/* Torus Engineering — paper-style stylesheet */

:root {
  --paper: #fdfdfc;
  --ink: #111111;
  --ink-soft: #444444;
  --ink-faint: #595959;
  --rule: #cccccc;
  --rule-dark: #111111;
}

* {
  box-sizing: border-box;
}

html {
  background: var(--paper);
}

body {
  margin: 0;
  color: var(--ink);
  background: var(--paper);
  font-family: "STIX Two Text", "Noto Serif JP", "Times New Roman", "Yu Mincho", serif;
  font-size: 1.05rem;
  line-height: 1.85;
  -webkit-text-size-adjust: 100%;
}

:lang(ja) {
  text-align: justify;
}

a {
  color: var(--ink);
  text-decoration: underline;
  text-underline-offset: 0.2em;
  text-decoration-color: #888888;
}

a:hover {
  text-decoration-color: var(--ink);
}

:focus-visible {
  outline: 2px solid var(--ink);
  outline-offset: 2px;
}

var,
.math {
  font-style: italic;
  font-family: "STIX Two Text", "Times New Roman", serif;
}

sup,
sub {
  line-height: 0;
  font-size: 0.72em;
}

/* ---- header ---- */

.site-header {
  max-width: 44rem;
  margin: 0 auto;
  padding: 1rem 1.25rem 0.6rem;
  display: flex;
  justify-content: space-between;
  align-items: baseline;
  gap: 1rem;
  font-size: 0.85rem;
  color: var(--ink-faint);
  border-bottom: 1px solid var(--rule);
}

.site-header .venue {
  font-style: italic;
  letter-spacing: 0.02em;
}

.lang-switch a {
  color: var(--ink);
}

.lang-switch [aria-current="true"] {
  font-weight: 600;
  text-decoration: none;
}

/* ---- layout ---- */

main {
  max-width: 44rem;
  margin: 0 auto;
  padding: 0 1.25rem 3rem;
}

/* ---- hero ---- */

.hero {
  text-align: center;
  padding-top: 2.75rem;
}

.hero h1 {
  font-size: clamp(2.1rem, 7vw, 3.2rem);
  font-weight: 500;
  letter-spacing: 0.01em;
  margin: 0;
  line-height: 1.2;
}

.hero .subtitle {
  margin: 0.35rem 0 0;
  font-size: 1.05rem;
  color: var(--ink-soft);
  letter-spacing: 0.25em;
}

.hero .catch {
  font-size: clamp(1.2rem, 4vw, 1.55rem);
  font-weight: 600;
  margin: 1.9rem 0 0.4rem;
}

.hero .catch:lang(en) {
  font-style: italic;
  font-weight: 500;
}

.hero .tagline {
  margin: 0;
  font-size: 0.98rem;
  color: var(--ink-faint);
}

.hero .authors {
  margin: 1.8rem 0 0;
  font-size: 0.95rem;
  font-variant: small-caps;
  letter-spacing: 0.06em;
  color: var(--ink-soft);
}

/* ---- abstract ---- */

.abstract {
  margin: 2.2rem auto 0;
  max-width: 36rem;
  font-size: 0.94rem;
  line-height: 1.8;
  text-align: justify;
}

.abstract .abstract-head {
  display: block;
  text-align: center;
  font-variant: small-caps;
  letter-spacing: 0.12em;
  font-weight: 600;
  margin-bottom: 0.4rem;
}

/* ---- figures ---- */

figure {
  margin: 2.5rem 0;
  text-align: center;
}

figure svg {
  max-width: 100%;
  height: auto;
}

figure.fig-hero svg {
  max-width: 34rem;
}

figure.fig-klein svg {
  max-width: 22rem;
}

figure.fig-fractal svg {
  max-width: 34rem;
}

figure.fig-surfaces svg {
  max-width: 100%;
}

figure.fig-bulk svg {
  max-width: 38rem;
}

figure.fig-blackhole svg {
  display: block;
  max-width: 34rem;
  margin: 0 auto;
}

figure.fig-hairy svg {
  display: block;
  max-width: 24rem;
  margin: 0 auto;
}

figcaption {
  font-size: 0.88rem;
  color: var(--ink-soft);
  max-width: 32rem;
  margin: 0.6rem auto 0;
  line-height: 1.7;
  text-align: center;
}

figcaption .fig-label {
  font-weight: 600;
}

/* ---- sections ---- */

section {
  margin-top: 3rem;
}

h2 {
  font-size: 1.25rem;
  font-weight: 600;
  margin: 0 0 1rem;
}

h2 .secno,
h3 .secno {
  margin-right: 0.6em;
}

h3 {
  font-size: 1.05rem;
  font-weight: 600;
  margin: 1.6rem 0 0.5rem;
}

p {
  margin: 0.9rem 0;
}

/* ---- genealogy table ---- */

.genealogy {
  width: 100%;
  border-collapse: collapse;
  font-size: 0.92rem;
  margin: 1.4rem 0;
  line-height: 1.6;
}

