:root {
  --bg: #fff;
  --fg: #1c1c1c;
  --page: #f3f3f5;
  --muted: color-mix(in srgb, var(--fg) 55%, transparent);
  --elev: color-mix(in srgb, var(--fg) 6%, var(--bg));
  --line: color-mix(in srgb, var(--fg) 12%, transparent);
  --hover: color-mix(in srgb, var(--fg) 8%, transparent);
  --accent: var(--fg);
  --on-accent: var(--bg);
  --ok: #22c55e;
  --blue: #2563eb;
  --green: #16a34a;
  --rose: #e11d48;
  --r: 12px;
  --r-lg: 16px;
  --r-xl: 18px;
  --rail: 264px;
  --title: 36px;
  --font: 'Segoe UI Variable Text', 'Segoe UI', 'PingFang SC', 'Microsoft YaHei UI',
    'Noto Sans SC', sans-serif;
  --mono: ui-monospace, 'Cascadia Code', 'SF Mono', Consolas, monospace;
  --shadow-sm: 0 8px 22px color-mix(in srgb, #000 8%, transparent);
  --shadow: 0 16px 48px color-mix(in srgb, #000 12%, transparent);
  --motion: 180ms cubic-bezier(0.22, 1, 0.36, 1);
  --nav: 56px;
  --max: 1120px;
}

html[data-theme='dark'] {
  --bg: #141414;
  --fg: #f2f2f2;
  --page: #0c0c0c;
  --shadow-sm: 0 8px 22px color-mix(in srgb, #000 45%, transparent);
  --shadow: 0 16px 48px color-mix(in srgb, #000 55%, transparent);
}

*,
*::before,
*::after {
  box-sizing: border-box;
}

html {
  scroll-behavior: smooth;
  overflow-x: hidden;
}

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

  *,
  *::before,
  *::after {
    animation: none !important;
    transition: none !important;
  }
}

body {
  margin: 0;
  color: var(--fg);
  background: var(--page);
  font-family: var(--font);
  font-size: 15px;
  line-height: 1.5;
  letter-spacing: -0.01em;
  min-height: 100vh;
  overflow-x: hidden;
}

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

button,
input,
textarea,
select {
  font: inherit;
  color: inherit;
}

button {
  cursor: pointer;
}

a {
  color: inherit;
  text-decoration: none;
}

:focus-visible {
  outline: 2px solid color-mix(in srgb, var(--fg) 55%, transparent);
  outline-offset: 2px;
}

.skip {
  position: absolute;
  left: 12px;
  top: -40px;
  z-index: 80;
  padding: 8px 12px;
  border-radius: 8px;
  background: var(--fg);
  color: var(--bg);
}

.skip:focus {
  top: 12px;
}

.site-nav {
  position: sticky;
  top: 0;
  z-index: 40;
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 16px;
  height: var(--nav);
  padding: 0 20px;
  background: color-mix(in srgb, var(--bg) 86%, transparent);
  border-bottom: 1px solid var(--line);
  backdrop-filter: blur(18px) saturate(1.4);
  -webkit-backdrop-filter: blur(18px) saturate(1.4);
}

.brand {
  display: flex;
  align-items: center;
  gap: 10px;
  font-weight: 620;
  letter-spacing: -0.03em;
  flex-shrink: 0;
}

.brand-mark {
  width: 28px;
  height: 28px;
  border-radius: 8px;
  object-fit: cover;
  background: #fff;
  box-shadow: 0 1px 0 color-mix(in srgb, var(--fg) 14%, transparent);
}

.nav-links {
  display: flex;
  align-items: center;
  gap: 4px;
  margin-left: 8px;
}

.nav-links a {
  padding: 6px 10px;
  border-radius: 8px;
  color: var(--muted);
  font-size: 13px;
  font-weight: 550;
}

.nav-links a:hover {
  color: var(--fg);
  background: var(--hover);
}

.nav-tools {
  margin-left: auto;
  display: flex;
  align-items: center;
  gap: 8px;
  flex-shrink: 0;
}

