;
  text-decoration: none;
  border: none;
  cursor: pointer;
  transition: transform 0.2s, box-shadow 0.2s;
  box-shadow: 0 4px 20px var(--brand-glow);
}

.btn-primary:hover {
  transform: translateY(-2px);
  box-shadow: 0 8px 30px rgba(75, 142, 242, 0.25);
}

.btn-secondary {
  display: inline-flex;
  align-items: center;
  gap: 0.5rem;
  background: transparent;
  color: var(--text);
  padding: 0.9rem 2.2rem;
  border-radius: 100px;
  font-size: 0.95rem;
  font-weight: 600;
  text-decoration: none;
  border: 1.5px solid var(--border);
  cursor: pointer;
  transition: border-color 0.2s, color 0.2s;
}

.btn-secondary:hover {
  border-color: var(--brand);
  color: var(--brand);
}

.hero-scroll {
  position: absolute;
  bottom: 2.5rem;
  left: 50%;
  transform: translateX(-50%);
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: 0.5rem;
  color: var(--text-muted);
  font-size: 0.72rem;
  letter-spacing: 0.1em;
  text-transform: uppercase;
  animation: float 2s ease-in-out infinite;
}

.hero-scroll i {
  font-size: 0.9rem;
}

@keyframes float {
  0%, 100% { transform: translateX(-50%) translateY(0); }
  50% { transform: translateX(-50%) translateY(6px); }
}

@media (max-width: 768px) {
  .hero-title { font-size: 2.8rem; }
  .hero-subtitle { font-size: 1rem; }
}

/* ======== 全屏分区通用 ======== */
.section {
  padding: 6rem 2rem;
  position: relative;
}

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

.section-inner {
  max-width: 1100px;
  margin: 0 auto;
}

.section-header {
  text-align: center;
  margin-bottom: 3.5rem;
}

.section-label {
  display: inline-block;
  font-size: 0.75rem;
  font-weight: 600;
  color: var(--brand);
  text-transform: uppercase;
  letter-spacing: 0.12em;
  margin-bottom: 0.8rem;
}

.section-title {
  font-size: 2.5rem;
  font-weight: 800;
  line-height: 1.25;
  margin-bottom: 0.8rem;
  letter-spacing: -0.01em;
}

.section-desc {
  font-size: 1rem;
  color: var(--text-secondary);
  max-width: 560px;
  margin: 0 auto;
  line-height: 1.7;
}

@media (max-width: 768px) {
  .section { padding: 4rem 1.5rem; }
  .section-title { font-size: 1.8rem; }
}

/* ======== 翻译演示卡片 ======== */
.demo-wrapper {
  max-width: 680px;
  margin: 0 auto;
}

.translate-demo {
  background: var(--bg-card);
  border-radius: 20px;
  border: 1px solid var(--border);
  overflow: hidden;
  box-shadow: 0 20px 60px rgba(0, 0, 0, 0.06);
}

.translate-tabs {
  display: flex;
  gap: 0;
  border-bottom: 1px solid var(--border);
}

.translate-tabs .tab {
  padding: 0.85rem 1.2rem;
  font-size: 0.82rem;
  color: var(--text-muted);
  cursor: pointer;
  border-bottom: 2px solid transparent;
  transition: all 0.2s;
  white-space: nowrap;
  font-weight: 500;
}

.translate-tabs .tab.active {
  color: var(--brand);
  border-bottom-color: var(--brand);
  font-weight: 600;
}

.translate-tabs .tab:hover:not(.active) {
  color: var(--text-secondary);
}

.translate-lang-bar {
  display: flex;
  align-items: center;
  gap: 0.75rem;
  padding: 0.7rem 1.2rem;
  border-bottom: 1px solid var(--border);
}

.lang-tag {
  font-size: 0.82rem;
  font-weight: 500;
  color: var(--text-secondary);
  padding: 0.25rem 0.65rem;
  border-radius: 6px;
  background: var(--bg-section);
  cursor: pointer;
  transition: all 0.2s;
}

