/* ==========================================================================
   whatsapp网页版 指南站 · 全站样式
   说明：纯本地 CSS，不引用任何 CDN / 外部字体 / 第三方图标库
   配色方案切换：修改 <html data-theme="green|blue|mono">  即可
   ========================================================================== */

/* ---------- 1. 设计变量 ---------- */
:root {
  --brand: #25d366;
  --brand-strong: #128c7e;
  --brand-deep: #075e54;
  --brand-soft: #e9f7ef;
  --brand-line: #cdeada;

  --ink: #0d1b17;
  --ink-2: #3c4f48;
  --ink-3: #6d7f78;

  --bg: #ffffff;
  --bg-soft: #f6faf8;
  --bg-deep: #08211c;

  --line: #e3ebe7;
  --line-2: #eef4f1;

  --radius-sm: 10px;
  --radius: 16px;
  --radius-lg: 24px;

  --shadow-xs: 0 1px 2px rgba(7, 94, 84, 0.06);
  --shadow-sm: 0 2px 8px rgba(7, 94, 84, 0.06), 0 1px 2px rgba(7, 94, 84, 0.04);
  --shadow-md: 0 10px 32px rgba(7, 94, 84, 0.09);
  --shadow-lg: 0 24px 60px rgba(7, 94, 84, 0.13);

  --max: 1160px;
  --nav-h: 68px;

  --font: -apple-system, BlinkMacSystemFont, "Segoe UI", "PingFang SC",
    "Hiragino Sans GB", "Microsoft YaHei", "Helvetica Neue", Arial, sans-serif;
}

/* 方案 B：深海蓝 */
html[data-theme="blue"] {
  --brand: #3b82f6;
  --brand-strong: #2563eb;
  --brand-deep: #0b2b64;
  --brand-soft: #eaf2ff;
  --brand-line: #cfe0fb;
  --bg-soft: #f5f8ff;
  --bg-deep: #07203f;
}

/* 方案 C：墨绿极简 */
html[data-theme="mono"] {
  --brand: #1c6b52;
  --brand-strong: #14503d;
  --brand-deep: #0b2c22;
  --brand-soft: #edf3f0;
  --brand-line: #d7e3dd;
  --bg-soft: #f7f8f7;
  --bg-deep: #0c1512;
}

/* ---------- 2. 重置 ---------- */
*,
*::before,
*::after {
  box-sizing: border-box;
}

html {
  -webkit-text-size-adjust: 100%;
  scroll-behavior: smooth;
  scroll-padding-top: calc(var(--nav-h) + 16px);
}

body {
  margin: 0;
  font-family: var(--font);
  font-size: 16px;
  line-height: 1.75;
  color: var(--ink-2);
  background: var(--bg);
  -webkit-font-smoothing: antialiased;
  text-rendering: optimizeLegibility;
  overflow-x: hidden;
}

h1,
h2,
h3,
h4,
h5 {
  color: var(--ink);
  line-height: 1.3;
  margin: 0 0 0.5em;
  font-weight: 700;
  letter-spacing: -0.01em;
}

h1 {
  font-size: clamp(1.85rem, 4.6vw, 3rem);
  letter-spacing: -0.02em;
}
h2 {
  font-size: clamp(1.4rem, 2.8vw, 2rem);
}
h3 {
  font-size: clamp(1.1rem, 1.8vw, 1.3rem);
}
h4 {
  font-size: 1.02rem;
}

p {
  margin: 0 0 1em;
}

a {
  color: var(--brand-strong);
  text-decoration: none;
  transition: color 0.18s, opacity 0.18s;
}
a:hover {
  color: var(--brand-deep);
}

