/* ============================================================
   Beige Papers — styles-v3
   A house style for self-published intellectual work.

   Tone: unpretentious but exacting. The "beige" is a wink —
   these aren't whitepapers — but the typography is not joking.
   Flat edges, hairline rules, a warm paper ground, one accent.

   IMPORTANT: the math-rendering JS (lib/traction-interpret.js)
   emits a fixed class contract. Everything under
   "MATH EXPRESSIONS" preserves that contract verbatim — restyle
   with care. Everything above it is document chrome and is free
   to change.
   ============================================================ */

/* ---------- Design tokens ---------- */
:root {
    --paper:       #f6f2e9;   /* warm ground — the "beige", dialed way back */
    --paper-edge:  #efe9db;   /* faint panel tint for asides */
    --ink:         #23201b;   /* near-black, slightly warm */
    --ink-soft:    #6b6455;   /* muted captions / metadata */
    --rule:        #cdc4b0;   /* hairline dividers */
    --rule-bold:   #23201b;   /* heavy rules under titles */
    --accent:      #9a3324;   /* oxblood — links, marks, flourish */
    --accent-deep: #6f2318;   /* hover / pressed */
    --code-bg:     #262320;
    --code-fg:     #d9d2c3;

    --measure:     42rem;     /* comfortable reading width */
    --leading:     1.62;

    --font-display: "Fraunces", "IBM Plex Serif", Georgia, serif;
    --font-body:    "Newsreader", "IBM Plex Serif", Georgia, serif;
    --font-meta:    "IBM Plex Mono", ui-monospace, monospace;
    --font-code:    "IBM Plex Mono", ui-monospace, monospace;
    --font-math:    "STIX Two Text", "Cambria Math", "Latin Modern Math", serif;
    --font-mathsym: "Libertinus Math", system-ui;
}

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

html {
    /* subtle paper texture: two barely-there tints, no image needed */
    background-color: #ece5d6;
    -webkit-text-size-adjust: 100%;
}

body {
    font-family: var(--font-body);
    font-optical-sizing: auto;
    font-size: 1.125rem;
    line-height: var(--leading);
    color: var(--ink);
    background-color: var(--paper);
    max-width: var(--measure);
    margin: 0 auto;
    padding: 4.5rem 1.5rem 8rem;
    /* one continuous sheet, flat-edged, sitting on the darker backdrop */
    border-left: 1px solid var(--rule);
    border-right: 1px solid var(--rule);
    text-rendering: optimizeLegibility;
    -webkit-font-smoothing: antialiased;
}

p {
    margin: 0 0 1.15rem;
    hanging-punctuation: first;
}

/* ---------- Headings ---------- */
h1, h2, h3, h4 {
    font-family: var(--font-display);
    font-optical-sizing: auto;
    color: var(--ink);
    line-height: 1.12;
    text-wrap: balance;
}

h1 {
    font-weight: 600;
    font-size: 3rem;
    letter-spacing: -0.02em;
    text-align: center;
    margin: 0 0 0.15em;
}

h2 {
    font-weight: 380;
    font-style: italic;
    font-size: 1.4rem;
    color: var(--ink-soft);
    text-align: center;
    letter-spacing: 0.01em;
    margin: 0 0 1.5em;
}

h3 {
    font-weight: 560;
    font-size: 1.55rem;
    letter-spacing: -0.01em;
    margin: 2.4em 0 0.6em;
}

h4 {
    font-weight: 560;
    font-size: 1.15rem;
    margin: 2em 0 0.5em;
}

/* ---------- Masthead ---------- */
.headings {
    padding: 0 0 1.4rem;
    margin: 0 0 2.6rem;
    border-bottom: 2px solid var(--rule-bold);
}

/* wry little wordmark option: use on the index masthead */
.headings h1 .stamp {
    display: inline-block;
    font-family: var(--font-meta);
    font-size: 0.8rem;
    font-weight: 400;
    letter-spacing: 0.18em;
    text-transform: uppercase;
    color: var(--accent);
    vertical-align: middle;
}

/* ---------- Sections (flat, no cards) ---------- */
.section {
    margin: 0 0 3.5rem;
    padding: 0;
    background: none;
    border: none;
    border-radius: 0;
    box-shadow: none;
    break-inside: avoid;
}

.section-title {
    font-family: var(--font-display);
    font-weight: 560;
    font-size: 1.55rem;
    letter-spacing: -0.01em;
    margin: 0 0 1.1rem;
    padding: 0 0 0.4rem;
    border-bottom: 1px solid var(--rule);
}

