/* Layout: a single reading column at paper measure, a left index rail and a right
   margin for annotations, like a well-read copy of the PDF. Figures span both columns. */
:root {
  --paper: #fbfbf9;
  --ink: #1a1b1e;
  --ink-2: #4a4c52;
  --mute: #7d8087;
  --rule: #e3e3df;
  --wash: #f2f2ee;
  --accent: #c76d12;
  --accent-wash: #f6ebdf;
  --bad: #b5402f;

  --serif: "Newsreader", "Iowan Old Style", "Palatino Linotype", Georgia, serif;
  --sans: "IBM Plex Sans", "Helvetica Neue", Arial, sans-serif;
  --mono: "IBM Plex Mono", ui-monospace, "SF Mono", Menlo, Consolas, monospace;

  --measure: 38rem;
  --margin: 15rem;
  --gap: 2.5rem;
  --header-h: 52px;
}
@media (prefers-color-scheme: dark) {
  :root:not([data-theme="light"]) {
    --paper: #121315; --ink: #e5e5e1; --ink-2: #b9bab6; --mute: #8a8c92; --rule: #2a2c30;
    --wash: #1a1b1e; --accent: #e3984a; --accent-wash: #2c2116; --bad: #e07462; color-scheme: dark;
  }
}
:root[data-theme="dark"] {
  --paper: #121315; --ink: #e5e5e1; --ink-2: #b9bab6; --mute: #8a8c92; --rule: #2a2c30;
  --wash: #1a1b1e; --accent: #e3984a; --accent-wash: #2c2116; --bad: #e07462; color-scheme: dark;
}

* { box-sizing: border-box; }
html { scroll-behavior: smooth; scroll-padding-top: calc(var(--header-h) + 24px); -webkit-text-size-adjust: 100%; }
@media (prefers-reduced-motion: reduce) { html { scroll-behavior: auto; } }
body {
  margin: 0; background: var(--paper); color: var(--ink);
  font-family: var(--serif); font-size: 1.125rem; line-height: 1.62;
  font-optical-sizing: auto; text-rendering: optimizeLegibility;
}
a { color: inherit; text-decoration-color: var(--rule); text-underline-offset: 3px; }
a:hover { text-decoration-color: var(--accent); }
:focus-visible { outline: 2px solid var(--accent); outline-offset: 2px; border-radius: 2px; }
button { font: inherit; color: inherit; }

/* ---------- top bar ---------- */
.bar {
  position: fixed; top: 0; left: 0; right: 0; z-index: 20;
  padding-top: env(safe-area-inset-top, 0px);
  background: color-mix(in srgb, var(--paper) 88%, transparent);
  backdrop-filter: saturate(1.2) blur(10px); -webkit-backdrop-filter: saturate(1.2) blur(10px);
  border-bottom: 1px solid var(--rule);
}
.bar-in {
  height: var(--header-h); display: flex; align-items: center; gap: 1rem;
  padding-inline: 16px; max-width: 86rem; margin: 0 auto;
}
.mark { font-family: var(--mono); font-size: .78rem; letter-spacing: .02em; color: var(--ink-2); text-decoration: none; white-space: nowrap; overflow: hidden; text-overflow: ellipsis; min-width: 0; }
.mark b { color: var(--ink); font-weight: 500; }
.bar-tools { margin-left: auto; display: flex; align-items: center; gap: .25rem; flex-shrink: 0; }
.chip {
  border: 0; background: none; cursor: pointer; font-family: var(--mono); font-size: .72rem;
  letter-spacing: .06em; text-transform: uppercase; color: var(--mute); padding: .45rem .5rem; border-radius: 4px;
}
.chip:hover { color: var(--ink); background: var(--wash); }
.chip[aria-pressed="true"] { color: var(--ink); }
.chip[aria-pressed="true"]::after { content: ""; display: block; height: 1px; background: var(--accent); margin-top: 2px; }
.sep { width: 1px; height: 18px; background: var(--rule); margin-inline: .35rem; }
.icon-btn { border: 0; background: none; cursor: pointer; width: 34px; height: 34px; display: grid; place-items: center; border-radius: 4px; color: var(--ink-2); }
.icon-btn:hover { background: var(--wash); color: var(--ink); }
.icon-btn svg { width: 17px; height: 17px; }
.icon-btn[aria-pressed="false"] { color: var(--mute); opacity: .7; }
.progress { position: absolute; left: 0; bottom: -1px; height: 1px; width: 100%; background: var(--accent); transform-origin: 0 50%; transform: scaleX(0); }
.toc-btn { display: none; }

