/* AI Chat — site styles.
   Editorial / technical layout: full-bleed, left-aligned, oversized type,
   monospace for labels and numbers, hairlines instead of card stacks.
   Two themes via [data-theme] on <html>; dark is the default. */

:root {
  --bg: #07090c;
  --bg-soft: #0b0e13;
  --fg: #f3f6fa;
  --fg-dim: #b6c1ce;
  --muted: #78838f;
  --accent: #7cc3ff;
  --accent-soft: rgba(124, 195, 255, 0.1);
  --line: rgba(255, 255, 255, 0.1);
  --line-soft: rgba(255, 255, 255, 0.055);
  --grid: rgba(255, 255, 255, 0.022);
  --btn-text: #04131f;
  --btn-1: #8cd6ff;
  --btn-2: #2b9fe8;
  --btn-shadow: rgba(0, 120, 212, 0.22);
  --code-bg: rgba(255, 255, 255, 0.07);
  --header-bg: rgba(7, 9, 12, 0.82);
  --card-bg: rgba(255, 255, 255, 0.028);
  --card-bg-hover: rgba(255, 255, 255, 0.05);
  --pad: clamp(20px, 4.2vw, 64px);
  --ease: cubic-bezier(0.4, 0, 0.2, 1);
  --mono: ui-monospace, "Cascadia Code", "Consolas", "SF Mono", monospace;
}

html[data-theme="light"] {
  --bg: #f6f7f9;
  --bg-soft: #ffffff;
  --fg: #0b1118;
  --fg-dim: #3c4653;
  --muted: #626c79;
  --accent: #0a66b3;
  --accent-soft: rgba(10, 102, 179, 0.08);
  --line: rgba(11, 17, 24, 0.13);
  --line-soft: rgba(11, 17, 24, 0.07);
  --grid: rgba(11, 17, 24, 0.035);
  --btn-text: #ffffff;
  --btn-1: #1f9be0;
  --btn-2: #0a66b3;
  --btn-shadow: rgba(10, 102, 179, 0.2);
  --code-bg: rgba(11, 17, 24, 0.06);
  --header-bg: rgba(246, 247, 249, 0.86);
  --card-bg: #fafbfd;
  --card-bg-hover: #ffffff;
}

* {
  box-sizing: border-box;
}

html {
  scroll-behavior: smooth;
  /* keep anchor targets clear of the sticky header */
  scroll-padding-top: 84px;
}

body {
  margin: 0;
  padding: clamp(10px, 1.4vw, 22px);
  background: var(--bg);
  color: var(--fg);
  font-family: "Segoe UI Variable Display", "Segoe UI", "Microsoft YaHei UI",
    "Microsoft YaHei", system-ui, -apple-system, sans-serif;
  font-size: 15px;
  line-height: 1.7;
  -webkit-font-smoothing: antialiased;
  overflow-x: hidden;
  transition: background 0.5s var(--ease), color 0.5s var(--ease);
}

/* One big rounded panel holds the whole page: gives the content an edge
   without shrinking it to a narrow column. */
.shell {
  position: relative;
  max-width: 1560px;
  margin: 0 auto;
  border: 1px solid var(--line-soft);
  border-radius: 24px;
  background: var(--bg-soft);
  overflow: clip;
  transition: background 0.5s var(--ease), border-color 0.5s var(--ease);
}

/* fine grid, fading out downwards — the only "texture" on the page */
.grid-bg {
  position: absolute;
  inset: 0;
  z-index: 0;
  pointer-events: none;
  border-radius: inherit;
  background-image: linear-gradient(var(--grid) 1px, transparent 1px),
    linear-gradient(90deg, var(--grid) 1px, transparent 1px);
  background-size: 76px 76px;
  mask-image: radial-gradient(120% 70% at 50% 0%, #000 0%, transparent 72%);
  -webkit-mask-image: radial-gradient(120% 70% at 50% 0%, #000 0%, transparent 72%);
  transition: background-image 0.5s var(--ease);
}

.mono {
  font-family: var(--mono);
  font-size: 12px;
  letter-spacing: 0.06em;
}