.lang-switch,
.lang-compact,
.theme-btn,
.menu-btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  height: 32px;
  border: 1px solid var(--line);
  background: var(--bg);
  border-radius: 999px;
}

.lang-compact {
  display: none;
  min-width: 40px;
  padding: 0 10px;
  color: var(--fg);
  font-size: 12px;
  font-weight: 620;
}

.lang-switch {
  padding: 2px;
  gap: 0;
}

.lang-switch button {
  height: 26px;
  min-width: 32px;
  padding: 0 10px;
  border: 0;
  background: transparent;
  border-radius: 999px;
  color: var(--muted);
  font-size: 12px;
  font-weight: 620;
}

.lang-switch button[aria-pressed='true'] {
  background: var(--fg);
  color: var(--bg);
}

.theme-btn,
.menu-btn {
  width: 32px;
  padding: 0;
  color: var(--muted);
}

.theme-btn:hover,
.menu-btn:hover {
  color: var(--fg);
  background: var(--hover);
}

.theme-btn svg,
.menu-btn svg {
  width: 16px;
  height: 16px;
}

.btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: 8px;
  height: 36px;
  padding: 0 16px;
  border: 0;
  border-radius: 999px;
  background: var(--fg);
  color: var(--bg);
  font-size: 13px;
  font-weight: 600;
  letter-spacing: -0.02em;
  transition: transform var(--motion), background var(--motion);
}

.btn:hover {
  background: color-mix(in srgb, var(--fg) 88%, var(--bg));
}

.btn-ghost {
  background: var(--elev);
  color: var(--fg);
  border: 1px solid var(--line);
}

.btn-ghost:hover {
  background: var(--hover);
}

.btn-lg {
  height: 42px;
  padding: 0 18px;
  font-size: 14px;
}

.menu-btn {
  display: none;
}

.mobile-nav {
  display: none;
}

.hero {
  padding: 28px 20px 8px;
}

.og-window {
  max-width: var(--max);
  margin: 0 auto;
  border-radius: var(--r);
  background: var(--bg);
  border: 1px solid var(--line);
  box-shadow: var(--shadow);
  overflow: hidden;
}

.og-titlebar {
  display: flex;
  align-items: center;
  height: var(--title);
  padding-left: 16px;
  border-bottom: 1px solid var(--line);
  font-size: 12px;
  font-weight: 620;
  letter-spacing: 0.02em;
}

.og-titlebar span {
  min-width: 0;
  overflow: hidden;
  text-overflow: ellipsis;
  white-space: nowrap;
}

.og-win {
  margin-left: auto;
  display: flex;
  height: 100%;
}

.og-win button {
  width: 46px;
  height: 100%;
  padding: 0;
  border: 0;
  background: transparent;
  color: var(--muted);
  position: relative;
}

.og-win button::before,
.og-win button::after {
  content: '';
  position: absolute;
  inset: 50% auto auto 50%;
  background: currentColor;
}

.og-win button[data-win='min']::before {
  width: 10px;
  height: 1px;
  transform: translate(-50%, -50%);
}

.og-win button[data-win='max']::before {
  width: 10px;
  height: 10px;
  background: transparent;
  border: 1px solid currentColor;
  transform: translate(-50%, -50%);
}

.og-win button[data-win='close']::before,
.og-win button[data-win='close']::after {
  width: 12px;
  height: 1px;
}

.og-win button[data-win='close']::before {
  transform: translate(-50%, -50%) rotate(45deg);
}

.og-win button[data-win='close']::after {
  transform: translate(-50%, -50%) rotate(-45deg);
}

.og-win button:hover {
  background: var(--hover);
  color: var(--fg);
}

.og-win button[data-win='close']:hover {
  background: #e5484d;
  color: #fff;
}

.og-shell {
  display: grid;
  grid-template-columns: var(--rail) minmax(0, 1fr);
  min-height: 640px;
}

