/* RetentionLab landing page. One coherent visual system, no framework. */

:root {
  --background: #0a0c10;
  --surface: #12151c;
  --surface-secondary: #171b24;
  --text: #eef2f8;
  --muted: #8b95a8;
  --accent: #6c8cff;
  --accent-soft: rgba(108, 140, 255, 0.12);
  --accent-line: rgba(108, 140, 255, 0.35);
  --border: #232937;
  --success: #3fcf8e;
  --warning: #e3b341;
  --danger: #f2777a;

  --radius: 12px;
  --radius-sm: 8px;
  --maxw: 1120px;
  --gutter: 24px;
  --mono: ui-monospace, SFMono-Regular, "SF Mono", Menlo, Consolas, monospace;
  --sans: -apple-system, BlinkMacSystemFont, "Segoe UI", Inter, Roboto, Helvetica, Arial,
          sans-serif;
}

* { box-sizing: border-box; }

html { scroll-behavior: smooth; scroll-padding-top: 76px; }

body {
  margin: 0;
  background: var(--background);
  color: var(--text);
  font-family: var(--sans);
  font-size: 16px;
  line-height: 1.6;
  -webkit-font-smoothing: antialiased;
}

a { color: inherit; }

/* ---------- Layout ---------- */

.wrap { width: 100%; max-width: var(--maxw); margin: 0 auto; padding: 0 var(--gutter); }

section { padding: 84px 0; border-top: 1px solid var(--border); }
section:first-of-type { border-top: none; }

.eyebrow {
  font-size: 0.72rem;
  font-weight: 650;
  letter-spacing: 0.16em;
  text-transform: uppercase;
  color: var(--accent);
  margin: 0 0 12px;
}

h1, h2, h3 { letter-spacing: -0.022em; margin: 0; }

h2 { font-size: clamp(1.6rem, 3.2vw, 2.05rem); font-weight: 640; margin-bottom: 14px; }
h3 { font-size: 1.02rem; font-weight: 620; }

.lede { color: var(--muted); font-size: 1.03rem; max-width: 68ch; margin: 0 0 36px; }
.note { color: var(--muted); font-size: 0.86rem; line-height: 1.6; }
.note-strong { color: var(--text); font-weight: 600; }

code, .mono { font-family: var(--mono); font-size: 0.88em; }

/* ---------- Navigation ---------- */

.nav {
  position: sticky; top: 0; z-index: 50;
  background: rgba(10, 12, 16, 0.86);
  backdrop-filter: blur(10px);
  border-bottom: 1px solid var(--border);
}
.nav-inner {
  display: flex; align-items: center; gap: 20px;
  height: 60px;
  max-width: var(--maxw); margin: 0 auto; padding: 0 var(--gutter);
}
.brand {
  font-weight: 700; font-size: 0.95rem; letter-spacing: 0.02em;
  text-decoration: none; white-space: nowrap;
}
.brand span { color: var(--accent); }
.nav-links {
  display: flex; gap: 4px; margin-left: auto;
  overflow-x: auto; scrollbar-width: none; -ms-overflow-style: none;
}
.nav-links::-webkit-scrollbar { display: none; }
.nav-links a {
  padding: 7px 11px; border-radius: var(--radius-sm);
  font-size: 0.855rem; color: var(--muted); text-decoration: none;
  white-space: nowrap; transition: color 0.15s ease, background 0.15s ease;
}
.nav-links a:hover { color: var(--text); background: var(--surface-secondary); }
.nav-cta {
  flex-shrink: 0; padding: 7px 14px; border-radius: var(--radius-sm);
  border: 1px solid var(--border); background: var(--surface);
  font-size: 0.855rem; font-weight: 600; text-decoration: none;
  transition: border-color 0.15s ease;
}
.nav-cta:hover { border-color: var(--accent-line); }

/* ---------- Hero ---------- */

.hero { padding: 92px 0 76px; border-top: none; }
.hero-title {
  font-size: clamp(2.4rem, 6.4vw, 3.9rem);
  font-weight: 700; line-height: 1.04; margin: 0 0 14px;
}
.hero-sub {
  font-size: clamp(1.02rem, 2.2vw, 1.22rem);
  color: var(--text); font-weight: 500; margin: 0 0 18px;
}
.hero-copy { color: var(--muted); max-width: 62ch; font-size: 1rem; margin: 0 0 32px; }

