/*
 * 落地页视觉体系（index.html 及三个二级页共用）
 * ─ 色彩：复用 js/utils/tailwind.config.js 的品牌色。主 CTA 用 accent(#2563eb)，
 *         它在白底上的对比度为 5.1:1，满足 WCAG AA；品牌蓝 primary(#3b82f6) 只用于图标与点缀。
 * ─ 文字：墨色 #0f172a(主) / #475569(次) / #64748b(弱)，三级层级。
 * ─ 节奏：区块纵向留白 4rem(移动) → 6rem(桌面)，正文最大宽度 48rem。
 * ─ 圆角：卡片 1rem、按钮 .625rem、徽标 999px。
 * ─ 动效：仅 hover 200ms 过渡；prefers-reduced-motion 下全部关闭。
 */

:root {
  --lw-ink: #0f172a;
  --lw-ink-2: #475569;
  --lw-ink-3: #64748b;
  --lw-line: #e2e8f0;
  --lw-bg-soft: #f8fafc;
  --lw-brand: #3b82f6;
  --lw-accent: #2563eb;
  --lw-accent-strong: #1d4ed8;
  --lw-accent-soft: #eff6ff;
}

html {
  scroll-behavior: smooth;
}

body {
  color: var(--lw-ink);
  -webkit-font-smoothing: antialiased;
}

/* 锚点跳转预留吸顶导航的高度，避免标题被遮住 */
section[id] {
  scroll-margin-top: 5rem;
}

.lw-skip-link {
  position: absolute;
  left: -9999px;
  top: 0;
  z-index: 100;
  background: var(--lw-accent);
  color: #fff;
  padding: 0.5rem 1rem;
  border-radius: 0 0 0.5rem 0;
}

.lw-skip-link:focus {
  left: 0;
}

/* ===== 排版 ===== */
.lw-eyebrow {
  color: var(--lw-accent);
  font-size: 0.875rem;
  font-weight: 600;
  letter-spacing: 0.08em;
  text-transform: uppercase;
  margin-bottom: 0.75rem;
}

.lw-h1 {
  font-size: clamp(2rem, 5vw, 3.25rem);
  font-weight: 800;
  line-height: 1.15;
  letter-spacing: -0.02em;
}

.lw-h2 {
  font-size: clamp(1.5rem, 3.4vw, 2.25rem);
  font-weight: 700;
  line-height: 1.25;
  letter-spacing: -0.01em;
}

.lw-h3 {
  font-size: 1.125rem;
  font-weight: 600;
}

.lw-lead {
  color: var(--lw-ink-2);
  font-size: 1.0625rem;
  line-height: 1.75;
  margin-top: 1.25rem;
}

.lw-body {
  color: var(--lw-ink-2);
  line-height: 1.75;
  margin-top: 1rem;
}

.lw-mark {
  color: var(--lw-accent);
}

/* ===== 按钮 ===== */
.lw-btn {
  display: inline-flex;
  align-items: center;
  gap: 0.5rem;
  border-radius: 0.625rem;
  padding: 0.5rem 1rem;
  font-size: 0.9375rem;
  font-weight: 600;
  line-height: 1.5;
  transition: background-color 200ms ease, color 200ms ease, box-shadow 200ms ease;
  white-space: nowrap;
}

.lw-btn-lg {
  padding: 0.875rem 1.5rem;
  font-size: 1rem;
}

.lw-btn-primary {
  background: var(--lw-accent);
  color: #fff;
  box-shadow: 0 1px 2px rgba(15, 23, 42, 0.08);
}

.lw-btn-primary:hover {
  background: var(--lw-accent-strong);
}

.lw-btn-ghost {
  background: #fff;
  color: var(--lw-ink);
  border: 1px solid var(--lw-line);
}

.lw-btn-ghost:hover {
  border-color: var(--lw-accent);
  color: var(--lw-accent);
}

.lw-nav-link {
  color: var(--lw-ink-2);
  font-size: 0.9375rem;
  font-weight: 500;
  transition: color 200ms ease;
}

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

.lw-btn:focus-visible,
.lw-nav-link:focus-visible,
a:focus-visible,
button:focus-visible {
  outline: 2px solid var(--lw-accent);
  outline-offset: 2px;
  border-radius: 0.5rem;
}