.lang-tag.active {
  color: #fff;
  background: var(--brand);
}

.swap-icon {
  color: var(--text-muted);
  font-size: 0.75rem;
  cursor: pointer;
  transition: color 0.2s;
}

.swap-icon:hover {
  color: var(--brand);
}

.lang-extra {
  display: flex;
  gap: 0.5rem;
  margin-left: auto;
}

.lang-extra span {
  font-size: 0.75rem;
  color: var(--text-muted);
  cursor: pointer;
  padding: 0.2rem 0.45rem;
  border-radius: 4px;
  transition: all 0.15s;
}

.lang-extra span:hover {
  color: var(--text-secondary);
  background: var(--bg-section);
}

.translate-demo-body {
  padding: 1.4rem 1.5rem;
}

.translate-input {
  position: relative;
  margin-bottom: 0.5rem;
}

.translate-input p {
  font-size: 0.9rem;
  color: var(--text);
  line-height: 1.8;
  padding-bottom: 0.5rem;
}

.char-count {
  position: absolute;
  bottom: 0;
  right: 0;
  font-size: 0.7rem;
  color: var(--text-muted);
}

.translate-divider {
  display: flex;
  align-items: center;
  margin: 0.8rem 0;
  gap: 0.75rem;
}

.translate-divider::before,
.translate-divider::after {
  content: '';
  flex: 1;
  height: 1px;
  background: var(--border);
}

.engine-badge {
  font-size: 0.68rem;
  color: var(--brand);
  background: var(--brand-soft);
  padding: 0.2rem 0.6rem;
  border-radius: 10px;
  white-space: nowrap;
  font-weight: 500;
}

.engine-badge i {
  margin-right: 0.2rem;
}

.translate-output p {
  font-size: 0.88rem;
  color: var(--brand);
  line-height: 1.8;
  opacity: 0.85;
}

.translate-demo-footer {
  display: flex;
  gap: 1.2rem;
  padding: 0.75rem 1.5rem;
  border-top: 1px solid var(--border);
  background: var(--bg-section);
  flex-wrap: wrap;
}

.translate-demo-footer span {
  font-size: 0.72rem;
  color: var(--text-muted);
  white-space: nowrap;
}

.translate-demo-footer i {
  margin-right: 0.25rem;
  color: var(--brand);
  font-size: 0.68rem;
}

@media (max-width: 768px) {
  .lang-extra { display: none; }
}

/* ======== 特性卡片区 ======== */
.features-grid {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: 1.5rem;
}

@media (max-width: 768px) {
  .features-grid { grid-template-columns: 1fr; }
}

.feature-card {
  background: var(--bg-card);
  border-radius: 20px;
  padding: 2rem;
  border: 1px solid var(--border);
  transition: transform 0.3s, box-shadow 0.3s;
  position: relative;
  overflow: hidden;
}

.feature-card:hover {
  transform: translateY(-4px);
  box-shadow: 0 12px 40px rgba(0, 0, 0, 0.06);
}

.feature-card-label {
  position: absolute;
  top: 0;
  right: 1.5rem;
  background: var(--brand);
  color: #fff;
  font-size: 0.68rem;
  font-weight: 600;
  padding: 0.2rem 0.65rem;
  border-radius: 0 0 8px 8px;
  letter-spacing: 0.05em;
}

.feature-card-icon {
  width: 48px;
  height: 48px;
  background: var(--brand-soft);
  border-radius: 14px;
  display: flex;
  align-items: center;
  justify-content: center;
  margin-bottom: 1.2rem;
}

.feature-card-icon i {
  font-size: 1.2rem;
  color: var(--brand);
}

.feature-card h3 {
  font-size: 1.05rem;
  font-weight: 700;
  margin-bottom: 0.5rem;
}

.feature-card p {
  font-size: 0.88rem;
  color: var(--text-secondary);
  line-height: 1.7;
}