/* ---------------------------------------------------------------- header */
.site-header {
  position: sticky;
  top: 0;
  z-index: 20;
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 20px;
  padding: 16px var(--pad);
  background: var(--header-bg);
  backdrop-filter: blur(14px);
  border-bottom: 1px solid var(--line-soft);
  transition: background 0.5s var(--ease), border-color 0.5s var(--ease);
}

.brand {
  display: inline-flex;
  align-items: center;
  gap: 10px;
  color: var(--fg);
  text-decoration: none;
  font-weight: 600;
  font-size: 14.5px;
}
.brand img {
  border-radius: 7px;
}

.header-tools {
  display: flex;
  align-items: center;
  gap: clamp(14px, 1.8vw, 28px);
}

.nav {
  display: flex;
  gap: clamp(14px, 1.8vw, 28px);
}
.nav a {
  color: var(--muted);
  text-decoration: none;
  font-size: 13.5px;
  transition: color 0.4s var(--ease);
}
.nav a:hover {
  color: var(--fg);
}

.theme-toggle {
  display: grid;
  place-items: center;
  width: 34px;
  height: 34px;
  border-radius: 9px;
  border: 1px solid var(--line-soft);
  background: transparent;
  color: var(--muted);
  cursor: pointer;
  transition: color 0.4s var(--ease), border-color 0.4s var(--ease),
    background 0.4s var(--ease);
}
.theme-toggle:hover {
  color: var(--fg);
  border-color: var(--line);
  background: var(--accent-soft);
}
.theme-toggle .icon {
  width: 17px;
  height: 17px;
}
.theme-toggle .i-moon {
  display: none;
}
html[data-theme="light"] .theme-toggle .i-sun {
  display: none;
}
html[data-theme="light"] .theme-toggle .i-moon {
  display: block;
}

/* ------------------------------------------------------------------ main */
main {
  position: relative;
  z-index: 1;
  padding: 0;
}

.section {
  padding: clamp(56px, 9vh, 120px) var(--pad);
}

.section-head {
  margin-bottom: clamp(28px, 4vh, 44px);
}
.section-head h2 {
  margin: 10px 0 0;
  font-size: clamp(24px, 3.1vw, 38px);
  font-weight: 650;
  letter-spacing: -0.9px;
  line-height: 1.25;
}

.tag {
  color: var(--accent);
  opacity: 0.9;
}

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

/* ------------------------------------------------------------------ hero */
.hero {
  display: grid;
  grid-template-columns: minmax(0, 1.6fr) minmax(260px, 0.85fr);
  gap: clamp(28px, 5vw, 80px);
  align-items: end;
  padding: clamp(56px, 10vh, 120px) var(--pad) clamp(44px, 7vh, 88px);
}

.hero h1 {
  margin: 18px 0 22px;
  font-size: clamp(38px, 6.2vw, 82px);
  line-height: 1.03;
  font-weight: 700;
  letter-spacing: -2.6px;
}
.hero h1 span {
  display: block;
}
.line-1 {
  color: var(--fg);
}
/* second line recedes — creates hierarchy without extra colour */
.line-2 {
  color: var(--muted);
}

.lead {
  margin: 0 0 30px;
  color: var(--fg-dim);
  font-size: clamp(14.5px, 1.05vw, 16px);
  line-height: 1.75;
}

.actions {
  display: flex;
  align-items: center;
  flex-wrap: wrap;
  gap: 22px;
}

.btn {
  display: inline-flex;
  align-items: center;
  gap: 8px;
  padding: 12px 22px;
  border-radius: 10px;
  border: 1px solid transparent;
  font-family: inherit;
  font-size: 14.5px;
  font-weight: 600;
  text-decoration: none;
  cursor: pointer;
  transition: transform 0.45s var(--ease), box-shadow 0.55s var(--ease),
    background 0.45s var(--ease), border-color 0.45s var(--ease),
    color 0.45s var(--ease);
}
.btn.primary {
  background: linear-gradient(135deg, var(--btn-1), var(--btn-2));
  color: var(--btn-text);
  box-shadow: 0 8px 22px var(--btn-shadow);
}
.btn.primary:hover {
  transform: translateY(-1.5px);
  box-shadow: 0 14px 32px var(--btn-shadow);
}
.btn.link {
  padding: 12px 0;
  color: var(--fg-dim);
  border-bottom: 1px solid transparent;
}
.btn.link:hover {
  color: var(--fg);
  border-bottom-color: var(--line);
}

