/* ============================================================
   rfc9842-reply — site styles
   jixoai design language: one brand hue, OKLCH, mono-first,
   pure-black background. No external fonts, no images.
   ============================================================ */

:root {
  /* The only per-project variable: brand hue (OKLCH degrees).
     Cyan reads as "wire / tunnel / data". */
  --brand-hue: 200;

  --bg: oklch(0 0 0);
  --fg: oklch(1 0 0);
  --fg-muted: oklch(0.72 0 0);
  --fg-dim: oklch(0.55 0 0);

  --panel: oklch(0.16 0 0);
  --panel-2: oklch(0.21 0 0);

  --primary: oklch(0.7044 0.1872 calc(var(--brand-hue) - 4));
  --primary-dim: oklch(0.55 0.14 calc(var(--brand-hue) - 4));

  --line: oklch(1 0 0 / 0.10);
  --line-strong: oklch(1 0 0 / 0.20);

  --ok: oklch(0.7395 0.2268 142.85);
  --warn: oklch(0.78 0.16 85);

  --mono: ui-monospace, SFMono-Regular, "SF Mono", Menlo, Consolas,
    "Liberation Mono", "Courier New", monospace;

  --maxw: 1080px;
  --pad: clamp(1.25rem, 4vw, 2.5rem);
}

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

html {
  color-scheme: dark;
  -webkit-text-size-adjust: 100%;
}

body {
  margin: 0;
  background: var(--bg);
  color: var(--fg);
  font-family: var(--mono);
  font-size: 15px;
  line-height: 1.65;
  font-variant-ligatures: none;
  -webkit-font-smoothing: antialiased;
  text-rendering: optimizeLegibility;
}

::selection {
  background: var(--primary);
  color: #000;
}

a {
  color: var(--primary);
  text-decoration: none;
  transition: color 120ms ease, opacity 120ms ease;
}

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

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

code,
kbd {
  font-family: var(--mono);
}

/* ---------- layout ---------- */

.wrap {
  width: 100%;
  max-width: var(--maxw);
  margin-inline: auto;
  padding-inline: var(--pad);
}

section {
  padding-block: clamp(3.5rem, 8vw, 6.5rem);
  border-top: 1px solid var(--line);
  /* 锚点跳转时不要被 sticky header 盖住标题 */
  scroll-margin-top: 72px;
}

section:first-of-type {
  border-top: 0;
}

/* ---------- header ---------- */

.site-header {
  position: sticky;
  top: 0;
  z-index: 50;
  background: color-mix(in oklab, var(--bg) 82%, transparent);
  backdrop-filter: blur(12px) contrast(0.8) brightness(1.2);
  border-bottom: 1px solid var(--line);
}

.site-header .wrap {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 1rem;
  min-height: 56px;
}

.brand {
  display: inline-flex;
  align-items: center;
  gap: 0.55rem;
  color: var(--fg);
  font-size: 13px;
  letter-spacing: 0.02em;
  white-space: nowrap;
}

.brand:hover {
  color: var(--fg);
}

.brand-mark {
  width: 9px;
  height: 9px;
  background: var(--primary);
  border-radius: 1px;
  box-shadow: 0 0 12px var(--primary);
  flex: none;
}

.brand-name {
  font-weight: 600;
}

.brand-tag {
  color: var(--fg-dim);
  font-size: 11px;
  padding-left: 0.55rem;
  border-left: 1px solid var(--line);
}

.nav {
  display: flex;
  align-items: center;
  gap: 1.25rem;
  font-size: 12px;
}

.nav a {
  color: var(--fg-muted);
}

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

/* ---------- hero ---------- */

.hero {
  padding-block: clamp(3.5rem, 9vw, 7rem) clamp(3rem, 6vw, 5rem);
  position: relative;
  overflow: hidden;
}