/* ===== 区块 ===== */
.lw-section {
  padding: 4rem 0;
}

@media (min-width: 768px) {
  .lw-section {
    padding: 6rem 0;
  }
}

.lw-section-soft {
  background: var(--lw-bg-soft);
  border-top: 1px solid var(--lw-line);
  border-bottom: 1px solid var(--lw-line);
}

.lw-hero {
  padding: 3rem 0;
}

@media (min-width: 768px) {
  .lw-hero {
    padding: 5rem 0;
  }
}

.lw-section-head {
  max-width: 42rem;
  margin: 0 auto 3rem;
  text-align: center;
}

.lw-card {
  background: #fff;
  border: 1px solid var(--lw-line);
  border-radius: 1rem;
  padding: 1.5rem;
  transition: border-color 200ms ease, box-shadow 200ms ease;
}

.lw-card:hover {
  border-color: #cbd5e1;
  box-shadow: 0 12px 32px -16px rgba(15, 23, 42, 0.18);
}

/* 素材卡：内边距交给卡片内部结构，避免与 Tailwind 的 p-0 争优先级 */
.lw-card-flush {
  padding: 0;
  overflow: hidden;
  display: flex;
  flex-direction: column;
}

/* 导航栏 logo 比公共样式更紧凑，保持吸顶条纤细 */
.lw-nav .lw-logo {
  width: 4rem;
  height: 4rem;
}

.lw-nav .lw-brand-title {
  font-size: 1.5rem;
}

/* ===== 三步学习闭环 ===== */
.lw-steps {
  display: grid;
  gap: 1.5rem;
  max-width: 60rem;
  margin: 0 auto;
}

@media (min-width: 768px) {
  .lw-steps {
    grid-template-columns: repeat(3, 1fr);
  }
}

.lw-step {
  background: #fff;
  border: 1px solid var(--lw-line);
  border-radius: 1rem;
  padding: 1.75rem 1.5rem;
}

.lw-step-num {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  width: 2rem;
  height: 2rem;
  border-radius: 999px;
  background: var(--lw-accent-soft);
  color: var(--lw-accent);
  font-weight: 700;
  font-size: 0.9375rem;
  margin-bottom: 1rem;
}

.lw-loop-note {
  max-width: 42rem;
  margin: 2rem auto 0;
  text-align: center;
  color: var(--lw-ink-3);
  font-size: 0.9375rem;
  line-height: 1.7;
}

/* ===== 首屏练习界面示意（纯 CSS，无图片请求） ===== */
.lw-mock {
  background: #fff;
  border: 1px solid var(--lw-line);
  border-radius: 1.25rem;
  box-shadow: 0 24px 60px -28px rgba(15, 23, 42, 0.28);
  overflow: hidden;
  max-width: 32rem;
  margin: 0 auto;
}

.lw-mock-bar {
  display: flex;
  align-items: center;
  gap: 0.375rem;
  padding: 0.75rem 1rem;
  background: var(--lw-bg-soft);
  border-bottom: 1px solid var(--lw-line);
}

.lw-mock-dot {
  width: 0.5rem;
  height: 0.5rem;
  border-radius: 999px;
  background: #cbd5e1;
}

.lw-mock-title {
  margin-left: 0.5rem;
  color: var(--lw-ink-3);
  font-size: 0.75rem;
}

.lw-mock-body {
  padding: 1.5rem 1.25rem;
}

.lw-mock-player {
  display: flex;
  align-items: center;
  gap: 0.75rem;
}

.lw-mock-play {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  width: 2.5rem;
  height: 2.5rem;
  border-radius: 999px;
  background: var(--lw-accent);
  color: #fff;
  flex: none;
}

.lw-mock-wave {
  display: flex;
  align-items: center;
  gap: 3px;
  height: 1.5rem;
  flex: 1;
}

.lw-mock-wave i {
  display: block;
  width: 3px;
  border-radius: 999px;
  background: #bfdbfe;
}