/* Icons inherit the text colour of whatever they sit in — a fixed accent
   colour used to disappear against the bright primary button. */
.icon {
  width: 17px;
  height: 17px;
  fill: none;
  stroke: currentColor;
  stroke-width: 1.7;
  stroke-linecap: round;
  stroke-linejoin: round;
  flex: none;
}

/* ------------------------------------------------------------- spec board */
.spec {
  align-self: end;
  border: 1px solid var(--line-soft);
  border-radius: 16px;
  background: var(--card-bg);
  padding: 16px 18px;
  transition: border-color 0.5s var(--ease), background 0.5s var(--ease);
}
.spec:hover {
  border-color: var(--line);
  background: var(--card-bg-hover);
}
.spec-title {
  margin: 0 0 12px;
  color: var(--muted);
}
.spec dl {
  margin: 0;
}
.spec dl > div {
  display: flex;
  align-items: baseline;
  justify-content: space-between;
  gap: 16px;
  padding: 9px 0;
  border-bottom: 1px solid var(--line-soft);
}
.spec dl > div:last-child {
  border-bottom: 0;
  padding-bottom: 2px;
}
.spec dt {
  color: var(--muted);
  font-size: 12.5px;
}
.spec dd {
  margin: 0;
  font-size: 13px;
  font-weight: 500;
  color: var(--fg);
  text-align: right;
}
.spec dd.mono {
  font-family: var(--mono);
  font-size: 12.5px;
  letter-spacing: 0.02em;
}

/* --------------------------------------------------------------- features */
.feat-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(320px, 1fr));
  gap: 14px;
}

.feat {
  padding: 24px;
  border: 1px solid var(--line-soft);
  border-radius: 16px;
  background: var(--card-bg);
  transition: border-color 0.5s var(--ease), background 0.5s var(--ease),
    transform 0.5s var(--ease);
}
.feat:hover {
  border-color: var(--line);
  background: var(--card-bg-hover);
  transform: translateY(-2px);
}
.feat-no {
  display: block;
  color: var(--accent);
  opacity: 0.75;
  margin-bottom: 8px;
}
.feat h3 {
  margin: 0 0 6px;
  font-size: 16.5px;
  font-weight: 620;
  letter-spacing: -0.1px;
}
.feat p {
  margin: 0;
  color: var(--muted);
  font-size: 13.8px;
  line-height: 1.72;
}

/* ------------------------------------------------------------------ steps */
.steps {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(260px, 1fr));
  gap: 14px;
  list-style: none;
  margin: 0;
  padding: 0;
}
.steps li {
  padding: 24px;
  border: 1px solid var(--line-soft);
  border-radius: 16px;
  background: var(--card-bg);
  transition: border-color 0.5s var(--ease), background 0.5s var(--ease),
    transform 0.5s var(--ease);
}
.steps li:hover {
  border-color: var(--line);
  background: var(--card-bg-hover);
  transform: translateY(-2px);
}
.step-no {
  display: block;
  font-size: 26px;
  color: var(--muted);
  opacity: 0.55;
  letter-spacing: -0.02em;
  margin-bottom: 10px;
}
.steps h3 {
  margin: 0 0 7px;
  font-size: 17px;
  font-weight: 620;
}
.steps p {
  margin: 0;
  color: var(--muted);
  font-size: 13.8px;
}

/* -------------------------------------------------------------- spec table */
.panel {
  border: 1px solid var(--line-soft);
  border-radius: 16px;
  background: var(--card-bg);
  overflow: hidden;
  transition: border-color 0.5s var(--ease), background 0.5s var(--ease);
}
.panel:hover {
  border-color: var(--line);
  background: var(--card-bg-hover);
}

.spec-table {
  width: 100%;
  border-collapse: collapse;
}
.spec-table tr {
  border-top: 1px solid var(--line-soft);
}
.spec-table tr:first-child {
  border-top: 0;
}
.spec-table th {
  width: 132px;
  padding: 16px 20px 16px 20px;
  text-align: left;
  vertical-align: top;
  font-family: var(--mono);
  font-size: 12px;
  font-weight: 500;
  letter-spacing: 0.06em;
  color: var(--muted);
}
.spec-table td {
  padding: 16px 20px 16px 0;
  font-size: 14px;
  color: var(--fg-dim);
  line-height: 1.7;
}