.subsection-title {
    font-family: var(--font-display);
    font-weight: 560;
    font-size: 1.2rem;
    margin: 2em 0 0.8em;
    padding: 0;
    border: none;
}

.section-footer {
    margin: 2rem 0 0;
    padding: 0.9rem 0 0;
    border-top: 1px solid var(--rule);
    font-family: var(--font-meta);
    font-size: 0.78rem;
    letter-spacing: 0.02em;
    color: var(--ink-soft);
}

.emphasis { font-weight: 600; }

/* ---------- Aside / callout ---------- */
.section-alt {
    margin: 2rem 0;
    padding: 1.25rem 1.5rem;
    background-color: var(--paper-edge);
    border: none;
    border-left: 3px solid var(--accent);
    border-radius: 0;
    font-size: 0.98em;
}
.section-alt > :last-child { margin-bottom: 0; }

/* ---------- Links ---------- */
a, a:active, a:target {
    color: var(--accent);
    text-decoration: none;
    text-decoration-color: var(--rule);
    text-underline-offset: 0.14em;
    border-bottom: 1px solid color-mix(in srgb, var(--accent) 35%, transparent);
    transition: color 0.12s ease, border-color 0.12s ease;
}
a:hover, a:focus {
    color: var(--accent-deep);
    border-bottom-color: var(--accent-deep);
}

/* ---------- Lists ---------- */
ul, ol { padding-left: 1.4rem; }
li { margin: 0.5rem 0; }

/* Index / table-of-contents lists: give each entry a title + blurb */
ul li > a { font-weight: 500; }
ul li > div,
ol li > div {
    color: var(--ink-soft);
    font-size: 0.94em;
    line-height: 1.5;
    margin: 0.15rem 0 0;
}
/* an <i> title = "planned but unpublished" */
ul li > i {
    color: var(--ink-soft);
    font-style: italic;
}

/* ---------- Tables ---------- */
table {
    font-family: var(--font-body);
    border-collapse: collapse;
    width: 100%;
    margin: 1.8rem 0;
    font-size: 0.98rem;
}
table.fixed { table-layout: fixed; width: 100%; }
caption {
    caption-side: bottom;
    font-family: var(--font-meta);
    font-size: 0.78rem;
    color: var(--ink-soft);
    padding-top: 0.6rem;
    text-align: left;
}
tr { border: none; }
th {
    font-family: var(--font-display);
    font-weight: 560;
    text-align: left;
    padding: 0.45rem 0.7rem;
    border-bottom: 2px solid var(--rule-bold);
}
td {
    padding: 0.4rem 0.7rem;
    border-bottom: 1px solid var(--rule);
}
table.centered td, table.centered th { text-align: center; }
table .expression { margin: 0.6em 0.1em; }

/* ---------- Figures & images ---------- */
figure { margin: 2.2rem 0; }
figcaption {
    font-family: var(--font-meta);
    font-size: 0.78rem;
    color: var(--ink-soft);
    margin-top: 0.6rem;
}
img.fullsize-image {
    width: 100%;
    height: auto;
    display: block;
    background-size: cover;
}
.big-image-border {
    border: 1px solid var(--rule-bold);
    margin: 2.2rem 0;
}
.big-image-border img.fullsize-image { display: block; }
.fullsize-image-dark {
    width: 100%;
    background-color: #222;
    border: 1px solid var(--rule-bold);
}
.fullsize-image-dark img { max-width: 100%; display: block; }

/* ---------- Utilities ---------- */
.centered { text-align: center; }
.w50 { width: 50%; }
.font-lg { font-size: 1.5em; }
.font-xl { font-size: 2em; }
.color-inv { color: var(--paper); background-color: var(--ink); }

canvas { image-rendering: auto; }

.icon-back {
    width: 2em;
    position: absolute;
    aspect-ratio: 1/1;
    background-size: contain;
    background-position: center;
    background-repeat: no-repeat;
    background-image: url(./img/back-icon.png);
    cursor: pointer;
    opacity: 0.7;
}
.icon-back:hover { opacity: 1; }

/* ============================================================
   MATH EXPRESSIONS  — class contract from traction-interpret.js
   Preserve structure; only colors/fonts routed through tokens.
   ============================================================ */

.expression, .expression-inline {
    font-family: var(--font-math);
    font-size: 1.2em;
    margin: 1rem;
    white-space: nowrap;
}
.expression-inline { margin: 0; }