/* ---------- page grid ---------- */
.page {
  max-width: 86rem; margin: 0 auto; padding-inline: 16px;
  padding-block: calc(var(--header-h) + 3.5rem) 4rem;
  display: grid; grid-template-columns: minmax(0, 1fr);
}
.rail { display: none; }
.doc { min-width: 0; width: 100%; max-width: var(--measure); margin: 0 auto; }

@media (min-width: 1180px) {
  .page { grid-template-columns: 12.5rem minmax(0, 1fr); column-gap: 3rem; }
  .rail { display: block; }
  .doc { margin: 0; max-width: calc(var(--measure) + var(--gap) + var(--margin)); padding-right: calc(var(--gap) + var(--margin)); }
  .notes-off .doc { padding-right: 0; max-width: var(--measure); margin-inline: auto 0; }
}
@media (min-width: 1400px) { .page { column-gap: 5rem; } }

/* ---------- index rail ---------- */
.rail-in { position: sticky; top: calc(var(--header-h) + 3.5rem); max-height: calc(100vh - var(--header-h) - 5rem); overflow: auto; }
.rail h2, .sheet h2 { font: 500 .68rem/1 var(--mono); letter-spacing: .12em; text-transform: uppercase; color: var(--mute); margin: 0 0 1rem; }
.toc { list-style: none; margin: 0; padding: 0; display: grid; gap: .1rem; }
.toc a {
  display: grid; grid-template-columns: 1.6rem 1fr; align-items: baseline;
  font-family: var(--sans); font-size: .8rem; line-height: 1.35; color: var(--mute); text-decoration: none;
  padding: .32rem 0; border-left: 1px solid var(--rule); padding-left: .75rem; transition: color .2s, border-color .2s;
}
.toc a span:first-child { font-family: var(--mono); font-size: .7rem; }
.toc a:hover { color: var(--ink); }
.toc a.on { color: var(--ink); border-left-color: var(--accent); }

/* ---------- title block (set like the paper: centred) ---------- */
.titleblock, .doc .titleblock p { text-align: center; }
.titleblock { margin: 0 auto 3.25rem; max-width: var(--measure); }
.eyebrow { font: 400 .72rem/1 var(--mono); letter-spacing: .14em; text-transform: uppercase; color: var(--mute); margin: 0 0 1.75rem; }
.titleblock h1 {
  font-family: var(--serif); font-weight: 500; font-size: clamp(2rem, 1.2rem + 3.4vw, 3.25rem);
  line-height: 1.08; letter-spacing: -.015em; margin: 0 auto 1.6rem; text-wrap: balance; max-width: 15em;
}
.author { font-size: 1.125rem; margin: 0; }
.author-meta { font: .76rem/1.7 var(--mono); color: var(--mute); margin: .35rem 0 0; }
.credit { font: .74rem/1.6 var(--sans); color: var(--mute); margin: 1.25rem 0 0; }

.abstract { margin: 0 auto 3.5rem; max-width: 34rem; font-size: 1.02rem; line-height: 1.6; color: var(--ink-2); position: relative; }
.abstract b { color: var(--ink); font-weight: 600; }