.hero::before {
  content: "";
  position: absolute;
  inset: -40% 50% auto -20%;
  height: 70%;
  background: radial-gradient(
    ellipse at center,
    color-mix(in oklab, var(--primary) 14%, transparent),
    transparent 65%
  );
  pointer-events: none;
}

.hero > .wrap {
  position: relative;
}

.eyebrow {
  display: inline-flex;
  align-items: center;
  gap: 0.5rem;
  font-size: 11px;
  letter-spacing: 0.14em;
  text-transform: uppercase;
  color: var(--fg-dim);
  margin: 0 0 1.5rem;
}

.eyebrow::before {
  content: "";
  width: 22px;
  height: 1px;
  background: var(--primary);
}

h1 {
  margin: 0 0 1.25rem;
  font-size: clamp(2rem, 5.6vw, 3.4rem);
  line-height: 1.1;
  letter-spacing: -0.035em;
  font-weight: 650;
  max-width: 20ch;
}

h1 em {
  font-style: normal;
  color: var(--primary);
}

.lede {
  margin: 0;
  max-width: 62ch;
  color: var(--fg-muted);
  font-size: clamp(0.95rem, 1.6vw, 1.06rem);
}

.lede strong {
  color: var(--fg);
  font-weight: 600;
}

/* ---------- hero stats ---------- */

.stats {
  display: grid;
  grid-template-columns: repeat(3, minmax(0, 1fr));
  gap: 1px;
  margin-top: clamp(2.5rem, 5vw, 3.5rem);
  border: 1px solid var(--line);
  background: var(--line);
}

.stat {
  background: var(--bg);
  padding: clamp(1rem, 2.4vw, 1.5rem);
  min-width: 0;
}

.stat-label {
  display: block;
  font-size: 10.5px;
  letter-spacing: 0.11em;
  text-transform: uppercase;
  color: var(--fg-dim);
  margin-bottom: 0.7rem;
}

.stat-value {
  display: block;
  font-size: clamp(1.5rem, 3.6vw, 2.35rem);
  font-weight: 600;
  letter-spacing: -0.03em;
  line-height: 1.1;
  color: var(--primary);
  word-break: break-word;
}

.stat-value .unit {
  font-size: 0.5em;
  color: var(--fg-muted);
  letter-spacing: 0;
  font-weight: 500;
}

.stat-note {
  display: block;
  margin-top: 0.55rem;
  font-size: 11.5px;
  color: var(--fg-dim);
  line-height: 1.5;
}

/* ---------- hero actions ---------- */

.actions {
  display: flex;
  flex-wrap: wrap;
  gap: 0.75rem;
  margin-top: 2rem;
}

.btn {
  display: inline-flex;
  align-items: center;
  gap: 0.5rem;
  padding: 0.68rem 1.15rem;
  font-family: var(--mono);
  font-size: 12.5px;
  border: 1px solid var(--line-strong);
  background: transparent;
  color: var(--fg);
  cursor: pointer;
  transition: transform 120ms ease, background 120ms ease,
    border-color 120ms ease, color 120ms ease;
  border-radius: 3px;
}

.btn:hover {
  transform: translateY(-1px);
  border-color: var(--fg);
  color: var(--fg);
}

.btn:active {
  transform: translateY(0);
}

.btn-primary {
  background: var(--primary);
  border-color: var(--primary);
  color: #000;
  font-weight: 600;
}

.btn-primary:hover {
  background: var(--fg);
  border-color: var(--fg);
  color: #000;
}

.btn .arrow {
  color: currentColor;
  opacity: 0.7;
}

/* ---------- section headings ---------- */

.sec-head {
  margin-bottom: clamp(2rem, 4vw, 3rem);
}

.sec-num {
  display: block;
  font-size: 11px;
  letter-spacing: 0.14em;
  color: var(--primary);
  margin-bottom: 0.75rem;
}

h2 {
  margin: 0 0 0.85rem;
  font-size: clamp(1.35rem, 3vw, 1.85rem);
  line-height: 1.2;
  letter-spacing: -0.02em;
  font-weight: 620;
}