/* ======== FAQ 卡片区 ======== */
.knowledge-grid {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: 1.25rem;
}

@media (max-width: 768px) {
  .knowledge-grid { grid-template-columns: 1fr; }
}

.knowledge-card {
  background: var(--bg-card);
  border-radius: 16px;
  padding: 1.5rem 1.8rem;
  border: 1px solid var(--border);
  transition: transform 0.3s, box-shadow 0.3s;
}

.knowledge-card:hover {
  transform: translateY(-3px);
  box-shadow: 0 8px 30px rgba(0, 0, 0, 0.05);
}

.knowledge-card h3 {
  font-size: 0.95rem;
  font-weight: 700;
  margin-bottom: 0.5rem;
}

.knowledge-card p {
  font-size: 0.85rem;
  color: var(--text-secondary);
  line-height: 1.7;
}

/* ======== 用户评价区 ======== */
.reviews-grid {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: 1.5rem;
}

@media (max-width: 768px) {
  .reviews-grid { grid-template-columns: 1fr; }
}

.review-card {
  background: var(--bg-card);
  border-radius: 20px;
  padding: 1.8rem;
  border: 1px solid var(--border);
  transition: transform 0.3s;
}

.review-card:hover {
  transform: translateY(-3px);
}

.review-stars {
  color: #FFC107;
  font-size: 0.9rem;
  margin-bottom: 0.8rem;
  letter-spacing: 2px;
}

.review-text {
  font-size: 0.88rem;
  color: var(--text-secondary);
  line-height: 1.7;
  margin-bottom: 1.2rem;
}

.review-user {
  display: flex;
  align-items: center;
  gap: 0.7rem;
}

.review-avatar {
  width: 36px;
  height: 36px;
  border-radius: 50%;
  object-fit: cover;
}

.review-name {
  font-size: 0.85rem;
  font-weight: 600;
}

.review-meta {
  font-size: 0.72rem;
  color: var(--text-muted);
}

/* ======== CTA 横幅 ======== */
.cta-banner {
  text-align: center;
  padding: 5rem 2rem;
  background: var(--brand);
  color: #fff;
}

.cta-banner h2 {
  font-size: 2.2rem;
  font-weight: 800;
  margin-bottom: 0.8rem;
}

.cta-banner p {
  font-size: 1rem;
  opacity: 0.85;
  margin-bottom: 2rem;
  max-width: 460px;
  margin-left: auto;
  margin-right: auto;
  line-height: 1.6;
}

.cta-banner .btn-white {
  display: inline-flex;
  align-items: center;
  gap: 0.5rem;
  background: #fff;
  color: var(--brand);
  padding: 0.9rem 2.5rem;
  border-radius: 100px;
  font-size: 0.95rem;
  font-weight: 700;
  text-decoration: none;
  transition: transform 0.2s, box-shadow 0.2s;
}

.cta-banner .btn-white:hover {
  transform: translateY(-2px);
  box-shadow: 0 8px 30px rgba(0, 0, 0, 0.15);
}

/* ======== 页脚 ======== */
footer {
  text-align: center;
  padding: 3rem 2rem;
  border-top: 1px solid var(--border);
  background: var(--bg-section);
}

.footer-brand {
  font-size: 0.88rem;
  font-weight: 600;
  color: var(--text);
  margin-bottom: 0.4rem;
}

.footer-info {
  font-size: 0.75rem;
  color: var(--text-muted);
  margin-bottom: 0.3rem;
}

.footer-copy {
  font-size: 0.72rem;
  color: var(--text-muted);
}

/* ======== 功能标签（首页用） ======== */
.hero-features {
  display: flex;
  justify-content: center;
  gap: 2rem;
  margin-top: 1rem;
  flex-wrap: wrap;
}

.hero-feature {
  display: flex;
  align-items: center;
  gap: 0.4rem;
  font-size: 0.82rem;
  color: var(--text-muted);
  font-weight: 500;
}

.hero-feature i {
  color: var(--brand);
  font-size: 0.75rem;
}