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

ul,
ol {
  margin: 0 0 1em;
  padding-left: 1.3em;
}
li {
  margin-bottom: 0.4em;
}

strong {
  color: var(--ink);
  font-weight: 650;
}

code {
  font-family: ui-monospace, SFMono-Regular, Menlo, Consolas, monospace;
  font-size: 0.9em;
  background: var(--brand-soft);
  color: var(--brand-deep);
  padding: 0.15em 0.45em;
  border-radius: 6px;
  word-break: break-word;
}

hr {
  border: 0;
  border-top: 1px solid var(--line);
  margin: 2.5rem 0;
}

:focus-visible {
  outline: 2px solid var(--brand-strong);
  outline-offset: 3px;
  border-radius: 4px;
}

/* ---------- 3. 布局工具 ---------- */
.container {
  width: 100%;
  max-width: var(--max);
  margin: 0 auto;
  padding: 0 20px;
}

.section {
  padding: 68px 0;
}
.section--tight {
  padding: 44px 0;
}
.section--soft {
  background: var(--bg-soft);
  border-top: 1px solid var(--line-2);
  border-bottom: 1px solid var(--line-2);
}

.section-head {
  max-width: 720px;
  margin: 0 auto 40px;
  text-align: center;
}
.section-head p {
  color: var(--ink-3);
  margin-bottom: 0;
}
.section-head--left {
  margin-left: 0;
  text-align: left;
}

.eyebrow {
  display: inline-block;
  font-size: 0.78rem;
  font-weight: 700;
  letter-spacing: 0.12em;
  text-transform: uppercase;
  color: var(--brand-strong);
  background: var(--brand-soft);
  border: 1px solid var(--brand-line);
  border-radius: 100px;
  padding: 4px 12px;
  margin-bottom: 14px;
}

.lead {
  font-size: 1.06rem;
  color: var(--ink-2);
}

.muted {
  color: var(--ink-3);
}

.grid {
  display: grid;
  gap: 20px;
}
.grid-2 {
  grid-template-columns: repeat(2, 1fr);
}
.grid-3 {
  grid-template-columns: repeat(3, 1fr);
}
.grid-4 {
  grid-template-columns: repeat(4, 1fr);
}

/* ---------- 4. 按钮 ---------- */
.btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: 8px;
  padding: 12px 24px;
  border-radius: 100px;
  font-size: 0.95rem;
  font-weight: 650;
  font-family: inherit;
  line-height: 1.4;
  border: 1px solid transparent;
  cursor: pointer;
  transition: transform 0.15s, box-shadow 0.2s, background 0.2s, color 0.2s,
    border-color 0.2s;
  white-space: nowrap;
}
.btn:active {
  transform: translateY(1px);
}
.btn svg {
  width: 18px;
  height: 18px;
  flex: none;
}

.btn--primary {
  background: var(--brand-strong);
  color: #fff;
  box-shadow: 0 6px 18px rgba(18, 140, 126, 0.24);
}
.btn--primary:hover {
  background: var(--brand-deep);
  color: #fff;
  box-shadow: 0 10px 24px rgba(18, 140, 126, 0.3);
}

.btn--ghost {
  background: #fff;
  color: var(--ink);
  border-color: var(--line);
  box-shadow: var(--shadow-xs);
}
.btn--ghost:hover {
  border-color: var(--brand-line);
  background: var(--brand-soft);
  color: var(--brand-deep);
}

.btn--sm {
  padding: 9px 18px;
  font-size: 0.88rem;
}

.btn-row {
  display: flex;
  flex-wrap: wrap;
  gap: 12px;
  margin-top: 26px;
}

/* ---------- 5. 顶部导航 ---------- */
.site-header {
  position: sticky;
  top: 0;
  z-index: 100;
  background: rgba(255, 255, 255, 0.88);
  backdrop-filter: saturate(180%) blur(14px);
  border-bottom: 1px solid var(--line-2);
}

.nav {
  display: flex;
  align-items: center;
  gap: 22px;
  height: var(--nav-h);
}

.brand {
  display: flex;
  align-items: center;
  gap: 10px;
  font-weight: 800;
  font-size: 1.02rem;
  color: var(--ink);
  letter-spacing: -0.01em;
  flex: none;
}
.brand:hover {
  color: var(--brand-deep);
}
.brand-mark {
  width: 34px;
  height: 34px;
  flex: none;
}