.og-rail {
  display: flex;
  flex-direction: column;
  min-height: 0;
  padding: 12px 10px 10px;
  border-right: 1px solid var(--line);
  background: var(--bg);
}

.rail-brand {
  display: flex;
  align-items: center;
  gap: 8px;
  padding: 4px 8px 12px;
  font-size: 14px;
  font-weight: 650;
  letter-spacing: -0.03em;
}

.rail-brand img,
.rail-brand svg {
  width: 22px;
  height: 22px;
  border-radius: 6px;
  color: var(--fg);
}

.rail-item {
  display: flex;
  align-items: center;
  gap: 10px;
  width: 100%;
  height: 36px;
  padding: 0 12px;
  border: 0;
  border-radius: 10px;
  background: transparent;
  color: var(--fg);
  font-size: 13px;
  font-weight: 550;
  text-align: left;
}

.rail-item svg {
  width: 16px;
  height: 16px;
  flex-shrink: 0;
}

.rail-item.active {
  background: var(--fg);
  color: var(--bg);
}

.rail-item:not(.active):hover {
  background: var(--hover);
}

.rail-label {
  margin: 14px 12px 6px;
  color: var(--muted);
  font-size: 11px;
  font-weight: 600;
  letter-spacing: 0.04em;
}

.rail-folder {
  background: var(--elev);
  font-weight: 600;
}

.rail-search {
  display: flex;
  align-items: center;
  gap: 8px;
  height: 36px;
  margin: 4px 0 8px;
  padding: 0 12px;
  border-radius: 10px;
  background: var(--elev);
  color: var(--muted);
  font-size: 13px;
}

.rail-search svg {
  width: 14px;
  height: 14px;
}

.rail-list {
  flex: 1;
  min-height: 0;
  overflow: auto;
  padding: 2px 0;
}

.rail-chat {
  display: block;
  width: 100%;
  padding: 8px 12px;
  border: 0;
  border-radius: 8px;
  background: transparent;
  color: var(--muted);
  font-size: 13px;
  text-align: left;
  white-space: nowrap;
  overflow: hidden;
  text-overflow: ellipsis;
}

.rail-chat:hover {
  background: var(--hover);
  color: var(--fg);
}

.rail-user {
  display: flex;
  align-items: center;
  gap: 10px;
  margin-top: 8px;
  padding: 8px 8px 4px;
  border-top: 1px solid var(--line);
}

.rail-avatar {
  width: 28px;
  height: 28px;
  border-radius: 999px;
  display: grid;
  place-items: center;
  background: var(--elev);
  color: var(--fg);
}

.rail-avatar svg {
  width: 16px;
  height: 16px;
}

.rail-user strong {
  display: block;
  font-size: 13px;
  font-weight: 620;
}

.rail-user em {
  color: var(--muted);
  font-style: normal;
  font-size: 12px;
}

.rail-user .theme-btn {
  margin-left: auto;
}

.og-main {
  position: relative;
  display: flex;
  flex-direction: column;
  min-width: 0;
  overflow: hidden;
  background:
    radial-gradient(1100px 720px at 50% -8%, color-mix(in srgb, var(--fg) 6%, transparent), transparent 58%),
    var(--bg);
}

.og-home {
  flex: 1;
  display: flex;
  flex-direction: column;
  justify-content: center;
  align-items: center;
  gap: 14px;
  padding: 3vh 32px 12px;
  width: 100%;
  min-width: 0;
}

.og-home-mark {
  color: var(--fg);
  line-height: 0;
  width: min(460px, 86%);
  max-width: 100%;
  min-width: 0;
  overflow: hidden;
}

.og-home-mark svg {
  width: 100%;
  max-width: 100%;
  height: auto;
}

.og-home h1 {
  margin: 0;
  font-size: clamp(22px, 3vw, 28px);
  font-weight: 560;
  letter-spacing: -0.045em;
  text-align: center;
}