.cta-row { display: flex; flex-wrap: wrap; gap: 10px; margin-bottom: 56px; }
.btn {
  display: inline-flex; align-items: center; gap: 7px;
  padding: 11px 19px; border-radius: var(--radius-sm);
  font-size: 0.92rem; font-weight: 600; text-decoration: none;
  border: 1px solid var(--border); background: var(--surface); color: var(--text);
  cursor: pointer; transition: border-color 0.15s ease, background 0.15s ease;
}
.btn:hover { border-color: var(--accent-line); background: var(--surface-secondary); }
.btn-primary {
  background: var(--accent); border-color: var(--accent); color: #080b14;
}
.btn-primary:hover { background: #7f9bff; border-color: #7f9bff; }

/* ---------- Metric cards ---------- */

.metrics {
  display: grid; gap: 14px;
  grid-template-columns: repeat(auto-fit, minmax(190px, 1fr));
}
.metric {
  background: var(--surface); border: 1px solid var(--border);
  border-radius: var(--radius); padding: 22px 20px;
  transition: border-color 0.18s ease, transform 0.18s ease;
}
.metric:hover { border-color: var(--accent-line); transform: translateY(-2px); }
.metric-value {
  font-size: clamp(1.85rem, 4vw, 2.3rem); font-weight: 700;
  letter-spacing: -0.03em; line-height: 1.1; font-variant-numeric: tabular-nums;
}
.metric-label { font-size: 0.9rem; font-weight: 560; margin-top: 6px; }
.metric-detail { font-size: 0.78rem; color: var(--muted); margin-top: 5px; line-height: 1.45; }

/* ---------- Generic cards & grids ---------- */

.card {
  background: var(--surface); border: 1px solid var(--border);
  border-radius: var(--radius); padding: 22px;
}
.grid-2 { display: grid; gap: 16px; grid-template-columns: repeat(auto-fit, minmax(300px, 1fr)); }
.grid-3 { display: grid; gap: 14px; grid-template-columns: repeat(auto-fit, minmax(240px, 1fr)); }

.stat-card .stat-value {
  font-size: 2rem; font-weight: 700; letter-spacing: -0.03em;
  font-variant-numeric: tabular-nums;
}
.stat-card .stat-label { font-size: 0.85rem; font-weight: 560; margin-top: 4px; }
.stat-card .stat-detail { font-size: 0.78rem; color: var(--muted); margin-top: 6px; }

.accent { color: var(--accent); }
.success { color: var(--success); }
.warning { color: var(--warning); }
.danger { color: var(--danger); }

/* ---------- Decision flow ---------- */

.flow { display: grid; gap: 10px; }
.flow-step {
  display: grid; grid-template-columns: 34px 1fr; gap: 14px; align-items: start;
  background: var(--surface); border: 1px solid var(--border);
  border-radius: var(--radius); padding: 15px 18px;
  transition: border-color 0.18s ease;
}
.flow-step:hover { border-color: var(--accent-line); }
.flow-index {
  width: 26px; height: 26px; border-radius: 50%;
  display: grid; place-items: center;
  background: var(--accent-soft); color: var(--accent);
  font-size: 0.76rem; font-weight: 700; font-family: var(--mono);
}
.flow-step h3 { font-size: 0.97rem; }
.flow-step p { margin: 3px 0 0; font-size: 0.85rem; color: var(--muted); }
.flow-step.terminal { border-color: var(--accent-line); background: var(--surface-secondary); }

/* ---------- Bar chart (policy) ---------- */

.bars { display: grid; gap: 18px; margin: 8px 0 4px; }
.bar-row { display: grid; gap: 8px; }
.bar-head {
  display: flex; justify-content: space-between; align-items: baseline; gap: 12px;
  font-size: 0.88rem;
}
.bar-capacity { font-weight: 640; font-family: var(--mono); }
.bar-value { font-variant-numeric: tabular-nums; color: var(--muted); }
.bar-value b { color: var(--text); font-size: 1.02rem; }
.bar-track {
  position: relative; height: 34px; border-radius: var(--radius-sm);
  background: var(--surface-secondary); border: 1px solid var(--border);
  overflow: hidden;
}
.bar-fill {
  height: 100%;
  background: linear-gradient(90deg, rgba(108, 140, 255, 0.55), var(--accent));
  border-radius: var(--radius-sm) 0 0 var(--radius-sm);
  animation: grow 0.9s cubic-bezier(0.22, 1, 0.36, 1) both;
}
.bar-row.is-highlight .bar-fill { background: linear-gradient(90deg, #2f9c74, var(--success)); }
.bar-random {
  position: absolute; top: 0; bottom: 0; width: 2px;
  background: var(--muted); opacity: 0.75;
}
.bar-random::after {
  content: attr(data-label); position: absolute; top: 50%; left: 8px;
  transform: translateY(-50%); font-size: 0.68rem; color: var(--muted); white-space: nowrap;
}
@keyframes grow { from { width: 0; } }

