/* Layout concept: a calm docs-first site. Home explains the argument with one diagram,
   Docs gets a left rail, contents rail and long-form reading column. */
:root {
  --bg: #f6f8f8;
  --surface: #ffffff;
  --surface-2: #eaf0f0;
  --ink: #11181a;
  --ink-2: #455356;
  --line: #d6dfe0;
  --accent: #0a6b5c;
  --accent-ink: #ffffff;
  --accent-soft: #dcf0eb;
  --flag: #8a4a06;
  --flag-bg: #fdefd2;
  --flag-line: #e3b866;
  --f-display: 'Bricolage Grotesque', 'Segoe UI', system-ui, sans-serif;
  --f-body: 'Public Sans', 'Segoe UI', system-ui, sans-serif;
  --f-mono: 'JetBrains Mono', ui-monospace, Consolas, monospace;
  --head-h: 64px;
}
@media (prefers-color-scheme: dark) {
  :root:not([data-theme="light"]) {
    --bg: #0d1314; --surface: #131b1d; --surface-2: #1a2527; --ink: #e8eeee; --ink-2: #a0aeb1;
    --line: #263336; --accent: #3cc5aa; --accent-ink: #06201b; --accent-soft: #12332e;
    --flag: #f2b95c; --flag-bg: #35290f; --flag-line: #6b5420;
    color-scheme: dark;
  }
}
:root[data-theme="dark"] {
  --bg: #0d1314; --surface: #131b1d; --surface-2: #1a2527; --ink: #e8eeee; --ink-2: #a0aeb1;
  --line: #263336; --accent: #3cc5aa; --accent-ink: #06201b; --accent-soft: #12332e;
  --flag: #f2b95c; --flag-bg: #35290f; --flag-line: #6b5420;
  color-scheme: dark;
}
* { box-sizing: border-box; }
html { scroll-behavior: smooth; }
@media (prefers-reduced-motion: reduce) { html { scroll-behavior: auto; } * { transition: none !important; } }
body { background: var(--bg); color: var(--ink); font: 400 17px/1.6 var(--f-body); }
body::before { content: ""; position: fixed; inset: 0 0 auto; height: env(safe-area-inset-top, 0px); background: var(--bg); z-index: 30; }
a { color: var(--accent); text-underline-offset: 3px; }
a:hover { text-decoration-thickness: 2px; }
:focus-visible { outline: 2px solid var(--accent); outline-offset: 2px; border-radius: 3px; }
.wrap { width: 100%; max-width: 1240px; margin: 0 auto; padding-left: max(16px, env(safe-area-inset-left, 0px)); padding-right: max(16px, env(safe-area-inset-right, 0px)); }

/* header */
.site-head { position: sticky; top: env(safe-area-inset-top, 0px); z-index: 20; background: var(--bg); border-bottom: 1px solid var(--line); }
.bar { display: flex; align-items: center; gap: 20px; min-height: var(--head-h); flex-wrap: wrap; padding-block: 8px; }
.logo { display: inline-flex; align-items: center; gap: 10px; font: 600 1.25rem/1 var(--f-display); color: var(--ink); text-decoration: none; letter-spacing: -0.01em; }
.logo svg { width: 28px; height: 28px; }
.nav { display: flex; gap: 4px; flex-wrap: wrap; margin-left: 8px; }
.nav a { color: var(--ink-2); text-decoration: none; padding: 6px 12px; border-radius: 6px; font-weight: 500; font-size: .95rem; }
.nav a:hover { background: var(--surface-2); color: var(--ink); }
.nav a[aria-current="page"] { color: var(--accent); background: var(--accent-soft); }
.tools { margin-left: auto; display: flex; align-items: center; gap: 8px; flex-wrap: wrap; }
.btn { display: inline-flex; align-items: center; gap: 8px; padding: 10px 18px; border-radius: 6px; font: 600 .95rem/1.2 var(--f-body); text-decoration: none; border: 1px solid transparent; cursor: pointer; }
.btn-primary { background: var(--accent); color: var(--accent-ink); }
.btn-primary:hover { filter: brightness(1.08); text-decoration: none; }
