:root {
  color-scheme: dark;
  --canvas-primary: #000000;
  --canvas-secondary: #1c1c1e;
  --surface-primary: #1c1c1e;
  --surface-secondary: #2c2c2e;
  --surface-elevated: #3a3a3c;
  --separator: #404043;
  --text-primary: #ffffff;
  --text-secondary: #8e8e93;
  --text-tertiary: #636366;
  --accent: #bafd4f;
  --on-accent: #000000;
  --emphasis-surface: #111802;
  --emphasis-raised: #243208;
  --radius-sm: 12px;
  --radius-md: 16px;
  --radius-lg: 20px;
  --radius-hero: 28px;
  --page-gutter: clamp(20px, 5vw, 56px);
  --reading-width: 760px;
  --site-width: 1200px;
}

* {
  box-sizing: border-box;
}

html {
  background: var(--canvas-primary);
  scroll-behavior: smooth;
}

body {
  margin: 0;
  min-width: 320px;
  color: var(--text-primary);
  background: var(--canvas-primary);
  font-family: -apple-system, BlinkMacSystemFont, "SF Pro Text", "SF Pro Display", sans-serif;
  font-size: 16px;
  line-height: 1.7;
  text-rendering: optimizeLegibility;
  -webkit-font-smoothing: antialiased;
}

a {
  color: inherit;
  text-decoration-thickness: 1px;
  text-underline-offset: 0.2em;
}

a:hover {
  color: var(--accent);
}

button,
a {
  -webkit-tap-highlight-color: transparent;
}

:focus-visible {
  outline: 2px solid var(--accent);
  outline-offset: 4px;
}

.site-header {
  position: sticky;
  top: 0;
  z-index: 10;
  border-bottom: 1px solid color-mix(in srgb, var(--separator) 64%, transparent);
  background: color-mix(in srgb, var(--canvas-primary) 88%, transparent);
  -webkit-backdrop-filter: saturate(140%) blur(22px);
  backdrop-filter: saturate(140%) blur(22px);
}

.header-inner,
.page-shell {
  width: min(100%, var(--site-width));
  margin: 0 auto;
  padding-inline: var(--page-gutter);
}

.header-inner {
  min-height: 64px;
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 24px;
}

.brand {
  color: var(--text-primary);
  font-size: 19px;
  font-weight: 700;
  letter-spacing: -0.02em;
  text-decoration: none;
}

.site-nav {
  display: flex;
  align-items: center;
  gap: clamp(18px, 3vw, 36px);
}

.site-nav a {
  color: var(--text-secondary);
  font-size: 14px;
  font-weight: 600;
  text-decoration: none;
  white-space: nowrap;
}

.site-nav a[aria-current="page"] {
  color: var(--text-primary);
}

[data-nav-copy] {
  display: none;
}

body[data-language="zh"] [data-nav-copy="zh"],
body[data-language="en"] [data-nav-copy="en"] {
  display: inline;
}

.page-shell {
  padding-top: clamp(64px, 9vw, 112px);
  padding-bottom: 48px;
}

.reading-column {
  max-width: var(--reading-width);
}

.page-title {
  margin: 0;
  max-width: 680px;
  font-size: clamp(42px, 6vw, 64px);
  font-weight: 750;
  letter-spacing: -0.045em;
  line-height: 1.05;
}

.page-intro {
  margin: 24px 0 0;
  max-width: 640px;
  color: var(--text-secondary);
  font-size: clamp(18px, 2.2vw, 22px);
  line-height: 1.55;
}

.page-meta {
  margin: 18px 0 0;
  color: var(--text-tertiary);
  font-size: 14px;
}

.promise,
.contact-panel {
  position: relative;
  margin-top: clamp(40px, 6vw, 64px);
  padding: clamp(24px, 4vw, 36px);
  overflow: hidden;
  border: 1px solid var(--emphasis-raised);
  border-radius: var(--radius-lg);
  background: var(--emphasis-surface);
}

.promise::before,
.contact-panel::before {
  content: "";
  position: absolute;
  inset: 22px auto 22px 20px;
  width: 4px;
  border-radius: 999px;
  background: var(--accent);
}

.promise-content,
.contact-panel-content {
  padding-left: 20px;
}

.promise h2,
.contact-panel h2 {
  margin: 0;
  font-size: clamp(21px, 2.7vw, 26px);
  line-height: 1.25;
  letter-spacing: -0.025em;
}