.nav-links {
  display: flex;
  align-items: center;
  gap: 4px;
  margin-left: auto;
  list-style: none;
  padding: 0;
  margin-bottom: 0;
}
.nav-links li {
  margin: 0;
}
.nav-links a {
  display: block;
  padding: 8px 13px;
  border-radius: 8px;
  font-size: 0.92rem;
  font-weight: 550;
  color: var(--ink-2);
}
.nav-links a:hover {
  background: var(--bg-soft);
  color: var(--brand-deep);
}
.nav-links a[aria-current="page"] {
  color: var(--brand-deep);
  background: var(--brand-soft);
  font-weight: 700;
}

.nav-cta {
  flex: none;
  margin-left: 8px;
}

.nav-toggle {
  display: none;
  width: 42px;
  height: 42px;
  margin-left: auto;
  background: #fff;
  border: 1px solid var(--line);
  border-radius: 10px;
  cursor: pointer;
  align-items: center;
  justify-content: center;
  padding: 0;
}
.nav-toggle span {
  display: block;
  width: 18px;
  height: 2px;
  background: var(--ink);
  border-radius: 2px;
  position: relative;
}
.nav-toggle span::before,
.nav-toggle span::after {
  content: "";
  position: absolute;
  left: 0;
  width: 18px;
  height: 2px;
  background: var(--ink);
  border-radius: 2px;
  transition: transform 0.2s, top 0.2s;
}
.nav-toggle span::before {
  top: -6px;
}
.nav-toggle span::after {
  top: 6px;
}

/* ---------- 6. 首屏 ---------- */
.hero {
  position: relative;
  overflow: hidden;
  padding: 64px 0 72px;
  background: linear-gradient(180deg, var(--bg-soft) 0%, #fff 78%);
}
.hero::before,
.hero::after {
  content: "";
  position: absolute;
  border-radius: 50%;
  filter: blur(70px);
  opacity: 0.5;
  pointer-events: none;
}
.hero::before {
  width: 380px;
  height: 380px;
  background: var(--brand-line);
  top: -140px;
  right: -100px;
}
.hero::after {
  width: 300px;
  height: 300px;
  background: #d8f0e4;
  bottom: -160px;
  left: -80px;
  opacity: 0.35;
}

.hero-inner {
  position: relative;
  z-index: 1;
  display: grid;
  grid-template-columns: 1.05fr 0.95fr;
  gap: 52px;
  align-items: center;
}

.hero h1 {
  margin-bottom: 18px;
}
.hero h1 em {
  font-style: normal;
  color: var(--brand-strong);
  position: relative;
  white-space: nowrap;
}
.hero p.lead {
  font-size: 1.08rem;
  max-width: 520px;
}

.hero-badges {
  display: flex;
  flex-wrap: wrap;
  gap: 8px 18px;
  margin-top: 28px;
  padding-top: 24px;
  border-top: 1px solid var(--brand-line);
  font-size: 0.87rem;
  color: var(--ink-3);
}
.hero-badges span {
  display: inline-flex;
  align-items: center;
  gap: 6px;
}
.hero-badges svg {
  width: 15px;
  height: 15px;
  color: var(--brand-strong);
  flex: none;
}

