/* Design system v4 tokens (kb/00_core/DESIGN_SYSTEM_v4.md). Do not add colors outside this list. */
:root {
  --bg: #E9EAE4; --surface: #F6F6F2; --surface-sunk: #DDE0D7; --line: #D8D9D0;
  --text: #17302B; --text-body: #2E4440; --text-muted: #55625D;
  --action: #1F6B5E; --action-hover: #134A41; --on-action: #F6F6F2;
  --calm: #E3EEE9; --now: #E58B45; --now-text: #94501A; --now-tint: #FBEBDD;
  --pine: #17302B; --on-pine: #E9EAE4;
  --font-display: "Literata", Georgia, serif;
  --font-text: "Onest", system-ui, sans-serif;
  --font-data: "JetBrains Mono", ui-monospace, monospace;
  --radius-pill: 999px; --radius-field: 10px; --radius-card: 20px; --radius-block: 28px;
  --shadow-lift: inset 0 1px 0 rgba(255,255,255,.7), 0 1px 2px rgba(23,48,43,.06), 0 22px 44px -22px rgba(23,48,43,.32);
  --dur-quick: 240ms; --dur-calm: 480ms; --ease-calm: cubic-bezier(.22,.61,.36,1);
}
@media (prefers-color-scheme: dark) {
  :root {
    --bg: #121A19; --surface: #1B2523; --surface-sunk: #0F1716; --line: #2A3633;
    --text: #E6E8E2; --text-body: #C9D2CD; --text-muted: #9FB0A9;
    --action: #6FC2AE; --action-hover: #8FD3C2; --on-action: #0F1716; --calm: #1F3A35;
    --now: #F0A766; --now-text: #F0A766; --now-tint: #2E2318; --pine: #0F1716; --on-pine: #E6E8E2;
    --shadow-lift: 0 1px 2px rgba(0,0,0,.3);
  }
}
* { box-sizing: border-box; }
html { -webkit-text-size-adjust: 100%; }
body { margin: 0; background: var(--bg); color: var(--text-body); font: 400 18px/1.65 var(--font-text); }
a { color: var(--action); text-underline-offset: 3px; }
a:hover { color: var(--action-hover); }
img { max-width: 100%; display: block; }
.wrap { max-width: 1080px; margin: 0 auto; padding: 0 20px; }
.col { max-width: 700px; margin: 0 auto; padding: 0 20px; }
h1, h2, h3 { font-family: var(--font-display); font-weight: 600; color: var(--text); margin: 0 0 16px; letter-spacing: -0.015em; }
h1 { font-size: clamp(38px, 7vw, 64px); line-height: 1.05; }
h2 { font-size: clamp(28px, 4.5vw, 44px); line-height: 1.1; }
h3 { font-size: 24px; line-height: 1.2; }
p { margin: 0 0 16px; }
.lead { font-size: 21px; line-height: 1.55; color: var(--text-body); }
.muted { color: var(--text-muted); }
.data { font: 500 13px/1.5 var(--font-data); color: var(--text-muted); letter-spacing: .01em; }
section { padding: 56px 0; }

/* C-01 navigation */
.nav { display: flex; align-items: center; justify-content: space-between; gap: 12px; padding: 18px 20px; max-width: 1080px; margin: 0 auto; }
.brand { font-family: var(--font-display); font-weight: 600; font-size: 19px; color: var(--text); text-decoration: none; }
.nav ul { display: flex; gap: 6px; list-style: none; margin: 0; padding: 0; }
.nav a.pill { display: inline-block; padding: 9px 16px; border-radius: var(--radius-pill); color: var(--text); text-decoration: none; font-size: 15px; font-weight: 500; }
.nav a.pill:hover, .nav a.pill[aria-current="page"] { background: var(--surface); }

/* C-02 buttons */
.btn { display: inline-flex; align-items: center; justify-content: center; min-height: 48px; padding: 0 24px; border-radius: var(--radius-pill); border: 0; font: 500 16px var(--font-text); text-decoration: none; cursor: pointer; transition: background var(--dur-quick) var(--ease-calm); }
.btn-primary { background: var(--action); color: var(--on-action); }
.btn-primary:hover { background: var(--action-hover); color: var(--on-action); }
.btn-quiet { background: transparent; color: var(--action); box-shadow: inset 0 0 0 1.5px var(--line); }

/* hero */
.hero { padding: 48px 0 40px; }
.hero h1 { max-width: 14ch; }
.chips { display: flex; flex-wrap: wrap; gap: 8px; margin-top: 24px; }
.chip { display: inline-block; padding: 8px 14px; border-radius: var(--radius-pill); background: var(--surface); color: var(--text); font-size: 15px; text-decoration: none; box-shadow: inset 0 0 0 1px var(--line); }
.chip:hover { box-shadow: inset 0 0 0 1.5px var(--action); }