.promise p,
.contact-panel p {
  margin: 12px 0 0;
  color: color-mix(in srgb, var(--text-primary) 72%, transparent);
  font-size: 16px;
}

.content-sections {
  margin-top: clamp(56px, 8vw, 88px);
}

.content-section {
  padding: 32px 0 36px;
  border-top: 1px solid color-mix(in srgb, var(--separator) 72%, transparent);
}

.content-section:first-child {
  padding-top: 0;
  border-top: 0;
}

.content-section h2 {
  margin: 0;
  font-size: clamp(23px, 3vw, 28px);
  line-height: 1.25;
  letter-spacing: -0.025em;
}

.content-section p {
  margin: 14px 0 0;
  color: var(--text-secondary);
}

.content-section ul {
  margin: 16px 0 0;
  padding-left: 1.2em;
  color: var(--text-secondary);
}

.content-section li + li {
  margin-top: 9px;
}

.content-section strong,
.faq-list summary {
  color: var(--text-primary);
}

.text-link {
  color: var(--accent);
  font-weight: 650;
}

.language-switch {
  display: inline-flex;
  gap: 4px;
  margin-top: 40px;
  padding: 4px;
  border: 1px solid color-mix(in srgb, var(--separator) 72%, transparent);
  border-radius: var(--radius-sm);
  background: var(--surface-primary);
}

.language-switch button {
  min-height: 36px;
  padding: 0 14px;
  border: 0;
  border-radius: 9px;
  color: var(--text-secondary);
  background: transparent;
  font: inherit;
  font-size: 14px;
  font-weight: 650;
  cursor: pointer;
}

.language-switch button[aria-pressed="true"] {
  color: var(--on-accent);
  background: var(--accent);
}

[data-copy] {
  display: none;
}

body[data-language="zh"] [data-copy="zh"],
body[data-language="en"] [data-copy="en"] {
  display: block;
}

.contact-action {
  display: inline-flex;
  min-height: 48px;
  margin-top: 22px;
  padding: 0 20px;
  align-items: center;
  justify-content: center;
  border-radius: var(--radius-sm);
  color: var(--on-accent);
  background: var(--accent);
  font-size: 15px;
  font-weight: 700;
  text-decoration: none;
}

.contact-action:hover {
  color: var(--on-accent);
  filter: brightness(0.94);
}

.faq-list {
  margin-top: clamp(56px, 8vw, 88px);
  border-top: 1px solid color-mix(in srgb, var(--separator) 72%, transparent);
}

.faq-list h2 {
  margin: 0;
  padding: 0 0 28px;
  font-size: clamp(25px, 3.4vw, 32px);
  letter-spacing: -0.03em;
}

.faq-list details {
  border-bottom: 1px solid color-mix(in srgb, var(--separator) 72%, transparent);
}

.faq-list summary {
  display: flex;
  min-height: 76px;
  align-items: center;
  justify-content: space-between;
  gap: 24px;
  list-style: none;
  font-size: 18px;
  font-weight: 650;
  cursor: pointer;
}

.faq-list summary::-webkit-details-marker {
  display: none;
}

.faq-list summary::after {
  content: "+";
  flex: 0 0 auto;
  color: var(--text-secondary);
  font-size: 24px;
  font-weight: 400;
}

.faq-list details[open] summary::after {
  content: "−";
}

.faq-list details p {
  margin: -8px 42px 28px 0;
  color: var(--text-secondary);
}

.site-footer {
  width: min(100%, var(--site-width));
  margin: 32px auto 0;
  padding: 32px var(--page-gutter) 44px;
  border-top: 1px solid color-mix(in srgb, var(--separator) 64%, transparent);
}

.footer-inner {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 24px;
  color: var(--text-tertiary);
  font-size: 13px;
}

.footer-inner a {
  color: var(--text-secondary);
}

@media (max-width: 680px) {
  .header-inner {
    min-height: 58px;
  }

  .site-nav {
    gap: 14px;
  }

  .site-nav a {
    font-size: 13px;
  }

  .page-shell {
    padding-top: 56px;
  }

  .page-title {
    font-size: 42px;
  }

  .promise::before,
  .contact-panel::before {
    left: 16px;
  }

  .promise-content,
  .contact-panel-content {
    padding-left: 16px;
  }

  .footer-inner {
    align-items: flex-start;
    flex-direction: column;
    gap: 8px;
  }
}

@media (max-width: 460px) {
  .brand {
    font-size: 17px;
  }

  .site-nav {
    gap: 10px;
  }

  .site-nav a {
    font-size: 12px;
  }
}

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