.pill {
  display: inline-block; padding: 3px 9px; border-radius: 999px;
  font-size: 0.72rem; font-weight: 650; letter-spacing: 0.02em;
  border: 1px solid var(--border); background: var(--surface-secondary); color: var(--muted);
}
.pill.is-on { border-color: var(--accent-line); color: var(--accent); background: var(--accent-soft); }

/* ---------- Highlight strip ---------- */

.chain {
  display: flex; flex-wrap: wrap; align-items: center; gap: 12px;
  padding: 20px; border-radius: var(--radius);
  border: 1px solid var(--accent-line); background: var(--accent-soft);
  margin-top: 22px;
}
.chain-item { display: grid; }
.chain-item b { font-size: 1.25rem; letter-spacing: -0.02em; font-variant-numeric: tabular-nums; }
.chain-item span { font-size: 0.78rem; color: var(--muted); }
.chain-arrow { color: var(--accent); font-size: 1.1rem; }

/* ---------- Figures ---------- */

.figures { display: grid; gap: 16px; grid-template-columns: repeat(auto-fit, minmax(300px, 1fr)); }
figure {
  margin: 0; background: var(--surface); border: 1px solid var(--border);
  border-radius: var(--radius); overflow: hidden;
}
figure img {
  display: block; width: 100%; height: auto;
  background: #ffffff; /* matplotlib figures render on white */
}
figcaption { padding: 13px 16px; border-top: 1px solid var(--border); }
figcaption b { display: block; font-size: 0.88rem; font-weight: 620; }
figcaption span { font-size: 0.78rem; color: var(--muted); }

/* ---------- Tables ---------- */

.table-scroll { overflow-x: auto; }
table { width: 100%; border-collapse: collapse; font-size: 0.88rem; min-width: 440px; }
th, td { text-align: left; padding: 11px 14px; border-bottom: 1px solid var(--border); }
th {
  font-size: 0.72rem; text-transform: uppercase; letter-spacing: 0.08em;
  color: var(--muted); font-weight: 640;
}
td { font-variant-numeric: tabular-nums; }
tr.is-selected td { background: var(--accent-soft); }
tr:last-child td { border-bottom: none; }

/* ---------- Forms / demo ---------- */

.form-grid { display: grid; gap: 20px; grid-template-columns: repeat(auto-fit, minmax(230px, 1fr)); }
.field-group h3 {
  font-size: 0.72rem; text-transform: uppercase; letter-spacing: 0.12em;
  color: var(--muted); margin-bottom: 12px; font-weight: 650;
}
.field { margin-bottom: 11px; }
.field label { display: block; font-size: 0.78rem; color: var(--muted); margin-bottom: 4px; }
select, input[type="number"] {
  width: 100%; padding: 9px 11px; border-radius: var(--radius-sm);
  border: 1px solid var(--border); background: var(--background); color: var(--text);
  font-size: 0.88rem; font-family: inherit;
}
select:focus, input:focus { outline: 2px solid var(--accent-line); outline-offset: 1px; }
input[type="range"] { width: 100%; accent-color: var(--accent); }
.range-value { font-family: var(--mono); font-size: 0.82rem; color: var(--text); }

.demo-actions {
  display: flex; flex-wrap: wrap; gap: 10px; align-items: center;
  margin-top: 20px; padding-top: 20px; border-top: 1px solid var(--border);
}
button { font-family: inherit; }
button:disabled { opacity: 0.55; cursor: default; }

/* ---------- Prediction result ---------- */

.result { margin-top: 20px; display: none; }
.result.is-visible { display: block; animation: fade 0.35s ease both; }
@keyframes fade { from { opacity: 0; transform: translateY(6px); } }