/* ---------- sections ---------- */
section.sec { margin: 0 0 3.25rem; }
.sec h2 {
  font-family: var(--serif); font-weight: 600; font-size: 1.45rem; line-height: 1.25; margin: 0 0 1.1rem;
  display: flex; gap: .75rem; align-items: baseline; text-wrap: balance;
}
.sec h2 .num { font: 400 .8rem/1 var(--mono); color: var(--accent); min-width: 1.6rem; }
.sec h2 a { text-decoration: none; }
.blk { position: relative; }
.blk + .blk { margin-top: 1.05rem; }
p { margin: 0; hyphens: auto; -webkit-hyphens: auto; }
.doc p, .doc li { text-align: justify; text-justify: inter-word; }
@media (max-width: 560px) { .doc p, .doc li { text-align: left; } }
em { font-style: italic; }
ol.steps { margin: 0; padding: 0; list-style: none; counter-reset: s; display: grid; gap: .45rem; }
ol.steps li { counter-increment: s; display: grid; grid-template-columns: 2rem 1fr; }
ol.steps li::before { content: counter(s) ")"; font-family: var(--mono); font-size: .85rem; color: var(--mute); padding-top: .2rem; }
.defs { margin: 0; display: grid; gap: .3rem; font-size: 1rem; }
.defs div { display: grid; grid-template-columns: 2.6rem 1fr; }
.defs dt { font-style: italic; }
.defs dd { margin: 0; }

/* ---------- margin notes ---------- */
.anc { text-decoration: underline dotted var(--accent); text-underline-offset: 4px; text-decoration-thickness: 1px; }
.nref { font: 500 .62rem/0 var(--mono); color: var(--accent); vertical-align: super; margin-left: 1px; cursor: pointer; user-select: none; }
.note { font-family: var(--sans); font-size: .8rem; line-height: 1.5; color: var(--ink-2); }
.note-h {
  display: flex; gap: .5rem; align-items: baseline; width: 100%; text-align: left; border: 0; background: none; padding: 0;
  font: 600 .8rem/1.35 var(--sans); color: var(--ink); cursor: pointer;
}
.note-h .k { font: 500 .62rem/1 var(--mono); color: var(--accent); flex-shrink: 0; }
.note-b { margin: .35rem 0 0; }
.note-b p { text-align: left; hyphens: manual; }

@media (min-width: 1180px) {
  .note {
    position: absolute; top: .2rem; left: calc(100% + var(--gap)); width: var(--margin);
    padding-left: .85rem; border-left: 1px solid var(--rule); transition: border-color .25s, color .25s;
  }
  .note-h { cursor: default; pointer-events: none; }
  .note-b[hidden] { display: block !important; }
  .blk:hover .note, .note.hot { border-left-color: var(--accent); color: var(--ink); }
  .notes-off .note { display: none; }
}
@media (max-width: 1179px) {
  .note { margin-top: .85rem; padding: .7rem .9rem; background: var(--wash); border-radius: 6px; }
  .note-h::after { content: "+"; margin-left: auto; font: 400 .9rem/1 var(--mono); color: var(--mute); }
  .note-h[aria-expanded="true"]::after { content: "–"; }
  .notes-off .note, .notes-off .nref { display: none; }
}

/* ---------- figures ---------- */
.fig { margin: 2.1rem 0 2.25rem; }
@media (min-width: 1180px) { .fig { margin-right: calc(-1 * (var(--gap) + var(--margin))); } .notes-off .fig { margin-right: 0; } }
.fig-frame { border-top: 1px solid var(--rule); border-bottom: 1px solid var(--rule); padding: 1.5rem 0 1.1rem; }
.fig-scroll { overflow-x: auto; -webkit-overflow-scrolling: touch; }
.fig svg { display: block; width: 100%; height: auto; min-width: 620px; margin: 0 auto; overflow: visible; }
.fig svg.narrow-ok { min-width: 0; }
.fig-foot { display: flex; flex-wrap: wrap; align-items: center; gap: .6rem 1rem; margin-top: .9rem; font: .75rem/1.5 var(--sans); color: var(--mute); }
.fig-foot .tag { font: 500 .64rem/1 var(--mono); letter-spacing: .12em; text-transform: uppercase; color: var(--mute); }
.fig-foot .say { flex: 1 1 16rem; min-width: 0; }
.fig-foot .say b { color: var(--ink); font-weight: 500; }
.ctrls { display: flex; flex-wrap: wrap; gap: .4rem; margin-left: auto; }
.btn {
  border: 1px solid var(--rule); background: var(--paper); border-radius: 999px; padding: .32rem .8rem; cursor: pointer;
  font: 500 .72rem/1.2 var(--mono); letter-spacing: .03em; color: var(--ink-2); transition: border-color .2s, color .2s, background .2s;
}
.btn:hover { border-color: var(--ink-2); color: var(--ink); }
.btn[aria-pressed="true"] { border-color: var(--accent); color: var(--ink); background: var(--accent-wash); }
.btn:disabled { opacity: .5; cursor: default; }