.lw-mock-wave i:nth-child(1) { height: 30%; }
.lw-mock-wave i:nth-child(2) { height: 60%; }
.lw-mock-wave i:nth-child(3) { height: 100%; }
.lw-mock-wave i:nth-child(4) { height: 45%; }
.lw-mock-wave i:nth-child(5) { height: 80%; }
.lw-mock-wave i:nth-child(6) { height: 35%; }
.lw-mock-wave i:nth-child(7) { height: 65%; }

.lw-mock-loop {
  flex: none;
  color: var(--lw-accent);
  background: var(--lw-accent-soft);
  border-radius: 999px;
  padding: 0.25rem 0.625rem;
  font-size: 0.75rem;
  font-weight: 600;
}

.lw-mock-phonetic {
  margin-top: 1.25rem;
  color: var(--lw-ink-3);
  font-family: ui-monospace, SFMono-Regular, Menlo, monospace;
  font-size: 0.875rem;
  letter-spacing: 0.04em;
}

.lw-mock-slots {
  display: flex;
  flex-wrap: wrap;
  gap: 0.75rem;
  margin-top: 1rem;
}

.lw-mock-slot {
  min-width: 3rem;
  text-align: center;
  padding-bottom: 0.375rem;
  border-bottom: 2px solid #cbd5e1;
  font-size: 1.25rem;
  font-weight: 700;
  color: var(--lw-ink);
}

.lw-mock-slot.is-ok {
  color: #047857;
  border-bottom-color: #10b981;
}

.lw-mock-slot.is-active {
  border-bottom-color: var(--lw-accent);
}

.lw-mock-foot {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 1rem;
  margin-top: 1.5rem;
  padding-top: 1rem;
  border-top: 1px solid var(--lw-line);
  font-size: 0.8125rem;
  color: var(--lw-ink-3);
}

.lw-mock-ok {
  color: #047857;
  font-weight: 600;
}

.lw-mock-progress {
  display: block;
  width: 6rem;
  height: 0.375rem;
  border-radius: 999px;
  background: var(--lw-line);
  overflow: hidden;
}

.lw-mock-progress i {
  display: block;
  height: 100%;
  background: var(--lw-accent);
}

/* ===== CTA 卡片 ===== */
.lw-cta-card {
  background: linear-gradient(160deg, #eff6ff 0%, #ffffff 70%);
  border: 1px solid #bfdbfe;
  border-radius: 1rem;
  padding: 2rem;
  text-align: center;
}

/* ===== 页脚 ===== */
.lw-footer {
  background: #0f172a;
  color: #cbd5e1;
  padding: 3rem 0 2rem;
}

.lw-footer-title {
  color: #fff;
  font-size: 0.9375rem;
  font-weight: 600;
  margin-bottom: 0.875rem;
}

.lw-footer-link {
  display: block;
  color: #94a3b8;
  font-size: 0.875rem;
  padding: 0.25rem 0;
  transition: color 200ms ease;
}

.lw-footer-link:hover {
  color: #fff;
}

/* ===== 二级页（AI 学习 / 用户评价 / 联系我们） ===== */
.lw-subpage {
  padding: 3rem 0 4rem;
}

@media (min-width: 768px) {
  .lw-subpage {
    padding: 4rem 0 5rem;
  }
}

.lw-subpage-head {
  max-width: 44rem;
  margin: 0 auto 2.5rem;
  text-align: center;
}

.lw-prose {
  max-width: 44rem;
  margin: 0 auto;
  color: var(--lw-ink-2);
  line-height: 1.8;
}

.lw-prose h2 {
  color: var(--lw-ink);
  font-size: 1.25rem;
  font-weight: 700;
  margin-top: 2rem;
}

.lw-prose p {
  margin-top: 0.875rem;
}

.lw-badge {
  display: inline-block;
  background: #fffbeb;
  color: #b45309;
  border: 1px solid #fde68a;
  border-radius: 999px;
  padding: 0.25rem 0.75rem;
  font-size: 0.8125rem;
  font-weight: 600;
}

@media (prefers-reduced-motion: reduce) {
  html {
    scroll-behavior: auto;
  }

  .lw-btn,
  .lw-card,
  .lw-footer-link,
  .lw-nav-link {
    transition: none;
  }
}