/* 浏览器窗口模拟 */
.window {
  background: #fff;
  border: 1px solid var(--line);
  border-radius: var(--radius-lg);
  box-shadow: var(--shadow-lg);
  overflow: hidden;
  transform: perspective(1200px) rotateY(-2deg) rotateX(1deg);
}
.window-bar {
  display: flex;
  align-items: center;
  gap: 8px;
  padding: 12px 16px;
  background: var(--bg-soft);
  border-bottom: 1px solid var(--line-2);
}
.window-dots {
  display: flex;
  gap: 6px;
}
.window-dots i {
  width: 10px;
  height: 10px;
  border-radius: 50%;
  background: #d7e2dc;
  display: block;
}
.window-dots i:first-child {
  background: #ffbdb4;
}
.window-dots i:nth-child(2) {
  background: #ffe0a3;
}
.window-dots i:nth-child(3) {
  background: #b6e5c8;
}
.window-url {
  flex: 1;
  font-size: 0.75rem;
  color: var(--ink-3);
  background: #fff;
  border: 1px solid var(--line-2);
  border-radius: 6px;
  padding: 3px 10px;
  text-align: center;
  overflow: hidden;
  text-overflow: ellipsis;
  white-space: nowrap;
}
.chat {
  padding: 18px 16px 22px;
  background: #eef6f1;
  min-height: 320px;
  display: flex;
  flex-direction: column;
  gap: 10px;
}
.bubble {
  max-width: 78%;
  padding: 9px 13px;
  border-radius: 12px;
  font-size: 0.84rem;
  line-height: 1.6;
  background: #fff;
  color: var(--ink-2);
  box-shadow: 0 1px 2px rgba(7, 94, 84, 0.07);
  border-bottom-left-radius: 4px;
}
.bubble--out {
  margin-left: auto;
  background: #d9fdd3;
  color: #10352a;
  border-bottom-left-radius: 12px;
  border-bottom-right-radius: 4px;
}
.bubble small {
  display: block;
  font-size: 0.66rem;
  color: var(--ink-3);
  margin-top: 3px;
  text-align: right;
}
.chat-input {
  margin-top: auto;
  display: flex;
  align-items: center;
  gap: 8px;
  background: #fff;
  border-radius: 100px;
  padding: 7px 8px 7px 16px;
  box-shadow: 0 1px 3px rgba(7, 94, 84, 0.08);
  font-size: 0.8rem;
  color: var(--ink-3);
}
.chat-input b {
  margin-left: auto;
  width: 30px;
  height: 30px;
  border-radius: 50%;
  background: var(--brand-strong);
  display: grid;
  place-items: center;
  flex: none;
}
.chat-input b svg {
  width: 15px;
  height: 15px;
  color: #fff;
}

/* ---------- 7. 卡片 ---------- */
.card {
  background: #fff;
  border: 1px solid var(--line);
  border-radius: var(--radius);
  padding: 26px 24px;
  box-shadow: var(--shadow-xs);
  transition: transform 0.22s, box-shadow 0.22s, border-color 0.22s;
  height: 100%;
}
.card:hover {
  transform: translateY(-3px);
  box-shadow: var(--shadow-md);
  border-color: var(--brand-line);
}
.card h3 {
  margin-bottom: 8px;
  font-size: 1.08rem;
}
.card p {
  margin-bottom: 0;
  font-size: 0.94rem;
  color: var(--ink-3);
}
.card p + p {
  margin-top: 0.8em;
}

.icon-box {
  width: 44px;
  height: 44px;
  border-radius: 12px;
  display: grid;
  place-items: center;
  background: var(--brand-soft);
  color: var(--brand-strong);
  margin-bottom: 16px;
  flex: none;
}
.icon-box svg {
  width: 22px;
  height: 22px;
}

.card--flat {
  box-shadow: none;
  background: var(--bg-soft);
}
.card--flat:hover {
  transform: none;
  box-shadow: none;
}

/* 带左侧强调线的条目 */
.fact {
  display: flex;
  gap: 14px;
  padding: 18px 0;
  border-bottom: 1px solid var(--line-2);
}
.fact:last-child {
  border-bottom: 0;
}
.fact-dot {
  width: 8px;
  height: 8px;
  border-radius: 50%;
  background: var(--brand);
  margin-top: 10px;
  flex: none;
}
.fact h4 {
  margin: 0 0 4px;
}
.fact p {
  margin: 0;
  font-size: 0.93rem;
  color: var(--ink-3);
}