/* SVG vocabulary */
.s-box { fill: var(--paper); stroke: var(--ink-2); stroke-width: 1; }
.s-box.soft { stroke: var(--rule); fill: var(--wash); }
.s-box.ghost { stroke: var(--rule); stroke-dasharray: 3 3; fill: none; }
.s-line { stroke: var(--ink-2); stroke-width: 1; fill: none; }
.s-line.faint { stroke: var(--rule); }
.s-txt { fill: var(--ink); font-family: var(--sans); font-size: 11px; }
.s-txt.m { font-family: var(--mono); font-size: 10px; fill: var(--ink-2); }
.s-txt.mute { fill: var(--mute); }
.s-txt.cap { font-size: 10.5px; fill: var(--mute); }
.s-txt.h { font-weight: 600; font-size: 11.5px; }
.s-arrow { fill: var(--ink-2); }
.hot .s-box, .s-box.hot { stroke: var(--accent); stroke-width: 1.5; fill: var(--accent-wash); }
.s-line.hot { stroke: var(--accent); stroke-width: 1.5; }
.s-txt.hot { fill: var(--accent); }
.s-dot { fill: var(--accent); }
.anim { transition: opacity .5s ease, stroke .3s, fill .3s, stroke-width .3s; }
.fade { opacity: .12; }
@media (prefers-reduced-motion: reduce) { .anim { transition: none; } }

/* proof-of-work cards */
.pow { display: grid; grid-template-columns: repeat(3, minmax(13.5rem, 1fr)); gap: 0; align-items: stretch; min-width: 0; }
.pow-wrap { overflow-x: auto; padding-bottom: .25rem; }
.pblock { position: relative; border: 1px solid var(--ink-2); border-radius: 3px; padding: .85rem .9rem .8rem; font-family: var(--mono); font-size: .72rem; background: var(--paper); transition: border-color .3s, background .3s; min-width: 0; }
.pblock + .pblock { margin-left: 2.4rem; }
.pblock + .pblock::before { content: ""; position: absolute; left: -2.4rem; top: 2.15rem; width: 2.4rem; border-top: 1px solid var(--ink-2); }
.pblock + .pblock::after { content: ""; position: absolute; left: -7px; top: calc(2.15rem - 4px); border: 4px solid transparent; border-left: 6px solid var(--ink-2); }
.pblock.bad { border-color: var(--bad); border-style: dashed; }
.pblock .ph { display: flex; justify-content: space-between; align-items: baseline; font: 600 .78rem/1 var(--sans); margin-bottom: .7rem; }
.pblock .st { font: 500 .62rem/1 var(--mono); letter-spacing: .04em; color: var(--mute); display: flex; gap: .35rem; align-items: center; }
.pblock .st::before { content: ""; width: 6px; height: 6px; border-radius: 50%; background: var(--accent); }
.pblock.bad .st { color: var(--bad); }
.pblock.bad .st::before { background: var(--bad); }
.prow { display: grid; grid-template-columns: 4.6rem minmax(0, 1fr); gap: .5rem; padding: .28rem 0; border-top: 1px solid var(--rule); align-items: baseline; }
.prow > span:first-child { color: var(--mute); font-family: var(--sans); font-size: .68rem; }
.prow .hx { overflow-wrap: anywhere; color: var(--ink-2); line-height: 1.35; }
.prow .hx i { font-style: normal; color: var(--accent); }
.pblock.bad .prow .hx.self i { color: var(--bad); }
.prow input {
  width: 100%; min-width: 0; font: inherit; color: var(--ink); background: var(--wash); border: 1px solid transparent; border-radius: 3px; padding: .2rem .35rem;
}
.prow input:focus { outline: none; border-color: var(--accent); background: var(--paper); }
.pblock .mine { margin-top: .6rem; width: 100%; }
@media (max-width: 760px) {
  .pow { grid-template-columns: minmax(0, 1fr); }
  .pblock + .pblock { margin-left: 0; margin-top: 1.9rem; }
  .pblock + .pblock::before { left: 50%; top: -1.9rem; width: 0; height: 1.9rem; border-top: 0; border-left: 1px solid var(--ink-2); }
  .pblock + .pblock::after { left: calc(50% - 4px); top: -7px; border: 4px solid transparent; border-top: 6px solid var(--ink-2); }
}