.genealogy caption {
  caption-side: bottom;
  font-size: 0.88rem;
  color: var(--ink-soft);
  padding-top: 0.6rem;
  text-align: center;
}

.genealogy caption .fig-label {
  font-weight: 600;
}

.genealogy th,
.genealogy td {
  padding: 0.45rem 0.6rem;
  text-align: left;
  vertical-align: top;
}

.genealogy thead th {
  border-top: 2px solid var(--rule-dark);
  border-bottom: 1px solid var(--rule-dark);
  font-weight: 600;
}

.genealogy tbody tr:last-child td {
  border-bottom: 2px solid var(--rule-dark);
}

.genealogy .now td {
  font-weight: 600;
}

.genealogy .nw {
  white-space: nowrap;
}

.table-wrap {
  overflow-x: auto;
  margin: 1.4rem 0;
}

.table-wrap .genealogy {
  margin: 0;
}

.classify {
  min-width: 34rem;
}

/* ---- theorem / definition boxes ---- */
/* Principle and Conjecture boxes (holographic page) share this rule on
   purpose: only the label tells them apart. */

.thmbox {
  border: 1px solid var(--rule-dark);
  padding: 1rem 1.3rem;
  margin: 1.6rem 0;
  line-height: 1.85;
}

.thmbox p {
  margin: 0.55rem 0;
}

.thmbox p:first-child {
  margin-top: 0;
}

.thmbox p:last-child {
  margin-bottom: 0;
}

.thm-head {
  font-weight: 700;
}

.thmbox .qed {
  float: right;
}

.thmbox + .thmbox {
  margin-top: 1rem;
}

.warnbox {
  border: 1px solid var(--rule-dark);
  border-left-width: 4px;
  padding: 1rem 1.3rem;
  margin: 1.6rem 0;
}

.thmbox .codeblock {
  margin: 0.7rem 0 0.2rem;
}

/* ---- displayed equations (holographic page) ---- */

.eq {
  display: flex;
  align-items: center;
  justify-content: center;
  position: relative;
  margin: 1.4rem 0;
  padding: 0 3.2rem;
  font-size: 1.12rem;
}

.eq-body {
  font-family: "STIX Two Text", "Times New Roman", serif;
  white-space: nowrap;
}

.eq-no {
  position: absolute;
  right: 0;
  font-size: 1rem;
}

.frac {
  display: inline-flex;
  flex-direction: column;
  align-items: center;
  vertical-align: middle;
  margin: 0 0.15em;
  line-height: 1.25;
}

.frac > span:first-child {
  border-bottom: 1px solid var(--ink);
  padding: 0 0.3em;
  align-self: stretch;
  text-align: center;
}

.ss {
  display: inline-flex;
  flex-direction: column;
  vertical-align: 0.45em;
  font-size: 0.66em;
  line-height: 1;
  margin-left: 0.05em;
}

.abstract .pacs {
  display: block;
  margin-top: 0.7rem;
  font-size: 0.85rem;
  color: var(--ink-faint);
  text-align: center;
  letter-spacing: 0.02em;
}

/* ---- pull quotes ---- */

.pullquote {
  margin: 2.2rem auto;
  max-width: 32rem;
  padding: 0;
  border-top: 1px solid var(--rule-dark);
  border-bottom: 1px solid var(--rule-dark);
  text-align: center;
}

.pullquote p {
  margin: 1.05rem 0.5rem;
  font-size: 1.12rem;
  font-weight: 600;
  line-height: 1.9;
}

.pullquote p:lang(en) {
  font-style: italic;
  font-weight: 500;
}

.warnbox .thm-head {
  font-variant: small-caps;
  letter-spacing: 0.08em;
}

/* ---- property list (§4) ---- */

.props {
  margin: 1.2rem 0;
  padding: 0;
}

.props dt {
  font-weight: 600;
  margin-top: 1.2rem;
}

.props dd {
  margin: 0.2rem 0 0 0;
}

/* ---- FAQ ---- */

.faq {
  margin: 1.2rem 0;
  padding: 0;
}

.faq dt {
  font-weight: 600;
  margin-top: 1.4rem;
}

.faq dt::before {
  content: "Q. ";
}

.faq dd {
  margin: 0.3rem 0 0 0;
}

.faq dd::before {
  content: "A. ";
  font-weight: 600;
}

/* ---- footnotes ---- */

.footnotes {
  margin-top: 3rem;
  border-top: 1px solid var(--rule);
  padding-top: 0.8rem;
  font-size: 0.85rem;
  color: var(--ink-faint);
  line-height: 1.7;
}