.result-head { display: flex; align-items: baseline; gap: 14px; flex-wrap: wrap; }
.result-prob {
  font-size: clamp(2.6rem, 7vw, 3.4rem); font-weight: 700;
  letter-spacing: -0.035em; line-height: 1; font-variant-numeric: tabular-nums;
}
.result-meter {
  position: relative; height: 12px; border-radius: 999px; margin: 16px 0 10px;
  background: var(--surface-secondary); border: 1px solid var(--border); overflow: hidden;
}
.result-meter-fill {
  height: 100%; width: 0; border-radius: 999px;
  transition: width 0.6s cubic-bezier(0.22, 1, 0.36, 1);
}
.band-success { background: var(--success); }
.band-warning { background: var(--warning); }
.band-danger { background: var(--danger); }
.result-meta {
  display: grid; gap: 10px; margin-top: 16px;
  grid-template-columns: repeat(auto-fit, minmax(150px, 1fr));
}
.result-meta div { background: var(--surface-secondary); border-radius: var(--radius-sm); padding: 11px 13px; }
.result-meta dt { font-size: 0.7rem; text-transform: uppercase; letter-spacing: 0.08em; color: var(--muted); }
.result-meta dd { margin: 3px 0 0; font-size: 0.86rem; font-family: var(--mono); word-break: break-word; }
.error-text { color: var(--danger); font-size: 0.88rem; }

/* ---------- Ranking demo ---------- */

.rank-controls { display: flex; flex-wrap: wrap; gap: 8px; align-items: center; margin-bottom: 18px; }
.seg {
  display: inline-flex; border: 1px solid var(--border);
  border-radius: var(--radius-sm); overflow: hidden;
}
.seg button {
  padding: 8px 16px; border: none; background: var(--surface); color: var(--muted);
  font-size: 0.86rem; font-weight: 600; cursor: pointer;
  border-right: 1px solid var(--border); transition: background 0.15s ease, color 0.15s ease;
}
.seg button:last-child { border-right: none; }
.seg button.is-active { background: var(--accent); color: #080b14; }

.rank-list { display: grid; gap: 7px; }
.rank-row {
  display: grid; grid-template-columns: 40px 108px 1fr 74px 104px; gap: 12px;
  align-items: center; padding: 10px 14px;
  background: var(--surface); border: 1px solid var(--border); border-radius: var(--radius-sm);
  font-size: 0.85rem;
}
.rank-row.is-selected { border-color: var(--accent-line); background: var(--accent-soft); }
.rank-num { font-family: var(--mono); color: var(--muted); font-variant-numeric: tabular-nums; }
.rank-id { font-family: var(--mono); font-size: 0.82rem; }
.rank-bar { height: 8px; border-radius: 999px; background: var(--surface-secondary); overflow: hidden; }
.rank-bar-fill { height: 100%; background: var(--accent); border-radius: 999px; }
.rank-row.is-selected .rank-bar-fill { background: var(--success); }
.rank-prob { font-variant-numeric: tabular-nums; text-align: right; font-weight: 600; }
.rank-flag { font-size: 0.72rem; text-align: right; color: var(--muted); }
.rank-row.is-selected .rank-flag { color: var(--success); font-weight: 640; }

/* ---------- Experiment ---------- */

.arms { display: grid; gap: 14px; grid-template-columns: 1fr auto 1fr; align-items: center; }
.arm {
  text-align: center; padding: 26px 20px; border-radius: var(--radius);
  border: 1px solid var(--border); background: var(--surface);
}
.arm.is-treatment { border-color: var(--accent-line); background: var(--accent-soft); }
.arm-label {
  font-size: 0.72rem; text-transform: uppercase; letter-spacing: 0.12em;
  color: var(--muted); font-weight: 650;
}
.arm-value {
  font-size: clamp(1.9rem, 5vw, 2.5rem); font-weight: 700;
  letter-spacing: -0.03em; margin-top: 6px; font-variant-numeric: tabular-nums;
}
.arm-unit { font-size: 0.78rem; color: var(--muted); }
.arm-vs { font-size: 0.82rem; color: var(--muted); font-weight: 650; }

/* ---------- Architecture ---------- */

.arch { display: grid; gap: 16px; grid-template-columns: repeat(auto-fit, minmax(290px, 1fr)); }
.arch-col { background: var(--surface); border: 1px solid var(--border); border-radius: var(--radius); padding: 20px; }
.arch-col > .eyebrow { margin-bottom: 16px; }
.arch-stage { position: relative; padding: 0 0 0 26px; margin-bottom: 14px; }
.arch-stage:last-child { margin-bottom: 0; }
.arch-stage::before {
  content: ""; position: absolute; left: 5px; top: 6px;
  width: 8px; height: 8px; border-radius: 50%;
  background: var(--accent); box-shadow: 0 0 0 3px var(--accent-soft);
}
.arch-stage::after {
  content: ""; position: absolute; left: 8.5px; top: 18px; bottom: -14px;
  width: 1px; background: var(--border);
}
.arch-stage:last-child::after { display: none; }
.arch-stage b { display: block; font-size: 0.89rem; font-weight: 620; }
.arch-stage span { font-size: 0.78rem; color: var(--muted); }
.arch-fanout { display: flex; flex-wrap: wrap; gap: 6px; margin-top: 10px; }
.arch-fanout code {
  padding: 4px 9px; border-radius: 999px;
  border: 1px solid var(--border); background: var(--surface-secondary);
  font-size: 0.75rem; color: var(--text);
}