/* ---------- 8. 步骤 ---------- */
.steps {
  counter-reset: step;
  display: grid;
  gap: 18px;
}
.step {
  position: relative;
  display: flex;
  gap: 18px;
  background: #fff;
  border: 1px solid var(--line);
  border-radius: var(--radius);
  padding: 24px;
  box-shadow: var(--shadow-xs);
}
.step-num {
  counter-increment: step;
  flex: none;
  width: 40px;
  height: 40px;
  border-radius: 50%;
  background: var(--brand-soft);
  color: var(--brand-deep);
  border: 1px solid var(--brand-line);
  display: grid;
  place-items: center;
  font-weight: 800;
  font-size: 0.98rem;
}
.step-num::before {
  content: counter(step);
}
.step-body h3 {
  margin: 2px 0 6px;
  font-size: 1.05rem;
}
.step-body p {
  margin: 0;
  font-size: 0.95rem;
  color: var(--ink-3);
}
.step-body p + p {
  margin-top: 0.6em;
}

/* ---------- 9. 表格 ---------- */
.table-wrap {
  overflow-x: auto;
  border: 1px solid var(--line);
  border-radius: var(--radius);
  background: #fff;
  box-shadow: var(--shadow-xs);
  -webkit-overflow-scrolling: touch;
}
table {
  width: 100%;
  border-collapse: collapse;
  font-size: 0.92rem;
  min-width: 560px;
}
th,
td {
  padding: 14px 18px;
  text-align: left;
  border-bottom: 1px solid var(--line-2);
  vertical-align: top;
}
th {
  background: var(--bg-soft);
  font-weight: 700;
  color: var(--ink);
  font-size: 0.86rem;
  letter-spacing: 0.01em;
  white-space: nowrap;
}
tbody tr:last-child td {
  border-bottom: 0;
}
tbody tr:hover td {
  background: #fbfdfc;
}
td strong {
  color: var(--ink);
}

/* ---------- 10. FAQ 手风琴 ---------- */
.faq-list {
  display: grid;
  gap: 12px;
  max-width: 860px;
  margin: 0 auto;
}
details.faq {
  background: #fff;
  border: 1px solid var(--line);
  border-radius: 14px;
  padding: 0 22px;
  box-shadow: var(--shadow-xs);
  transition: border-color 0.2s, box-shadow 0.2s;
}
details.faq[open] {
  border-color: var(--brand-line);
  box-shadow: var(--shadow-sm);
}
details.faq summary {
  list-style: none;
  cursor: pointer;
  padding: 18px 30px 18px 0;
  font-weight: 650;
  color: var(--ink);
  font-size: 0.99rem;
  position: relative;
  line-height: 1.6;
}
details.faq summary::-webkit-details-marker {
  display: none;
}
details.faq summary::after {
  content: "";
  position: absolute;
  right: 2px;
  top: 50%;
  width: 8px;
  height: 8px;
  border-right: 2px solid var(--ink-3);
  border-bottom: 2px solid var(--ink-3);
  transform: translateY(-70%) rotate(45deg);
  transition: transform 0.2s;
}
details.faq[open] summary::after {
  transform: translateY(-30%) rotate(-135deg);
  border-color: var(--brand-strong);
}
details.faq .faq-body {
  padding: 0 0 20px;
  font-size: 0.95rem;
  color: var(--ink-2);
  border-top: 1px solid var(--line-2);
  padding-top: 16px;
  margin-top: 2px;
}
details.faq .faq-body p:last-child {
  margin-bottom: 0;
}

/* ---------- 11. 提示框 ---------- */
.note {
  display: flex;
  gap: 14px;
  padding: 18px 20px;
  border-radius: 14px;
  background: var(--brand-soft);
  border: 1px solid var(--brand-line);
  font-size: 0.94rem;
  color: var(--ink-2);
  margin: 22px 0;
}
.note svg {
  width: 20px;
  height: 20px;
  flex: none;
  color: var(--brand-strong);
  margin-top: 3px;
}
.note p:last-child {
  margin-bottom: 0;
}
.note--warn {
  background: #fff8ec;
  border-color: #f6e2bd;
}
.note--warn svg {
  color: #b57d17;
}