/* calculation chart */
.calc-top { display: flex; flex-wrap: wrap; gap: .75rem 1.5rem; align-items: center; margin-bottom: 1rem; }
.calc-top label { font: .78rem/1.3 var(--sans); color: var(--ink-2); display: flex; align-items: center; gap: .75rem; flex: 1 1 18rem; }
.calc-top output { font: 500 .9rem/1 var(--mono); color: var(--accent); min-width: 3.2rem; font-variant-numeric: tabular-nums; }
input[type="range"] { flex: 1; min-width: 8rem; accent-color: var(--accent); }
.calc-say { font: .85rem/1.5 var(--sans); color: var(--ink); margin: .2rem 0 0; }
.calc-say b { font-family: var(--mono); font-weight: 500; color: var(--accent); }

/* math and code */
.math { margin: 1.6rem 0; overflow-x: auto; padding: .25rem 0; }
.math math { font-size: 1.15rem; font-family: "STIX Two Math", "Cambria Math", "Latin Modern Math", var(--serif); }
pre.code, .tbl {
  font: .8rem/1.6 var(--mono); color: var(--ink-2); background: var(--wash); border-radius: 4px;
  padding: 1rem 1.1rem; margin: 1.4rem 0; overflow-x: auto; tab-size: 4;
}
pre.code .kw { color: var(--accent); }
pre.code .cm { color: var(--mute); }
.tbls { display: flex; flex-wrap: wrap; gap: 1rem 2.5rem; }
.tbl { display: inline-grid; grid-template-columns: auto auto; column-gap: 1.6rem; margin: 0; font-variant-numeric: tabular-nums; }
.tbl .th { grid-column: 1 / -1; color: var(--ink); margin-bottom: .2rem; }

/* references and footer */
.refs { margin-top: 4rem; padding-top: 2rem; border-top: 1px solid var(--rule); }
.refs h2 { font: 500 .68rem/1 var(--mono); letter-spacing: .12em; text-transform: uppercase; color: var(--mute); margin: 0 0 1.25rem; }
.refs ol { list-style: none; margin: 0; padding: 0; display: grid; gap: .55rem; font-size: .9rem; line-height: 1.5; color: var(--ink-2); }
.refs li { display: grid; grid-template-columns: 2rem minmax(0, 1fr); overflow-wrap: anywhere; text-align: left !important; }
.refs li span:first-child { font-family: var(--mono); font-size: .75rem; color: var(--mute); padding-top: .15rem; }
.colophon { margin-top: 3rem; font: .76rem/1.6 var(--sans); color: var(--mute); display: grid; gap: .45rem; }
.colophon p { text-align: left !important; }