.sec-sub {
  margin: 0;
  max-width: 66ch;
  color: var(--fg-muted);
  font-size: 0.94rem;
}

/* ---------- prose ---------- */

.prose p {
  margin: 0 0 1rem;
  max-width: 68ch;
  color: var(--fg-muted);
}

.prose p:last-child {
  margin-bottom: 0;
}

.prose strong {
  color: var(--fg);
  font-weight: 600;
}

.prose code,
.inline-code {
  font-size: 0.88em;
  padding: 0.1em 0.36em;
  background: var(--panel-2);
  border: 1px solid var(--line);
  border-radius: 3px;
  color: var(--fg);
  white-space: nowrap;
}

/* ---------- problem grid ---------- */

.pain {
  display: grid;
  grid-template-columns: 1.1fr 0.9fr;
  gap: clamp(1.5rem, 4vw, 3rem);
  align-items: start;
}

.kv {
  border: 1px solid var(--line);
  border-radius: 3px;
  overflow: hidden;
}

.kv-row {
  display: flex;
  justify-content: space-between;
  gap: 1rem;
  padding: 0.62rem 0.9rem;
  border-top: 1px solid var(--line);
  font-size: 12.5px;
}

.kv-row:first-child {
  border-top: 0;
  background: var(--panel);
}

.kv-row span:first-child {
  color: var(--fg-muted);
}

.kv-row span:last-child {
  color: var(--fg);
  font-weight: 600;
  white-space: nowrap;
}

.kv-row.hl span:last-child {
  color: var(--primary);
}

/* ---------- diagram ---------- */

.diagram {
  border: 1px solid var(--line);
  border-radius: 4px;
  background:
    linear-gradient(var(--line) 1px, transparent 1px) 0 0 / 100% 28px,
    linear-gradient(90deg, var(--line) 1px, transparent 1px) 0 0 / 28px 100%,
    var(--bg);
  padding: clamp(1rem, 3vw, 1.75rem);
  overflow-x: auto;
}

.diagram-grid {
  display: grid;
  grid-template-columns: minmax(0, 1fr) minmax(96px, 0.42fr) minmax(0, 1fr);
  gap: 0;
  align-items: stretch;
  min-width: 620px;
}

.node {
  border: 1px solid var(--line-strong);
  border-radius: 3px;
  background: color-mix(in oklab, var(--panel) 88%, transparent);
  padding: 0.9rem 1rem 1rem;
}

.node-head {
  display: flex;
  align-items: baseline;
  justify-content: space-between;
  gap: 0.5rem;
  padding-bottom: 0.6rem;
  margin-bottom: 0.75rem;
  border-bottom: 1px solid var(--line);
}

.node-name {
  font-size: 12px;
  font-weight: 600;
  color: var(--fg);
  letter-spacing: -0.01em;
}

.node-sub {
  font-size: 10px;
  color: var(--fg-dim);
  letter-spacing: 0.06em;
  text-transform: uppercase;
}

.steps {
  list-style: none;
  margin: 0;
  padding: 0;
  display: grid;
  gap: 0.55rem;
  font-size: 11.5px;
  line-height: 1.45;
  color: var(--fg-muted);
}

.steps li {
  display: grid;
  grid-template-columns: 1.35rem 1fr;
  gap: 0.5rem;
  align-items: start;
}

.step-n {
  font-size: 10px;
  color: var(--primary);
  border: 1px solid color-mix(in oklab, var(--primary) 45%, transparent);
  border-radius: 2px;
  text-align: center;
  line-height: 1.35rem;
  height: 1.35rem;
}

.steps b {
  color: var(--fg);
  font-weight: 600;
}

/* tunnel link in the middle */
.link-col {
  display: flex;
  flex-direction: column;
  align-items: center;
  justify-content: center;
  gap: 0.5rem;
  padding-inline: 0.4rem;
}