/* ---------- 12. 面包屑 ---------- */
.crumbs {
  font-size: 0.82rem;
  color: var(--ink-3);
  padding: 18px 0 0;
}
.crumbs ol {
  display: flex;
  flex-wrap: wrap;
  gap: 6px;
  list-style: none;
  margin: 0;
  padding: 0;
}
.crumbs li {
  margin: 0;
  display: flex;
  align-items: center;
  gap: 6px;
}
.crumbs li + li::before {
  content: "/";
  color: var(--line);
}
.crumbs a {
  color: var(--ink-3);
}
.crumbs a:hover {
  color: var(--brand-strong);
}
.crumbs [aria-current] {
  color: var(--ink-2);
}

/* ---------- 13. 页面标题区 ---------- */
.page-head {
  padding: 26px 0 8px;
}
.page-head h1 {
  margin-bottom: 14px;
}
.page-head .lead {
  max-width: 760px;
  font-size: 1.04rem;
  color: var(--ink-3);
  margin-bottom: 0;
}

/* ---------- 14. 文章正文 ---------- */
.prose {
  max-width: 800px;
}
.prose h2 {
  margin-top: 44px;
  padding-top: 8px;
}
.prose h2:first-child {
  margin-top: 0;
}
.prose h3 {
  margin-top: 30px;
}
.prose p,
.prose li {
  color: var(--ink-2);
}
.prose ul,
.prose ol {
  margin-bottom: 1.2em;
}
.prose li {
  margin-bottom: 0.5em;
}
.prose blockquote {
  margin: 24px 0;
  padding: 4px 0 4px 20px;
  border-left: 3px solid var(--brand-line);
  color: var(--ink-3);
}

.two-col {
  display: grid;
  grid-template-columns: 250px 1fr;
  gap: 52px;
  align-items: start;
}
.toc {
  position: sticky;
  top: calc(var(--nav-h) + 24px);
  font-size: 0.88rem;
  border-left: 2px solid var(--line-2);
  padding-left: 16px;
}
.toc h4 {
  font-size: 0.78rem;
  text-transform: uppercase;
  letter-spacing: 0.08em;
  color: var(--ink-3);
  margin-bottom: 10px;
}
.toc ul {
  list-style: none;
  padding: 0;
  margin: 0;
}
.toc li {
  margin: 0;
}
.toc a {
  display: block;
  padding: 4px 0;
  color: var(--ink-3);
  font-size: 0.87rem;
}
.toc a:hover {
  color: var(--brand-strong);
}

/* ---------- 15. 统计条 ---------- */
.stats {
  display: grid;
  grid-template-columns: repeat(4, 1fr);
  gap: 1px;
  background: var(--line);
  border: 1px solid var(--line);
  border-radius: var(--radius);
  overflow: hidden;
}
.stat {
  background: #fff;
  padding: 24px 20px;
  text-align: center;
}
.stat b {
  display: block;
  font-size: 1.5rem;
  color: var(--brand-deep);
  font-weight: 800;
  letter-spacing: -0.02em;
  line-height: 1.2;
}
.stat span {
  font-size: 0.83rem;
  color: var(--ink-3);
}