.btn-ghost { border-color: var(--line); color: var(--ink); background: var(--surface); }
.btn-ghost:hover { border-color: var(--accent); text-decoration: none; }
.btn-sm { padding: 7px 12px; font-size: .85rem; }
.tgl { appearance: none; border: 1px solid var(--line); background: var(--surface); color: var(--ink-2); border-radius: 6px; padding: 7px 10px; font: 500 .8rem/1 var(--f-body); cursor: pointer; }
.daynight { padding: 0; border: 0; background: none; cursor: pointer; border-radius: 999px; line-height: 0; }
.dn-track { display: block; position: relative; width: 58px; height: 30px; border-radius: 999px; background: #bfe0ea; border: 1px solid #98c4d3; transition: background .25s, border-color .25s; overflow: hidden; }
.dn-knob { position: absolute; top: 3px; left: 3px; width: 22px; height: 22px; border-radius: 50%; background: #ffffff; display: grid; place-items: center; transition: transform .25s, background .25s; box-shadow: 0 1px 2px rgba(0,0,0,.25); }
.dn-sun, .dn-moon { grid-area: 1 / 1; width: 15px; height: 15px; }
.dn-sun { color: #e39a0e; }
.dn-moon { color: #5f6fb0; display: none; }
.dn-stars i { position: absolute; width: 2px; height: 2px; border-radius: 50%; background: #cfd8ee; opacity: 0; transition: opacity .25s; }
.dn-stars i:nth-child(1) { left: 11px; top: 8px; }
.dn-stars i:nth-child(2) { left: 19px; top: 17px; }
.dn-stars i:nth-child(3) { left: 8px; top: 20px; }
.daynight[aria-checked="true"] .dn-track { background: #16243a; border-color: #2e4a6b; }
.daynight[aria-checked="true"] .dn-knob { transform: translateX(28px); background: #dfe6f2; }
.daynight[aria-checked="true"] .dn-sun { display: none; }
.daynight[aria-checked="true"] .dn-moon { display: block; }
.daynight[aria-checked="true"] .dn-stars i { opacity: 1; }

/* home */
.hero { padding-block: 72px 64px; }
.hero-grid { display: grid; grid-template-columns: minmax(0, 1.05fr) minmax(0, 1fr); gap: 48px; align-items: center; }
.eyebrow { font: 500 .78rem/1 var(--f-mono); text-transform: uppercase; letter-spacing: .08em; color: var(--ink-2); margin: 0 0 16px; }
h1, h2, h3, h4 { font-family: var(--f-display); letter-spacing: -0.015em; text-wrap: balance; }
.hero h1 { font-size: clamp(2.3rem, 5.2vw, 3.9rem); line-height: 1.04; font-weight: 600; margin: 0 0 22px; max-width: 18ch; }
.hero .sub { font-size: 1.3rem; color: var(--ink-2); margin: 0 0 30px; max-width: 40ch; }
.hero .cta-row { display: flex; gap: 12px; flex-wrap: wrap; margin-bottom: 24px; }
.hero .note p { margin: 0; color: var(--ink-2); font-size: .95rem; }
.figure { background: var(--surface); border: 1px solid var(--line); border-radius: 8px; padding: 16px; }
.figure svg { display: block; width: 100%; height: auto; }
.figure.plain { background: none; border: 0; padding: 0; }
.fig-light { display: none; }
:root[data-theme="light"] .fig-light { display: block; }
:root[data-theme="light"] .fig-dark { display: none; }
.figure figcaption { font-size: .88rem; color: var(--ink-2); margin-top: 8px; }
.band { padding-block: 56px; border-top: 1px solid var(--line); }
.band.alt { background: var(--surface); }
.band h2 { font-size: clamp(1.6rem, 3vw, 2.1rem); margin: 0 0 24px; line-height: 1.15; font-weight: 600; }
.split { display: grid; grid-template-columns: minmax(0, 1fr) minmax(0, 1.6fr); gap: 48px; }
.essay p { font-size: 1.1rem; margin: 0 0 1.1em; max-width: 62ch; }
.beats { border-bottom: 1px solid var(--line); }