.link-label {
  font-size: 9.5px;
  letter-spacing: 0.1em;
  text-transform: uppercase;
  color: var(--fg-dim);
  text-align: center;
  white-space: nowrap;
}

.wire {
  position: relative;
  width: 100%;
  height: 2px;
  background: color-mix(in oklab, var(--primary) 22%, transparent);
  overflow: hidden;
}

.wire::after {
  content: "";
  position: absolute;
  inset: 0;
  width: 38%;
  background: linear-gradient(
    90deg,
    transparent,
    var(--primary),
    transparent
  );
  animation: flow 2.4s linear infinite;
}

.wire-arrow {
  color: var(--primary);
  font-size: 13px;
  line-height: 1;
}

@keyframes flow {
  0% {
    transform: translateX(-120%);
  }
  100% {
    transform: translateX(320%);
  }
}

.wire-meta {
  font-size: 10px;
  color: var(--primary);
  white-space: nowrap;
}

.diagram-caption {
  margin: 1rem 0 0;
  font-size: 11px;
  color: var(--fg-dim);
}

/* ---------- code ---------- */

.code {
  border: 1px solid var(--line);
  border-radius: 4px;
  overflow: hidden;
  background: var(--panel);
  margin-bottom: 1.25rem;
}

.code-head {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 1rem;
  padding: 0.5rem 0.85rem;
  border-bottom: 1px solid var(--line);
  background: var(--panel-2);
  font-size: 10.5px;
  letter-spacing: 0.08em;
  text-transform: uppercase;
  color: var(--fg-dim);
}

.code pre {
  margin: 0;
  padding: 0.9rem 1rem 1.05rem;
  overflow-x: auto;
  font-size: 12.5px;
  line-height: 1.75;
  color: var(--fg-muted);
  tab-size: 2;
}

.code pre b {
  color: var(--fg);
  font-weight: 600;
}

.code pre i {
  font-style: normal;
  color: var(--primary);
}

.code pre u {
  text-decoration: none;
  color: var(--fg-dim);
}

.code-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(320px, 1fr));
  gap: 0 1.25rem;
}

/* ---------- tables ---------- */

.table-scroll {
  overflow-x: auto;
  border: 1px solid var(--line);
  border-radius: 4px;
}

table {
  width: 100%;
  border-collapse: collapse;
  font-size: 12.5px;
  min-width: 520px;
}

th,
td {
  padding: 0.5rem 0.75rem;
  text-align: left;
  border-top: 1px solid var(--line);
  white-space: nowrap;
}

thead th {
  border-top: 0;
  background: var(--panel);
  font-size: 10.5px;
  letter-spacing: 0.08em;
  text-transform: uppercase;
  color: var(--fg-dim);
  font-weight: 500;
  position: sticky;
  top: 0;
}

tbody td {
  color: var(--fg-muted);
}

td.num,
th.num {
  text-align: right;
  font-variant-numeric: tabular-nums;
}

tbody tr:hover td {
  background: color-mix(in oklab, var(--panel) 60%, transparent);
  color: var(--fg);
}

tr.total td {
  border-top: 1px solid var(--line-strong);
  background: var(--panel-2);
  color: var(--fg);
  font-weight: 600;
}

tr.total td.hl {
  color: var(--primary);
}

.tag {
  display: inline-block;
  font-size: 10px;
  padding: 0.1em 0.42em;
  border: 1px solid var(--line-strong);
  border-radius: 2px;
  color: var(--fg-dim);
  letter-spacing: 0.02em;
}

.tag-hi {
  border-color: color-mix(in oklab, var(--primary) 50%, transparent);
  color: var(--primary);
}

.footnote {
  margin: 0.85rem 0 0;
  font-size: 11.5px;
  color: var(--fg-dim);
  max-width: 70ch;
}

.footnote sup,
sup.fn {
  color: var(--primary);
}

/* ---------- comparison bars ---------- */

.bars {
  display: grid;
  gap: 0.7rem;
  margin-top: 1.75rem;
}

.bar-row {
  display: grid;
  grid-template-columns: 11rem 1fr 7.5rem;
  gap: 0.75rem;
  align-items: center;
  font-size: 11.5px;
}