.og-home-hint {
  margin: 0 0 4px;
  max-width: min(440px, 100%);
  padding: 0 16px;
  text-align: center;
  color: var(--muted);
  font-size: 13px;
  line-height: 1.5;
}

.og-cards {
  display: grid;
  grid-template-columns: repeat(2, minmax(0, 1fr));
  gap: 10px;
  width: min(520px, 100%);
  margin-top: 8px;
}

.og-card {
  display: flex;
  flex-direction: column;
  align-items: flex-start;
  gap: 18px;
  min-height: 108px;
  padding: 16px;
  text-align: left;
  border-radius: var(--r-lg);
  border: 1px solid var(--line);
  background: var(--bg);
  box-shadow: var(--shadow-sm);
  color: var(--fg);
  transition: transform var(--motion), background var(--motion), border-color var(--motion);
}

button.og-card {
  appearance: none;
}

.og-card:hover {
  background: color-mix(in srgb, var(--fg) 4%, var(--bg));
  transform: translateY(-2px);
}

.og-card-icon {
  width: 28px;
  height: 28px;
  display: grid;
  place-items: center;
}

.og-card-icon svg {
  width: 18px;
  height: 18px;
}

.og-card-copy {
  font-size: 13px;
  line-height: 1.35;
  font-weight: 550;
}

.tone-explore .og-card-icon {
  color: var(--muted);
}

.tone-build .og-card-icon {
  color: var(--blue);
}

.tone-review .og-card-icon {
  color: var(--green);
}

.tone-fix .og-card-icon {
  color: var(--rose);
}

.composer-wrap {
  padding: 8px 24px 22px;
  display: flex;
  justify-content: center;
}

.composer-card {
  width: min(720px, 100%);
  border-radius: var(--r-xl);
  border: 1px solid var(--line);
  background: var(--bg);
  box-shadow: var(--shadow-sm);
  padding: 12px 14px 10px;
}

.composer-card:focus-within {
  border-color: color-mix(in srgb, var(--fg) 32%, transparent);
}

.composer-card textarea {
  width: 100%;
  min-height: 44px;
  max-height: 120px;
  resize: none;
  border: 0;
  background: transparent;
  outline: none;
  font-size: 14px;
  line-height: 1.45;
}

.composer-bar {
  display: flex;
  align-items: center;
  gap: 8px;
  margin-top: 8px;
  padding-top: 8px;
  border-top: 1px solid var(--line);
}

.chip,
.icon-btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  height: 32px;
  border: 0;
  border-radius: 999px;
  background: var(--elev);
  color: var(--muted);
  font-size: 12px;
  font-weight: 550;
}

.icon-btn {
  width: 32px;
  padding: 0;
}

.icon-btn svg,
.chip svg {
  width: 14px;
  height: 14px;
}

.chip {
  gap: 6px;
  padding: 0 10px;
}

.chip-model {
  margin-left: auto;
}

.send-btn {
  width: 36px;
  height: 36px;
  border: 0;
  border-radius: 999px;
  background: var(--fg);
  color: var(--bg);
  display: grid;
  place-items: center;
}

.send-btn svg {
  width: 16px;
  height: 16px;
}

.send-btn:hover {
  background: color-mix(in srgb, var(--fg) 88%, var(--bg));
}

.intro {
  max-width: var(--max);
  margin: 0 auto;
  padding: 36px 8px 12px;
  display: flex;
  flex-wrap: wrap;
  align-items: flex-start;
  justify-content: space-between;
  gap: 16px 24px;
}

.intro-copy {
  max-width: 640px;
}

.kicker {
  margin: 0 0 8px;
  color: var(--muted);
  font-size: 12px;
  font-weight: 650;
  letter-spacing: 0.06em;
}

.intro h2,
.section h2 {
  margin: 0;
  font-size: clamp(26px, 4vw, 36px);
  font-weight: 600;
  letter-spacing: -0.045em;
  line-height: 1.15;
}