/* The interpreter emits <wbr> break-hints after +/- so LONG inline expressions
   can wrap at term boundaries. But <wbr> breaks even under white-space:nowrap,
   which must never happen inside an atomic unit (a fraction, root, or its
   radicand) or inside a centered display equation — a split there breaks the
   fraction bar / radical overbar. Suppress the hint in exactly those places. */
.expression wbr,
.fraction wbr,
.sqrt wbr,
.radicand wbr,
sup wbr,
sub wbr { display: none; }

.expression sup { padding-right: 0.2em; }
.expression-inline sup { padding-right: 0.35em; }

.expr-label {
    display: inline;
    font-weight: bold;
    padding-right: 1em;
    font-size: 1.2rem;
    font-family: var(--font-display);
}

sup {
    display: inline-block;
    position: relative;
    top: -0.1em;
    line-height: 1;
    font-size: 0.8em;
}
sup.smaller { font-size: 0.65em; }
sup.smaller sup.smaller { font-size: 0.9em; }
sup.smaller sub.smaller { font-size: 0.9em; }

sub {
    display: inline-block;
    position: relative;
    bottom: -0.1em;
    line-height: 1;
    font-size: 0.9em;
}
sub.smaller { font-size: 0.6em; }

span.variable, span.symbol, span.number, sup, sub, .fraction {
    white-space: nowrap;
}

.variable {
    font-family: var(--font-math);
    font-style: italic;
    margin: 0.1em;
}
.symbol {
    font-family: var(--font-mathsym);
    display: inline;
    margin: 0.1em;
}
.symbol.stretch { display: inline-block; transform: scaleY(2); }
.symbol.italics { font-style: italic; }
.symbol.invisible { position: absolute; color: rgba(1,1,1,50%); }

.fraction {
    display: inline-flex;
    flex-direction: column;
    vertical-align: middle;
    margin: 0 0.1em;
    font-size: 0.75em;
}
sup .fraction, .sqrt .fraction, .nostack .fraction { display: inline; margin: 0; }
p .fraction { margin: 0 0.2em; font-size: 0.8em; }

.numerator { display: inline; vertical-align: middle; align-self: center; }
.denominator { display: inline; vertical-align: middle; align-self: center; padding-top: 1px; }

.h-divider {
    display: inline;
    height: 1px;
    border-top: 1px solid var(--ink);  /* the visible bar — an explicit color, */
    color: transparent;                /* while the copyable "/" text stays hidden */
    white-space: nowrap;
}
sup .h-divider, .sqrt .h-divider, .nostack .h-divider {
    height: auto;
    border: none;
    color: inherit;
}

.parens-group {
    margin: 0 -0.4em;
    display: inline-flex;
    flex-direction: row;
    align-items: center;
}
.parens-group > .parens-content { display: flex; }

.sqrt { font-family: var(--font-mathsym); }
.sqrt .radicand {
    font-family: var(--font-math);
    border-top: 0.07em solid currentColor;
    padding-top: 0.11em;
    margin-left: -0.18em;
}

.narration sup { margin-right: -0.2em; display: inline; }

/* ---- Plain-text copy channels -----------------------------------
   Two complementary primitives keep a copied formula re-parseable:

   .copyonly   — IN the clipboard, INVISIBLE on screen. Real text kept
                 in the DOM but pulled out of flow (used for ^, _, and
                 grouping parens the eye doesn't need but the parser does).

   .op-*       — the reverse: pretty operator ON screen via ::before
                 (generated content is never copied), with the ASCII the
                 grammar expects carried in a nested .copyonly. So the
                 screen shows  x − 4 · √y  while the clipboard gets the
                 round-trippable  x-4*sqrt(y).
   ------------------------------------------------------------------ */
.copyonly {
    position: absolute;
    opacity: 0;
    padding: 0;
    margin: 0;
    width: 0;
    height: 0;
}

.op-minus::before { content: "\2212"; }  /* − true minus, not a hyphen */
.op-times::before { content: "\00B7"; }  /* · middle dot */
.op-pm::before    { content: "\00B1"; }  /* ± unary "+-", or binary "(+/-)" */
.op-radic::before { content: "\221A"; }  /* √ (copies as "sqrt(…)") */

/* Explicit parenthesised operators — glyph here, "(TOK)" in the copy stream. */
.op-mp::before        { content: "\2213"; }  /* ∓  (-/+) */
.op-cross::before     { content: "\00D7"; }  /* ×  (><) cross product */
.op-le::before        { content: "\2264"; }  /* ≤  bare <= =< */
.op-ge::before        { content: "\2265"; }  /* ≥  bare >= */
.op-dimplies::before  { content: "\21D2"; }  /* ⇒  (=>) */
.op-dimpliedby::before{ content: "\21D0"; }  /* ⇐  (<=) */
.op-iff::before       { content: "\21D4"; }  /* ⇔  (<=>) */
.op-oplus::before     { content: "\2295"; }  /* ⊕  (+) harmonic addition */
.op-def::before       { content: "\2254"; }  /* ≔  :=  definition */