.bar-name {
  color: var(--fg-muted);
  white-space: nowrap;
}

.bar-name b {
  color: var(--fg);
  font-weight: 600;
}

.bar-track {
  height: 10px;
  background: var(--panel);
  border: 1px solid var(--line);
  border-radius: 1px;
  overflow: hidden;
}

.bar-fill {
  height: 100%;
  background: var(--fg-dim);
}

.bar-row.best .bar-fill {
  background: var(--primary);
  box-shadow: 0 0 14px color-mix(in oklab, var(--primary) 60%, transparent);
}

.bar-val {
  text-align: right;
  color: var(--fg);
  font-variant-numeric: tabular-nums;
  white-space: nowrap;
}

.bar-row.best .bar-val {
  color: var(--primary);
  font-weight: 600;
}

/* ---------- decision cards ---------- */

.cards {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(260px, 1fr));
  gap: 1rem;
}

.card {
  border: 1px solid var(--line);
  border-radius: 4px;
  padding: 1.15rem 1.15rem 1.3rem;
  background: linear-gradient(180deg, var(--panel), transparent);
  transition: border-color 140ms ease, transform 140ms ease;
}

.card:hover {
  border-color: var(--line-strong);
  transform: translateY(-2px);
}

.card-n {
  display: block;
  font-size: 10px;
  letter-spacing: 0.14em;
  color: var(--primary);
  margin-bottom: 0.6rem;
}

.card h3 {
  margin: 0 0 0.6rem;
  font-size: 13.5px;
  line-height: 1.4;
  font-weight: 620;
  letter-spacing: -0.01em;
}

.card p {
  margin: 0;
  font-size: 12px;
  color: var(--fg-muted);
  line-height: 1.6;
}

.card .metric {
  display: block;
  margin-top: 0.85rem;
  padding-top: 0.7rem;
  border-top: 1px solid var(--line);
  font-size: 11px;
  color: var(--fg-dim);
}

.card .metric b {
  color: var(--primary);
  font-weight: 600;
}

/* ---------- limitation list ---------- */

.notes {
  list-style: none;
  margin: 0;
  padding: 0;
  display: grid;
  gap: 0;
  border: 1px solid var(--line);
  border-radius: 4px;
  overflow: hidden;
}

.notes li {
  display: grid;
  grid-template-columns: 2.2rem 1fr;
  gap: 0.5rem;
  padding: 0.75rem 0.95rem;
  border-top: 1px solid var(--line);
  font-size: 12px;
  color: var(--fg-muted);
  line-height: 1.6;
}

.notes li:first-child {
  border-top: 0;
}

.notes li b {
  color: var(--fg);
  font-weight: 600;
}

.notes .idx {
  color: var(--fg-dim);
  font-size: 10.5px;
}

/* ---------- spec grid ---------- */

.specs {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(220px, 1fr));
  gap: 1px;
  background: var(--line);
  border: 1px solid var(--line);
  border-radius: 4px;
  overflow: hidden;
}

.spec {
  background: var(--bg);
  padding: 0.9rem 1rem;
}

.spec-id {
  display: block;
  font-size: 12px;
  color: var(--primary);
  margin-bottom: 0.2rem;
}

.spec-name {
  display: block;
  font-size: 11.5px;
  color: var(--fg);
  margin-bottom: 0.35rem;
}

.spec-use {
  display: block;
  font-size: 11px;
  color: var(--fg-dim);
  line-height: 1.5;
}

/* ---------- footer ---------- */

.site-footer {
  border-top: 1px solid var(--line);
  padding-block: clamp(2.5rem, 5vw, 3.5rem) 2rem;
}

.foot-grid {
  display: flex;
  flex-wrap: wrap;
  gap: 1.5rem 2.5rem;
  justify-content: space-between;
  align-items: flex-start;
}