.beat { display: grid; grid-template-columns: minmax(0, 1fr) minmax(0, 1.6fr); gap: 48px; padding: 30px 0; border-top: 1px solid var(--line); }
.beat h3 { margin: 0; font-size: 1.4rem; line-height: 1.2; font-weight: 600; max-width: 16ch; }
.beat p { margin: 0; font-size: 1.1rem; max-width: 60ch; }
.beats-more { margin-top: 24px; font-size: 1.05rem; }
.beats-more p { margin: 0; }
.cards { display: grid; grid-template-columns: repeat(2, minmax(0, 1fr)); gap: 16px; }
.card { background: var(--surface); border: 1px solid var(--line); border-radius: 8px; padding: 22px; }
.band.alt .card { background: var(--bg); }
.card h3 { margin: 0 0 8px; font-size: 1.15rem; font-weight: 600; }
.card p { margin: 0; color: var(--ink-2); font-size: .98rem; }
.card .more { margin-top: 14px; font-weight: 600; font-size: .95rem; }
.changes { list-style: none; margin: 0; padding: 0; display: grid; grid-template-columns: repeat(2, minmax(0, 1fr)); gap: 0 40px; }
.changes li { padding: 16px 0; border-top: 1px solid var(--line); color: var(--ink-2); }
.changes li strong { display: block; color: var(--ink); font-family: var(--f-display); font-weight: 600; font-size: 1.08rem; margin-bottom: 4px; }
.status { display: grid; grid-template-columns: repeat(3, minmax(0, 1fr)); gap: 16px; margin-top: 8px; }
.status .card { border-top: 3px solid var(--accent); }
.status .card.progress { border-top-style: dashed; border-top-color: var(--flag-line); }
.status .card.today { border-top-color: var(--ink-2); }
.status .tag { font: 500 .72rem/1 var(--f-mono); text-transform: uppercase; letter-spacing: .08em; color: var(--ink-2); margin-bottom: 10px; display: block; }
.intro { color: var(--ink-2); margin: -8px 0 20px; }
.start { display: grid; grid-template-columns: repeat(3, minmax(0, 1fr)); gap: 16px; }
.stay { display: grid; grid-template-columns: minmax(0, 1fr) minmax(0, 1.2fr); gap: 48px; align-items: center; }
.stay p { margin: 0; color: var(--ink-2); font-size: 1.1rem; }
.stay h2 { margin-bottom: 12px; }
.sub-form { display: flex; flex-wrap: wrap; gap: 10px; }
.sub-form input { flex: 1 1 220px; min-width: 0; padding: 11px 14px; border: 1px solid var(--line); border-radius: 6px; background: var(--surface); color: var(--ink); font: inherit; }
.sub-form .msg { flex-basis: 100%; font-size: .92rem; min-height: 1.4em; color: var(--ink-2); }
.sub-form .msg.err { color: var(--flag); }
.sub-form .msg.ok { color: var(--accent); }
.sub-form .proto { flex-basis: 100%; font: 400 .75rem/1.4 var(--f-mono); color: var(--ink-2); }

/* footer */
.site-foot { border-top: 1px solid var(--line); padding-block: 32px 48px; color: var(--ink-2); font-size: .92rem; }
.site-foot .row { display: flex; gap: 12px 24px; flex-wrap: wrap; align-items: center; }
.site-foot a { color: var(--ink-2); }
.site-foot .copy { margin-left: auto; }

/* docs layout */
.docs { display: grid; grid-template-columns: 270px minmax(0, 1fr) 210px; gap: 40px; padding-block: 32px 72px; align-items: start; }
.side { position: sticky; top: calc(env(safe-area-inset-top, 0px) + var(--head-h) + 16px); max-height: calc(100vh - var(--head-h) - 32px); overflow: auto; font-size: .93rem; padding-right: 8px; }
.side > summary { display: none; }
.side ul { list-style: none; margin: 0; padding: 0; }
.g { margin-bottom: 6px; }