/* ---------- PSI scale ---------- */

.psi-scale { display: grid; gap: 8px; margin-top: 14px; }
.psi-band {
  display: grid; grid-template-columns: 92px 1fr; gap: 14px; align-items: center;
  padding: 11px 14px; border-radius: var(--radius-sm);
  background: var(--surface-secondary); border: 1px solid var(--border);
}
.psi-range { font-family: var(--mono); font-size: 0.82rem; font-weight: 640; }
.psi-meaning { font-size: 0.85rem; color: var(--muted); }
.psi-band.tone-success { border-left: 3px solid var(--success); }
.psi-band.tone-warning { border-left: 3px solid var(--warning); }
.psi-band.tone-danger { border-left: 3px solid var(--danger); }

/* ---------- Benchmark chart ---------- */

.bench { display: grid; gap: 12px; }
.bench-row { display: grid; grid-template-columns: 82px 1fr 96px; gap: 12px; align-items: center; }
.bench-label { font-family: var(--mono); font-size: 0.82rem; color: var(--muted); }
.bench-track { height: 26px; background: var(--surface-secondary); border: 1px solid var(--border); border-radius: var(--radius-sm); overflow: hidden; }
.bench-fill { height: 100%; background: linear-gradient(90deg, rgba(108,140,255,0.5), var(--accent)); }
.bench-value { font-variant-numeric: tabular-nums; font-size: 0.85rem; text-align: right; }

/* ---------- Tech stack ---------- */

.stack { display: grid; gap: 10px; grid-template-columns: repeat(auto-fill, minmax(168px, 1fr)); }
.stack-item {
  padding: 13px 15px; border-radius: var(--radius-sm);
  border: 1px solid var(--border); background: var(--surface);
  transition: border-color 0.15s ease;
}
.stack-item:hover { border-color: var(--accent-line); }
.stack-item b { display: block; font-size: 0.88rem; font-weight: 620; }
.stack-item span { font-size: 0.75rem; color: var(--muted); }

/* ---------- Endpoint links ---------- */

.endpoints { display: grid; gap: 9px; grid-template-columns: repeat(auto-fit, minmax(250px, 1fr)); }
.endpoint {
  display: flex; align-items: center; gap: 12px;
  padding: 13px 16px; border-radius: var(--radius-sm);
  border: 1px solid var(--border); background: var(--surface);
  text-decoration: none; transition: border-color 0.15s ease, transform 0.15s ease;
}
.endpoint:hover { border-color: var(--accent-line); transform: translateX(2px); }
.endpoint-path { font-family: var(--mono); font-size: 0.85rem; font-weight: 620; }
.endpoint-desc { font-size: 0.76rem; color: var(--muted); }
.endpoint-arrow { margin-left: auto; color: var(--muted); }

/* ---------- Limitations ---------- */

.limits { display: grid; gap: 9px; }
.limit {
  display: grid; grid-template-columns: 18px 1fr; gap: 12px; align-items: start;
  font-size: 0.88rem; color: var(--muted);
  padding: 12px 15px; background: var(--surface); border: 1px solid var(--border);
  border-radius: var(--radius-sm);
}
.limit svg { margin-top: 3px; color: var(--warning); flex-shrink: 0; }

/* ---------- Footer ---------- */

footer { border-top: 1px solid var(--border); padding: 34px 0 52px; }
.footer-inner { display: flex; flex-wrap: wrap; gap: 16px; justify-content: space-between; }

/* ---------- Responsive ---------- */

@media (max-width: 860px) {
  section { padding: 62px 0; }
  .hero { padding: 60px 0 54px; }
  .arms { grid-template-columns: 1fr; }
  .arm-vs { text-align: center; }
  .rank-row { grid-template-columns: 32px 1fr 66px; row-gap: 8px; }
  .rank-bar { grid-column: 1 / -1; }
  .rank-flag { grid-column: 1 / -1; text-align: left; }
}

@media (max-width: 560px) {
  :root { --gutter: 18px; }
  .nav-links { display: none; }
  .metric { padding: 18px 16px; }
  .btn { flex: 1 1 auto; justify-content: center; }
}

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