/* C-11 tool card */
.grid { display: grid; grid-template-columns: repeat(auto-fill, minmax(260px, 1fr)); gap: 16px; }
.card { display: flex; flex-direction: column; gap: 10px; padding: 24px; border-radius: var(--radius-card); background: var(--surface); box-shadow: var(--shadow-lift); text-decoration: none; color: var(--text-body); transition: transform var(--dur-quick) var(--ease-calm); }
.card:hover { transform: translateY(-2px); }
.card h3 { margin: 0; font-size: 22px; }
.card .rubric { font: 500 13px var(--font-data); color: var(--text-muted); text-transform: uppercase; letter-spacing: .06em; }
.card .go { margin-top: auto; color: var(--action); font-weight: 500; font-size: 15px; }
.group-title { margin: 40px 0 16px; font-size: 26px; }

/* T-05 tool page */
.tool-head { padding: 40px 0 8px; }
.short { background: var(--calm); border-radius: var(--radius-card); padding: 20px 24px; margin: 24px 0; }
.short .data { display: block; margin-bottom: 6px; }
.form { background: var(--surface); border-radius: var(--radius-block); padding: 28px 24px; box-shadow: var(--shadow-lift); margin: 24px 0; }
.field { margin-bottom: 22px; }
.field label { display: block; font: 500 16px/1.4 var(--font-text); color: var(--text); margin-bottom: 8px; }
.field .hint { display: block; font-size: 14px; color: var(--text-muted); margin-top: 6px; }
.field input, .field select { width: 100%; min-height: 52px; padding: 0 16px; border-radius: var(--radius-field); border: 1.5px solid var(--line); background: var(--bg); color: var(--text); font: 500 20px var(--font-text); }
.field input:focus, .field select:focus { outline: none; border-color: var(--action); }
.seg { display: flex; gap: 8px; flex-wrap: wrap; }
.seg label { margin: 0; }
.seg input { position: absolute; opacity: 0; width: 1px; height: 1px; }
.seg span { display: inline-flex; align-items: center; min-height: 44px; padding: 0 18px; border-radius: var(--radius-pill); box-shadow: inset 0 0 0 1.5px var(--line); cursor: pointer; font-size: 16px; color: var(--text); }
.seg input:checked + span { background: var(--action); color: var(--on-action); box-shadow: none; }
.seg input:focus-visible + span { outline: 2px solid var(--action); outline-offset: 2px; }
.result { margin: 8px 0 0; padding: 28px 24px; border-radius: var(--radius-block); background: var(--pine); color: var(--on-pine); }
.result .num { font: 600 clamp(44px, 10vw, 72px)/1 var(--font-display); color: var(--on-pine); margin: 6px 0 12px; }
.result p { color: var(--on-pine); margin: 0 0 10px; }
.result .data { color: var(--on-pine); opacity: .75; }
.result .rows { display: grid; gap: 6px; margin: 14px 0; font-size: 16px; }
.result .rows div { display: flex; justify-content: space-between; gap: 12px; border-bottom: 1px solid rgba(233,234,228,.18); padding-bottom: 6px; }
.thought { font: italic 400 clamp(24px, 4vw, 32px)/1.3 var(--font-display); color: var(--text); padding: 40px 0; margin: 0; }
.gap { background: var(--now-tint); border-radius: var(--radius-card); padding: 18px 22px; margin: 20px 0; }
.gap strong { color: var(--now-text); }
.steps { padding-left: 22px; } .steps li { margin-bottom: 8px; }
.formula { background: var(--surface-sunk); border-radius: var(--radius-card); padding: 18px 22px; font: 500 14px/1.7 var(--font-data); color: var(--text-body); overflow-x: auto; }
details { border-top: 1px solid var(--line); padding: 14px 0; }
details summary { cursor: pointer; font-weight: 500; color: var(--text); font-size: 17px; }
details p { margin-top: 10px; }
.passport { font: 500 12.5px/1.5 var(--font-data); color: var(--text-muted); }
.sources li { font-size: 15px; margin-bottom: 6px; }

/* C-16 author + C-12 door */
.author { display: flex; gap: 16px; align-items: center; padding: 24px 0; border-top: 1px solid var(--line); margin-top: 32px; }
.author img { width: 56px; height: 56px; border-radius: 50%; object-fit: cover; }
.door { background: var(--surface); border-radius: var(--radius-block); padding: 28px 24px; margin: 32px 0; display: flex; flex-wrap: wrap; align-items: center; justify-content: space-between; gap: 16px; }
.door p { margin: 0; font-size: 19px; color: var(--text); }

footer { padding: 40px 0 56px; border-top: 1px solid var(--line); margin-top: 48px; }
footer p { font-size: 14px; color: var(--text-muted); }

@media (max-width: 560px) {
  .nav ul { gap: 2px; } .nav a.pill { padding: 8px 10px; font-size: 14px; }
  section { padding: 40px 0; }
}
@media (prefers-reduced-motion: reduce) { * { transition: none !important; animation: none !important; } }