/* ---------- 16. CTA 区块 ---------- */
.cta {
  background: linear-gradient(135deg, var(--brand-deep), #0c3f37);
  border-radius: var(--radius-lg);
  padding: 52px 44px;
  color: #fff;
  text-align: center;
  position: relative;
  overflow: hidden;
}
html[data-theme="blue"] .cta {
  background: linear-gradient(135deg, #0b2b64, #123f7d);
}
html[data-theme="mono"] .cta {
  background: linear-gradient(135deg, #0b2c22, #113b2e);
}
.cta::after {
  content: "";
  position: absolute;
  width: 320px;
  height: 320px;
  border-radius: 50%;
  background: rgba(255, 255, 255, 0.06);
  top: -140px;
  right: -80px;
}
.cta h2 {
  color: #fff;
  margin-bottom: 12px;
  position: relative;
}
.cta p {
  color: rgba(255, 255, 255, 0.78);
  max-width: 560px;
  margin: 0 auto;
  position: relative;
}
.cta .btn-row {
  justify-content: center;
  position: relative;
}
.cta .btn--primary {
  background: #fff;
  color: var(--brand-deep);
  box-shadow: 0 8px 24px rgba(0, 0, 0, 0.16);
}
.cta .btn--primary:hover {
  background: var(--brand-soft);
  color: var(--brand-deep);
}
.cta .btn--ghost {
  background: transparent;
  color: #fff;
  border-color: rgba(255, 255, 255, 0.35);
}
.cta .btn--ghost:hover {
  background: rgba(255, 255, 255, 0.1);
  color: #fff;
  border-color: rgba(255, 255, 255, 0.6);
}

/* ---------- 17. 页脚 ---------- */
.site-footer {
  background: var(--bg-deep);
  color: rgba(255, 255, 255, 0.62);
  padding: 56px 0 0;
  margin-top: 72px;
  font-size: 0.9rem;
}
.footer-grid {
  display: grid;
  grid-template-columns: 1.6fr 1fr 1fr 1fr;
  gap: 40px;
  padding-bottom: 44px;
}
.site-footer .brand {
  color: #fff;
  margin-bottom: 14px;
}
.site-footer .brand:hover {
  color: #fff;
}
.footer-about p {
  max-width: 300px;
  font-size: 0.87rem;
  color: rgba(255, 255, 255, 0.55);
  line-height: 1.8;
}
.footer-col h4 {
  color: #fff;
  font-size: 0.85rem;
  letter-spacing: 0.06em;
  text-transform: uppercase;
  margin-bottom: 14px;
  opacity: 0.9;
}
.footer-col ul {
  list-style: none;
  padding: 0;
  margin: 0;
}
.footer-col li {
  margin-bottom: 9px;
}
.footer-col a {
  color: rgba(255, 255, 255, 0.6);
}
.footer-col a:hover {
  color: #fff;
}
.footer-bottom {
  border-top: 1px solid rgba(255, 255, 255, 0.1);
  padding: 20px 0 26px;
  display: flex;
  flex-wrap: wrap;
  gap: 10px 24px;
  align-items: center;
  justify-content: space-between;
  font-size: 0.82rem;
  color: rgba(255, 255, 255, 0.42);
}
.footer-bottom a {
  color: rgba(255, 255, 255, 0.55);
}
.footer-bottom a:hover {
  color: #fff;
}

/* ---------- 18. 回到顶部 ---------- */
.to-top {
  position: fixed;
  right: 22px;
  bottom: 22px;
  width: 44px;
  height: 44px;
  border-radius: 50%;
  background: #fff;
  border: 1px solid var(--line);
  box-shadow: var(--shadow-md);
  display: grid;
  place-items: center;
  cursor: pointer;
  opacity: 0;
  visibility: hidden;
  transform: translateY(10px);
  transition: opacity 0.25s, transform 0.25s, visibility 0.25s;
  z-index: 90;
  padding: 0;
}
.to-top.is-visible {
  opacity: 1;
  visibility: visible;
  transform: none;
}
.to-top svg {
  width: 18px;
  height: 18px;
  color: var(--ink-2);
}
.to-top:hover {
  border-color: var(--brand-line);
  background: var(--brand-soft);
}

/* ---------- 19. 滚动进入动画 ---------- */
.reveal {
  opacity: 0;
  transform: translateY(16px);
  transition: opacity 0.5s ease, transform 0.5s ease;
}
.reveal.is-in {
  opacity: 1;
  transform: none;
}