.foot-brand {
  font-size: 12px;
  color: var(--fg-muted);
  max-width: 34ch;
  line-height: 1.7;
}

.foot-brand .brand {
  margin-bottom: 0.7rem;
}

.foot-desc {
  display: block;
  line-height: 1.75;
}

.foot-desc + .foot-desc {
  margin-top: 0.35rem;
}

.foot-links {
  display: flex;
  flex-wrap: wrap;
  gap: 0.4rem 1.5rem;
  font-size: 12px;
}

.foot-links a {
  color: var(--fg-muted);
}

.foot-links a:hover {
  color: var(--primary);
}

.colophon {
  margin-top: 2.5rem;
  padding-top: 1.25rem;
  border-top: 1px solid var(--line);
  display: flex;
  flex-wrap: wrap;
  gap: 0.5rem 1.5rem;
  justify-content: space-between;
  font-size: 10.5px;
  color: var(--fg-dim);
  letter-spacing: 0.02em;
}

.wordmark {
  font-size: clamp(1.6rem, 7vw, 3.4rem);
  font-weight: 700;
  letter-spacing: -0.05em;
  color: transparent;
  -webkit-text-stroke: 1px var(--line-strong);
  line-height: 1;
  margin-top: 2rem;
  user-select: none;
}

/* ---------- responsive ---------- */

@media (max-width: 860px) {
  .pain {
    grid-template-columns: 1fr;
  }

  /* 手机上条形图改为「名称 · 条 · 数值」三段并排，不再换行 */
  .bar-row {
    grid-template-columns: minmax(0, 1fr) 3.6rem;
    grid-template-areas:
      "name val"
      "track track";
    row-gap: 0.35rem;
    align-items: center;
  }

  .bar-name {
    grid-area: name;
    font-size: 11.5px;
  }

  .bar-val {
    grid-area: val;
    text-align: right;
    font-size: 11.5px;
  }

  .bar-track {
    grid-area: track;
  }
}

@media (max-width: 720px) {
  .stats {
    grid-template-columns: 1fr;
  }

  section {
    padding-block: 3rem;
  }

  .nav {
    gap: 0.9rem;
  }

  .nav .nav-hide {
    display: none;
  }

  .brand-tag {
    display: none;
  }

  /* stack the diagram vertically on small screens */
  .diagram-grid {
    grid-template-columns: 1fr;
    min-width: 0;
    gap: 0.5rem;
  }

  .link-col {
    flex-direction: row;
    gap: 0.6rem;
    padding: 0.15rem 0;
  }

  .wire {
    flex: 1;
    width: auto;
  }

  .link-label {
    white-space: normal;
  }

  .wire-meta {
    display: none;
  }
}

@media (max-width: 560px) {
  /* 手机上把「编码」列收起，让 4 列在 390px 内可读完，不必横向拖动 */
  table {
    min-width: 0;
    font-size: 11.5px;
  }

  th,
  td {
    padding: 0.45rem 0.55rem;
  }

  th:last-child,
  td:last-child {
    display: none;
  }

  .bar-name {
    font-size: 11px;
  }
}

@media (max-width: 460px) {
  body {
    font-size: 14px;
  }

  .kv-row {
    font-size: 11.5px;
  }

  .foot-grid {
    flex-direction: column;
  }
}

@media (prefers-reduced-motion: reduce) {
  *,
  *::before,
  *::after {
    animation-duration: 0.001ms !important;
    animation-iteration-count: 1 !important;
    transition-duration: 0.001ms !important;
  }

  .wire::after {
    width: 100%;
    background: color-mix(in oklab, var(--primary) 40%, transparent);
    animation: none;
  }

  .card:hover,
  .btn:hover {
    transform: none;
  }
}

/* ---------- print ---------- */

@media print {
  .site-header,
  .actions,
  .wordmark {
    display: none;
  }

  body {
    background: #fff;
    color: #000;
  }
}