.g-head { display: flex; align-items: baseline; gap: 10px; width: 100%; text-align: left; padding: 7px 10px; border: 0; background: transparent; color: var(--ink); font: 600 .95rem/1.3 var(--f-body); border-radius: 6px; cursor: pointer; text-decoration: none; }
.g-head:hover { background: var(--surface-2); }
.gi { display: inline-flex; flex: none; width: 18px; align-self: center; color: var(--ink-2); }
.gi .ico, .h-ico .ico, .card-ico .ico { display: block; width: 100%; height: 100%; fill: none; stroke: currentColor; }
.g-head.on .gi { color: var(--accent); }
.h-ico { display: inline-block; width: 24px; height: 24px; vertical-align: -3px; margin-right: 10px; color: var(--accent); }
.card-ico { display: block; width: 24px; height: 24px; margin-bottom: 14px; color: var(--accent); }
.g-head.on { color: var(--accent); }
.g ul { margin: 2px 0 8px 26px; border-left: 1px solid var(--line); display: none; }
.g.open ul { display: block; }
.g li a { display: block; padding: 5px 12px; color: var(--ink-2); text-decoration: none; border-radius: 0 6px 6px 0; }
.g li a:hover { color: var(--ink); background: var(--surface-2); }
.g li a[aria-current="page"] { color: var(--accent); background: var(--accent-soft); font-weight: 600; }
.doc { min-width: 0; }
.doc .eyebrow { margin-bottom: 12px; }
.doc h1 { font-size: clamp(1.9rem, 3.4vw, 2.6rem); line-height: 1.1; margin: 0 0 14px; font-weight: 600; }
.lede { font-size: 1.15rem; color: var(--ink-2); margin: 0 0 28px; max-width: 60ch; }
.spec-note { font: 400 .78rem/1.5 var(--f-mono); color: var(--ink-2); margin: 0 0 20px; }
.prose { max-width: 70ch; }
.prose p, .prose ul, .prose ol { margin: 0 0 1.05em; }
.prose h1 { font-size: clamp(1.7rem, 3vw, 2.2rem); margin: 0 0 .6em; }
.prose h2 { font-size: 1.55rem; line-height: 1.2; margin: 2em 0 .6em; font-weight: 600; scroll-margin-top: calc(var(--head-h) + 20px); }
.prose h3 { font-size: 1.2rem; margin: 1.7em 0 .5em; font-weight: 600; scroll-margin-top: calc(var(--head-h) + 20px); }
.prose h4 { font-size: 1.05rem; margin: 1.4em 0 .4em; }
.prose li { margin-bottom: .35em; }
.prose code { font: 400 .87em var(--f-mono); background: var(--surface-2); padding: .12em .38em; border-radius: 4px; }
.prose :not(pre) > code { overflow-wrap: anywhere; }
.prose pre { margin: 0; background: var(--surface-2); border: 1px solid var(--line); border-radius: 6px; padding: 14px 16px; font: 400 .84rem/1.55 var(--f-mono); white-space: pre; }
.prose pre code { background: none; padding: 0; font-size: inherit; }
.scroll { overflow-x: auto; margin: 0 0 1.2em; max-width: 100%; }
.prose table { border-collapse: collapse; font-size: .92rem; min-width: 100%; }
.prose th, .prose td { text-align: left; vertical-align: top; padding: 9px 12px; border-bottom: 1px solid var(--line); }
.prose th { font-weight: 600; background: var(--surface-2); white-space: nowrap; }
.prose blockquote { margin: 0 0 1em; padding-left: 16px; border-left: 3px solid var(--line); color: var(--ink-2); }
.prose hr { border: 0; border-top: 1px solid var(--line); margin: 2em 0; }
.prose pre.raw { white-space: pre-wrap; word-break: break-word; }
.pagenav { display: flex; gap: 16px; margin-top: 48px; padding-top: 24px; border-top: 1px solid var(--line); flex-wrap: wrap; }
.pagenav a { flex: 1 1 220px; border: 1px solid var(--line); border-radius: 8px; padding: 14px 18px; text-decoration: none; color: var(--ink); background: var(--surface); }
.pagenav a:hover { border-color: var(--accent); }