/* mobile index sheet */
.sheet { position: fixed; inset: 0; z-index: 30; display: none; }
.sheet.open { display: block; }
.sheet .scrim { position: absolute; inset: 0; background: color-mix(in srgb, var(--ink) 25%, transparent); }
.sheet .panel {
  position: absolute; left: 0; right: 0; bottom: 0; max-height: 78vh; overflow: auto; background: var(--paper);
  border-top: 1px solid var(--rule); border-radius: 12px 12px 0 0; padding: 1.4rem 16px calc(1.4rem + env(safe-area-inset-bottom, 0px));
}
@media (max-width: 1179px) { .toc-btn { display: grid; } }
@media (max-width: 520px) { .mark .long { display: none; } .chip { padding: .45rem .34rem; } .sep { margin-inline: .15rem; } }

/* gentle entrance; content is visible at rest */
@media (prefers-reduced-motion: no-preference) {
  .rise { animation: rise .7s cubic-bezier(.2,.7,.2,1) both; }
  @keyframes rise { from { opacity: .001; transform: translateY(6px); } to { opacity: 1; transform: none; } }
}

/* flowing dash on active paths */
.s-line.flow { stroke-dasharray: 5 4; animation: flow 1.1s linear infinite; }
@keyframes flow { to { stroke-dashoffset: -18; } }
.cite { text-decoration: none; color: var(--mute); }
.cite:hover { color: var(--accent); }

/* language picker: native select (best on phones), styled to sit quietly in the bar */
.lang-sel { position: relative; display: inline-flex; align-items: center; gap: .4rem; height: 34px; padding: 0 .55rem; border-radius: 4px; color: var(--ink-2); cursor: pointer; }
.lang-sel:hover, .lang-sel:focus-within { background: var(--wash); color: var(--ink); }
.lang-sel svg { width: 16px; height: 16px; flex-shrink: 0; }
.lang-code { font: 500 .72rem/1 var(--mono); letter-spacing: .06em; text-transform: uppercase; }
.lang-code::after { content: ""; display: inline-block; margin-left: .35rem; width: 5px; height: 5px; border-right: 1px solid currentColor; border-bottom: 1px solid currentColor; transform: translateY(-2px) rotate(45deg); }
.lang-sel select { position: absolute; inset: 0; width: 100%; height: 100%; opacity: 0; cursor: pointer; font-size: 16px; }
.lang-sel:focus-within { outline: 2px solid var(--accent); outline-offset: 1px; }

/* per-script typography */
:root[lang="el"], :root[lang="ru"] { --serif: "Noto Serif", "Georgia", "Times New Roman", serif; }
:root[lang="ja"] { --serif: "Noto Serif JP", "Hiragino Mincho ProN", "Yu Mincho", serif; --sans: "Noto Sans JP", "Hiragino Sans", "Yu Gothic", sans-serif; }
:root[lang="ko"] { --serif: "Noto Serif KR", "AppleMyungjo", "Batang", serif; --sans: "Noto Sans KR", "Apple SD Gothic Neo", "Malgun Gothic", sans-serif; }
:root[lang="ja"] .doc p, :root[lang="ja"] .doc li, :root[lang="ko"] .doc p, :root[lang="ko"] .doc li { text-align: left; hyphens: none; }
:root[lang="ja"] .doc p, :root[lang="ja"] .doc li { line-break: strict; line-height: 1.85; }
:root[lang="ko"] .doc p, :root[lang="ko"] .doc li { word-break: keep-all; line-height: 1.8; }
:root[lang="ja"] em, :root[lang="ko"] em { font-style: normal; }
:root[lang="ja"] .titleblock h1, :root[lang="ko"] .titleblock h1 { letter-spacing: 0; line-height: 1.3; }

.made-by { margin-top: 1.25rem; padding-top: 1.25rem; border-top: 1px solid var(--rule); font: .78rem/1.5 var(--mono); letter-spacing: .02em; color: var(--mute); }
.made-by a, .made-by span { color: var(--ink); text-decoration: none; }
.made-by a:hover { color: var(--accent); }