.tiny-error {
    display: inline-block;
    font-family: var(--font-code);
    white-space-collapse: preserve;
    background-color: var(--paper);
    color: var(--accent);
    font-size: 0.5em;
    min-width: 0;
    padding: 0.2em;
    border: 1px solid var(--accent);
}

/* ============================================================
   CODE
   ============================================================ */

span.code {
    font-family: var(--font-code);
    font-size: 0.92em;
    background: var(--paper-edge);
    padding: 0.05em 0.3em;
    border-radius: 2px;
}

.code-border { margin: 1.8rem 0; }

.code-title {
    background-color: var(--ink);
    color: var(--paper);
    font-family: var(--font-meta);
    font-size: 0.82rem;
    letter-spacing: 0.04em;
    padding: 0.5em 0.8em;
    margin: 0;
    display: flex;
    justify-content: space-between;
}
.code-title .rfloat { font-family: var(--font-meta); color: var(--rule); }

div.code {
    background-color: var(--code-bg);
    color: var(--code-fg);
    border: none;
    padding: 1em 0.9em;
    font-size: 0.9rem;
    line-height: 1.5;
    font-family: var(--font-code);
    white-space: pre;
    margin: 0;
    overflow-x: auto;
    position: relative;
}

/* SPN syntax highlighting — muted phosphor, no CRT gimmicks */
.spn-keyword { color: #c8a25a; font-weight: 600; }
.spn-ident   { color: #d9d2c3; }
.spn-number  { color: #9ec6a3; }
.spn-op      { color: #a89f8c; }
.spn-assign  { color: #e0b968; font-weight: 600; }
.spn-punct   { color: #857d6c; }
.spn-not     { color: #d3705f; }
.spn-error   { color: #d3705f; background: rgba(211,112,95,0.12); padding: 0 0.3em; }

/* ---------- Numbered nested lists ---------- */
ol.nested { list-style-type: none; counter-reset: level1; padding-left: 2em; }
ol.nested li { counter-increment: level1; position: relative; }
ol.nested > li::before {
    content: counter(level1) ". ";
    display: inline-block;
    width: 2em;
    margin-left: -2em;
    font-family: var(--font-meta);
    color: var(--ink-soft);
}
ol.nested > li > ol.nested { list-style-type: none; counter-reset: level2; }
ol.nested > li > ol.nested > li { counter-increment: level2; position: relative; }
ol.nested > li > ol.nested > li::before {
    content: counter(level1) "." counter(level2);
    display: inline-block;
    width: 2.5em;
    margin-left: -2.5em;
    font-family: var(--font-meta);
    color: var(--ink-soft);
}

/* ============================================================
   RESPONSIVE
   ============================================================ */
@media only screen and (max-width: 640px) {
    body {
        max-width: 100%;
        padding: 2.5rem 1.15rem 5rem;
        border-left: none;
        border-right: none;
        font-size: 1.06rem;
    }
    h1 { font-size: 2.2rem; }
    h2 { font-size: 1.2rem; }
    sup, sub { white-space: wrap; box-sizing: border-box; display: inline-block; }
    /* expressions stay nowrap at every width — they may overflow-scroll, but a
       term must never break across lines. Do not add white-space:normal here. */
    .expression { box-sizing: border-box; width: 100%; }
}

/* ============================================================
   PRINT  — the whole point: clean paper, no ink-wasting chrome
   ============================================================ */
@media print {
    html, body {
        background: #fff;
        color: #000;
        max-width: none;
        border: none;
        padding: 0;
        font-size: 11pt;
    }
    .section { break-inside: avoid; }
    .section-alt {
        background: none;
        border-left: 2px solid #000;
    }
    a, a:active, a:target, a:hover, a:focus {
        color: #000;
        border-bottom: none;
        text-decoration: none;
    }
    .color-inv {
        color: #000;
        background: #fff;
        border: 1px solid #000;
    }
    .icon-back { display: none; }
    div.code {
        background: none;
        color: #000;
        border: 1px solid #000;
    }
    div.code span, .code-title {
        background: none !important;
        color: #000 !important;
    }
    .spn-keyword, .spn-assign { font-weight: 700; }
}