.footnotes p {
  margin: 0.4rem 0;
}

/* ---- footer ---- */

.site-footer {
  max-width: 44rem;
  margin: 0 auto;
  padding: 1.6rem 1.25rem 3rem;
  border-top: 2px solid var(--rule-dark);
  font-size: 0.9rem;
  color: var(--ink-soft);
}

.cite-head {
  font-variant: small-caps;
  letter-spacing: 0.1em;
  font-weight: 600;
  color: var(--ink);
  margin: 0 0 0.5rem;
}

.bibtex {
  border: 1px solid var(--rule);
  background: #f7f7f5;
  padding: 0.9rem 1.1rem;
  font-family: "Courier New", Courier, monospace;
  font-size: 0.78rem;
  line-height: 1.55;
  overflow-x: auto;
  margin: 0 0 1.4rem;
  color: var(--ink);
}

.share-row {
  display: flex;
  flex-wrap: wrap;
  gap: 1rem;
  align-items: center;
  margin: 1rem 0 1.6rem;
}

.share-button {
  display: inline-block;
  border: 1px solid var(--ink);
  padding: 0.35rem 0.95rem;
  text-decoration: none;
  font-size: 0.9rem;
  color: var(--ink);
}

.share-button:hover {
  background: #f0f0ee;
}

.site-footer .smallprint {
  font-size: 0.8rem;
  color: var(--ink-faint);
  margin-top: 1.6rem;
  line-height: 1.7;
}

.site-footer .smallprint p {
  margin: 0.3rem 0;
}

/* ---- companion link (main page -> guide) ---- */

.companion {
  display: inline-block;
  margin: 1.7rem auto 0;
  padding: 0.45rem 1.15rem;
  border: 1px solid var(--rule-dark);
  font-size: 0.92rem;
}

/* ---- guide page ---- */

code {
  font-family: "Courier New", Courier, monospace;
  font-size: 0.88em;
}

.tldr {
  border: 3px double var(--rule-dark);
  padding: 1rem 1.3rem;
  margin: 2.2rem auto 0;
  max-width: 36rem;
  font-size: 0.96rem;
  line-height: 1.8;
  text-align: justify;
}

.tldr .tldr-head {
  display: block;
  text-align: center;
  font-variant: small-caps;
  letter-spacing: 0.12em;
  font-weight: 700;
  margin-bottom: 0.4rem;
}

.steps {
  margin: 1.4rem 0;
  padding-left: 1.5rem;
}

.steps li {
  margin: 1rem 0;
}

.steps li::marker {
  font-weight: 700;
}

.steps .step-name {
  font-weight: 600;
}

.code-sample {
  margin: 1.8rem 0;
  text-align: left;
}

.code-sample .code-title {
  display: flex;
  justify-content: space-between;
  align-items: center;
  gap: 0.8rem;
  max-width: none;
  margin: 0;
  border: 1px solid var(--rule);
  border-bottom: none;
  background: #efefec;
  padding: 0.35rem 1.1rem;
  font-size: 0.84rem;
  color: var(--ink-soft);
  text-align: left;
}

.codeblock {
  border: 1px solid var(--rule);
  background: #f7f7f5;
  padding: 0.9rem 1.1rem;
  margin: 0;
  font-family: "Courier New", Courier, monospace;
  font-size: 0.78rem;
  line-height: 1.6;
  overflow-x: auto;
  color: var(--ink);
  text-align: left;
}

.codeblock code {
  font-size: inherit;
}

.copy-btn {
  flex-shrink: 0;
  border: 1px solid var(--ink);
  background: var(--paper);
  padding: 0.1rem 0.65rem;
  font-family: inherit;
  font-size: 0.8rem;
  color: var(--ink);
  cursor: pointer;
}

.copy-btn:hover {
  background: #f0f0ee;
}

.checklist {
  list-style: none;
  margin: 1.2rem 0;
  padding: 0;
}

.checklist li {
  position: relative;
  margin: 0.55rem 0;
  padding-left: 1.7em;
}

.checklist li::before {
  content: "☐";
  position: absolute;
  left: 0.2em;
}

/* ---- back link (klein page) ---- */

.backlink {
  margin-top: 2.6rem;
  font-size: 0.95rem;
}

/* ---- responsive ---- */

@media (max-width: 480px) {
  body {
    font-size: 1rem;
  }

  .site-header {
    flex-direction: column;
    gap: 0.15rem;
  }

  .genealogy {
    font-size: 0.84rem;
  }

  .genealogy th,
  .genealogy td {
    padding: 0.4rem 0.35rem;
  }
}

@media (prefers-reduced-motion: reduce) {
  * {
    animation: none !important;
    transition: none !important;
  }
}