.pagenav small { display: block; color: var(--ink-2); font: 500 .72rem/1 var(--f-mono); text-transform: uppercase; letter-spacing: .08em; margin-bottom: 6px; }
.pagenav .next { text-align: right; }
.toc { position: sticky; top: calc(env(safe-area-inset-top, 0px) + var(--head-h) + 16px); font-size: .86rem; max-height: calc(100vh - var(--head-h) - 32px); overflow: auto; }
.toc h4 { font: 500 .72rem/1 var(--f-mono); text-transform: uppercase; letter-spacing: .08em; color: var(--ink-2); margin: 0 0 10px; }
.toc a { display: block; padding: 4px 0 4px 12px; color: var(--ink-2); text-decoration: none; border-left: 1px solid var(--line); }
.toc a:hover { color: var(--accent); border-left-color: var(--accent); }
.toc a.l3 { padding-left: 24px; }

/* simple pages */
.simple { max-width: 820px; padding-block: 48px 72px; }
.simple.wide { max-width: 1000px; }
.app-logo { display: inline-block; width: 36px; height: 36px; vertical-align: middle; margin-right: 10px; }
.app-logo img { display: block; width: 100%; height: 100%; border-radius: 9px; }
.simple.wide .prose { max-width: none; }
.simple.wide .prose p, .simple.wide .prose ul { max-width: 70ch; }
.simple.wide .prose td { white-space: nowrap; }
.prose td code, .prose td a { white-space: nowrap; }
.simple h1 { font-size: clamp(2rem, 4vw, 3rem); margin: 0 0 12px; font-weight: 600; line-height: 1.08; }

/* faq */
.faq-item { border-top: 1px solid var(--line); }
.faq-item:last-of-type { border-bottom: 1px solid var(--line); }
.faq-item summary { cursor: pointer; list-style: none; padding: 14px 32px 14px 0; font: 500 1.05rem/1.35 var(--f-display); position: relative; }
.faq-item summary::-webkit-details-marker { display: none; }
.faq-item summary::after { content: "+"; position: absolute; right: 4px; top: 12px; font: 400 1.4rem/1 var(--f-body); color: var(--ink-2); }
.faq-item[open] summary::after { content: "\2212"; }
.faq-item .a { padding: 0 0 16px; color: var(--ink); }
.faq-tools { display: flex; gap: 8px; margin: 0 0 12px; }

/* review helpers */
.chip-ph { font: 400 .85em var(--f-mono); color: var(--ink-2); border: 1px dashed var(--line); border-radius: 4px; padding: 0 6px; background: var(--surface); }
p.placeholder { border: 1px dashed var(--line); border-radius: 6px; padding: 10px 14px; color: var(--ink-2); background: var(--surface); }
a.stub { color: var(--ink-2); text-decoration: underline dotted; cursor: not-allowed; }
a.cta { font-weight: 600; }
.cta-row { display: flex; gap: 12px; flex-wrap: wrap; margin: 0 0 1.05em; }

@media (max-width: 1100px) {
  .docs { grid-template-columns: 250px minmax(0, 1fr); }
  .toc { display: none; }
}
@media (max-width: 860px) {
  .hero-grid, .split, .stay { grid-template-columns: minmax(0, 1fr); gap: 28px; }
  .beat { grid-template-columns: minmax(0, 1fr); gap: 10px; padding: 22px 0; }
  .cards, .changes, .status, .start { grid-template-columns: minmax(0, 1fr); }
  .docs { grid-template-columns: minmax(0, 1fr); gap: 16px; padding-block: 16px 56px; }
  .side { position: static; max-height: none; border: 1px solid var(--line); border-radius: 8px; background: var(--surface); padding: 4px 8px; }
  .side > summary { display: block; cursor: pointer; padding: 10px; font-weight: 600; }
  .tools { margin-left: 0; width: 100%; }
  .nav { margin-left: 0; }
  .hero { padding-block: 32px 24px; }
  .band { padding-block: 40px; }
}