/* --------------------------------------------------------------- download */
.download-band {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: clamp(20px, 3vw, 40px);
  flex-wrap: wrap;
  padding: clamp(20px, 2.4vw, 26px) clamp(22px, 3vw, 32px);
  border: 1px solid var(--line-soft);
  border-radius: 20px;
  background: var(--card-bg);
  transition: border-color 0.5s var(--ease), background 0.5s var(--ease);
}
.download-band:hover {
  border-color: var(--line);
  background: var(--card-bg-hover);
}
.facts {
  display: flex;
  gap: clamp(22px, 2.6vw, 40px);
  margin: 0;
}
.facts > div {
  display: flex;
  flex-direction: column;
  gap: 2px;
}
.facts dt {
  font-size: 11.5px;
  color: var(--muted);
  letter-spacing: 0.05em;
}
.facts dd {
  margin: 0;
  font-size: 13px;
  font-weight: 500;
}

.hint {
  margin: 18px 0 0;
  color: var(--muted);
  font-size: 12.5px;
  line-height: 1.8;
}

/* ------------------------------------------------------------------ faq */
.faq {
  display: grid;
  gap: 10px;
}
.faq-item {
  border: 1px solid var(--line-soft);
  border-radius: 14px;
  background: var(--card-bg);
  transition: border-color 0.5s var(--ease), background 0.5s var(--ease);
}
.faq-item:hover {
  border-color: var(--line);
  background: var(--card-bg-hover);
}
.faq-q {
  width: 100%;
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 16px;
  padding: 17px 20px;
  border: 0;
  background: none;
  color: var(--fg);
  font-family: inherit;
  font-size: 14.8px;
  font-weight: 600;
  text-align: left;
  cursor: pointer;
}
.chev {
  color: var(--muted);
  transition: transform 0.5s var(--ease), color 0.5s var(--ease);
}
.faq-item.open .chev {
  transform: rotate(180deg);
  color: var(--accent);
}
/* 0fr -> 1fr animates the real height without measuring anything */
.faq-a {
  display: grid;
  grid-template-rows: 0fr;
  opacity: 0;
  transition: grid-template-rows 0.5s var(--ease), opacity 0.4s var(--ease);
}
.faq-item.open .faq-a {
  grid-template-rows: 1fr;
  opacity: 1;
}
.faq-inner {
  overflow: hidden;
}
.faq-inner p {
  margin: 0;
  padding: 0 20px 18px;
  color: var(--muted);
  font-size: 13.9px;
  line-height: 1.78;
}
code {
  padding: 1px 5px;
  border-radius: 4px;
  background: var(--code-bg);
  font-family: var(--mono);
  font-size: 12px;
  color: var(--fg-dim);
}

/* ---------------------------------------------------------------- footer */
.site-footer {
  position: relative;
  z-index: 1;
  padding: 18px var(--pad) 22px;
  text-align: center;
}
.site-footer p {
  margin: 0;
  color: var(--muted);
  font-size: 12.5px;
  letter-spacing: 0.02em;
}

/* --------------------------------------------------------------- reveal */
.reveal {
  opacity: 0;
  transform: translateY(14px);
  transition: opacity 0.9s var(--ease), transform 0.9s var(--ease);
}
.reveal.visible {
  opacity: 1;
  transform: none;
}

@media (prefers-reduced-motion: reduce) {
  html {
    scroll-behavior: auto;
  }
  .reveal {
    opacity: 1;
    transform: none;
    transition: none;
  }
  .faq-a {
    transition: none;
  }
}

/* ------------------------------------------------------------ responsive */
@media (max-width: 900px) {
  .hero {
    grid-template-columns: 1fr;
    align-items: start;
    gap: 34px;
    padding-top: 56px;
  }
  .spec {
    max-width: none;
  }
  .nav {
    display: none;
  }
  .hero h1 {
    letter-spacing: -1.6px;
  }  .facts {
    gap: 20px;
  }
  .spec-table th {
    width: 96px;
    padding-right: 12px;
  }
}