.lead {
  margin: 10px 0 0;
  color: var(--muted);
  font-size: 15px;
  max-width: 58ch;
}

.intro-actions {
  display: flex;
  flex-wrap: wrap;
  gap: 10px;
  padding-top: 6px;
}

.section {
  max-width: var(--max);
  margin: 0 auto;
  padding: 56px 20px;
  scroll-margin-top: 72px;
}

.section-head {
  max-width: 640px;
  margin-bottom: 28px;
}

.feature-grid {
  display: grid;
  grid-template-columns: repeat(3, minmax(0, 1fr));
  gap: 12px;
}

.feature-card {
  min-height: 168px;
  padding: 20px;
  border-radius: var(--r-lg);
  border: 1px solid var(--line);
  background: var(--bg);
  box-shadow: var(--shadow-sm);
}

.feature-card h3 {
  margin: 18px 0 8px;
  font-size: 16px;
  font-weight: 620;
  letter-spacing: -0.03em;
}

.feature-card p {
  margin: 0;
  color: var(--muted);
  font-size: 13.5px;
  line-height: 1.55;
}

.feature-icon {
  width: 32px;
  height: 32px;
  display: grid;
  place-items: center;
  border-radius: 10px;
  background: var(--elev);
  color: var(--fg);
}

.feature-icon svg {
  width: 18px;
  height: 18px;
}

.steps {
  display: grid;
  grid-template-columns: repeat(3, minmax(0, 1fr));
  gap: 12px;
  counter-reset: step;
}

.step {
  padding: 22px;
  border-radius: var(--r-lg);
  background: var(--bg);
  border: 1px solid var(--line);
  box-shadow: var(--shadow-sm);
}

.step::before {
  counter-increment: step;
  content: counter(step);
  display: grid;
  place-items: center;
  width: 28px;
  height: 28px;
  margin-bottom: 14px;
  border-radius: 999px;
  background: var(--fg);
  color: var(--bg);
  font-size: 12px;
  font-weight: 700;
}

.step h3 {
  margin: 0 0 8px;
  font-size: 16px;
  font-weight: 620;
}

.step p {
  margin: 0;
  color: var(--muted);
  font-size: 13.5px;
}

.dl-grid {
  display: grid;
  grid-template-columns: repeat(2, minmax(0, 1fr));
  gap: 12px;
}

.dl-card {
  display: flex;
  flex-direction: column;
  gap: 8px;
  padding: 20px;
  border-radius: var(--r-lg);
  background: var(--bg);
  border: 1px solid var(--line);
  box-shadow: var(--shadow-sm);
  color: inherit;
  min-height: 132px;
}

.dl-card:hover {
  transform: translateY(-2px);
  background: color-mix(in srgb, var(--fg) 4%, var(--bg));
}

.dl-card strong {
  font-size: 16px;
  font-weight: 620;
}

.dl-card span {
  color: var(--muted);
  font-size: 13px;
}

.dl-card em {
  margin-top: auto;
  font-style: normal;
  font-size: 12px;
  font-weight: 620;
  color: var(--fg);
  overflow-wrap: anywhere;
}

.dl-more {
  margin: 14px 2px 0;
  font-size: 13px;
  font-weight: 550;
}

.dl-more a {
  color: var(--fg);
  border-bottom: 1px solid var(--line);
}

.dl-more a:hover {
  border-bottom-color: var(--fg);
}

.cli-box {
  margin-top: 16px;
  padding: 20px;
  border-radius: var(--r-lg);
  background: var(--bg);
  border: 1px solid var(--line);
}

.cli-box h3 {
  margin: 0 0 6px;
  font-size: 16px;
}

.cli-box p {
  margin: 0 0 14px;
  color: var(--muted);
  font-size: 13.5px;
}

.cmd {
  display: flex;
  align-items: center;
  gap: 10px;
  margin: 8px 0;
  padding: 10px 12px;
  border-radius: 10px;
  background: var(--elev);
  font-family: var(--mono);
  font-size: 12.5px;
  overflow: auto;
}