@media (prefers-reduced-motion: reduce) {
  html {
    scroll-behavior: auto;
  }
  *,
  *::before,
  *::after {
    animation-duration: 0.001ms !important;
    transition-duration: 0.001ms !important;
  }
  .reveal {
    opacity: 1;
    transform: none;
  }
}

/* ---------- 20. 404 ---------- */
.error-page {
  text-align: center;
  padding: 90px 0 60px;
}
.error-code {
  font-size: clamp(4.5rem, 16vw, 9rem);
  font-weight: 800;
  line-height: 1;
  letter-spacing: -0.05em;
  background: linear-gradient(160deg, var(--brand), var(--brand-deep));
  -webkit-background-clip: text;
  background-clip: text;
  color: transparent;
  margin-bottom: 8px;
}
.error-page p {
  color: var(--ink-3);
  max-width: 460px;
  margin: 0 auto 26px;
}
.error-links {
  display: flex;
  flex-wrap: wrap;
  gap: 10px;
  justify-content: center;
  margin-top: 34px;
  padding-top: 28px;
  border-top: 1px solid var(--line-2);
  max-width: 700px;
  margin-left: auto;
  margin-right: auto;
}
.error-links a {
  font-size: 0.9rem;
  padding: 8px 16px;
  border: 1px solid var(--line);
  border-radius: 100px;
  background: #fff;
  color: var(--ink-2);
}
.error-links a:hover {
  border-color: var(--brand-line);
  background: var(--brand-soft);
  color: var(--brand-deep);
}

/* ---------- 21. 响应式 ---------- */
@media (max-width: 1000px) {
  .hero-inner {
    grid-template-columns: 1fr;
    gap: 40px;
  }
  .window {
    transform: none;
    max-width: 520px;
  }
  .grid-4 {
    grid-template-columns: repeat(2, 1fr);
  }
  .two-col {
    grid-template-columns: 1fr;
    gap: 32px;
  }
  .toc {
    position: static;
    border-left: 0;
    border-top: 1px solid var(--line-2);
    padding: 16px 0 0;
  }
  .footer-grid {
    grid-template-columns: 1fr 1fr;
    gap: 32px;
  }
}

@media (max-width: 820px) {
  .nav-toggle {
    display: flex;
  }
  .nav-links {
    position: absolute;
    top: var(--nav-h);
    left: 0;
    right: 0;
    background: #fff;
    flex-direction: column;
    align-items: stretch;
    gap: 2px;
    padding: 12px 20px 20px;
    border-bottom: 1px solid var(--line);
    box-shadow: var(--shadow-md);
    margin: 0;
    display: none;
  }
  .nav-links.is-open {
    display: flex;
  }
  .nav-links a {
    padding: 11px 12px;
    font-size: 0.95rem;
  }
  .nav-cta {
    display: none;
  }
  .section {
    padding: 52px 0;
  }
  .hero {
    padding: 44px 0 52px;
  }
  .grid-3 {
    grid-template-columns: 1fr 1fr;
  }
  .stats {
    grid-template-columns: 1fr 1fr;
  }
  .cta {
    padding: 40px 24px;
  }
}

@media (max-width: 560px) {
  body {
    font-size: 15.5px;
  }
  .grid-2,
  .grid-3,
  .grid-4 {
    grid-template-columns: 1fr;
  }
  .footer-grid {
    grid-template-columns: 1fr;
  }
  .step {
    flex-direction: column;
    gap: 12px;
    padding: 20px;
  }
  .hero-badges {
    gap: 8px 14px;
  }
  .to-top {
    right: 14px;
    bottom: 14px;
  }
  .cta {
    border-radius: var(--radius);
  }
}

/* ---------- 22. 打印 ---------- */
@media print {
  .site-header,
  .site-footer,
  .to-top,
  .cta,
  .nav-toggle {
    display: none !important;
  }
  body {
    color: #000;
  }
  .card,
  .window {
    box-shadow: none;
    border: 1px solid #ccc;
  }
}