.cmd code {
  flex: 1;
  min-width: 0;
}

.cmd button {
  flex-shrink: 0;
  height: 28px;
  padding: 0 10px;
  border: 0;
  border-radius: 8px;
  background: var(--fg);
  color: var(--bg);
  font-family: var(--font);
  font-size: 12px;
  font-weight: 600;
}

.faq-list {
  display: grid;
  gap: 10px;
}

.faq-list details {
  border-radius: var(--r-lg);
  background: var(--bg);
  border: 1px solid var(--line);
  padding: 4px 18px;
}

.faq-list summary {
  cursor: pointer;
  list-style: none;
  padding: 14px 0;
  font-weight: 600;
  letter-spacing: -0.02em;
}

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

.faq-list details p {
  margin: 0 0 16px;
  color: var(--muted);
  font-size: 14px;
}

.site-footer {
  max-width: var(--max);
  margin: 0 auto;
  padding: 28px 20px 48px;
  display: flex;
  flex-wrap: wrap;
  gap: 10px 24px;
  align-items: center;
  color: var(--muted);
  font-size: 12.5px;
  border-top: 1px solid var(--line);
}

.site-footer a {
  color: var(--fg);
  font-weight: 550;
}

.hidden {
  display: none !important;
}

.visually-hidden {
  position: absolute;
  width: 1px;
  height: 1px;
  padding: 0;
  margin: -1px;
  overflow: hidden;
  clip: rect(0, 0, 0, 0);
  white-space: nowrap;
  border: 0;
}

.icon-moon {
  display: none;
}

html[data-theme='dark'] .icon-sun {
  display: none;
}

html[data-theme='dark'] .icon-moon {
  display: block;
}

@media (max-width: 960px) {
  .og-shell {
    grid-template-columns: 1fr;
    min-height: 0;
  }

  .og-rail {
    display: none;
  }

  .feature-grid,
  .steps {
    grid-template-columns: 1fr 1fr;
  }
}

@media (max-width: 720px) {
  .site-nav .nav-links,
  .site-nav .nav-tools .btn,
  .site-nav .nav-tools .theme-btn,
  .site-nav .lang-switch {
    display: none;
  }

  .site-nav .lang-compact,
  .site-nav .menu-btn {
    display: inline-flex;
    flex-shrink: 0;
  }

  .site-nav {
    padding: 0 12px;
    gap: 8px;
  }

  .og-win {
    display: none;
  }

  .og-home-mark {
    width: 72%;
    max-width: 220px;
  }

  .og-home-hint {
    padding: 0 20px;
    font-size: 12px;
  }

  .mobile-nav.open {
    display: flex;
    flex-direction: column;
    gap: 4px;
    padding: 12px 16px 16px;
    background: var(--bg);
    border-bottom: 1px solid var(--line);
  }

  .mobile-nav a,
  .mobile-nav .theme-btn {
    padding: 10px 12px;
    border-radius: 10px;
    font-weight: 550;
  }

  .mobile-nav .theme-btn {
    width: 100%;
    height: 40px;
    justify-content: flex-start;
    gap: 8px;
    border: 0;
    background: transparent;
  }

  .hero {
    padding: 16px 12px 0;
  }

  .og-window {
    border-radius: 14px;
  }

  .og-home {
    padding: 28px 16px 8px;
  }

  .og-cards,
  .feature-grid,
  .steps,
  .dl-grid {
    grid-template-columns: 1fr;
  }

  .og-card {
    min-height: 88px;
    flex-direction: row;
    align-items: center;
    gap: 12px;
  }

  .composer-wrap {
    padding: 8px 12px 16px;
  }

  .chip-model {
    display: none;
  }

  .send-btn {
    margin-left: auto;
  }

  .section {
    padding: 40px 16px;
  }

  .intro {
    padding: 28px 4px 8px;
  }
}