/* UG · p4-spec · homepage styles. All values come from tokens.css. */

/* ---------- Base ------------------------------------------------------ */
*, *::before, *::after { box-sizing: border-box; }
html { -webkit-text-size-adjust: 100%; text-size-adjust: 100%; scroll-behavior: auto; }
body {
  position: relative;
  margin: 0;
  background: var(--paper);
  color: var(--ink);
  font-family: var(--font-sans);
  font-size: var(--fs-body);
  font-stretch: var(--wdth-text);
  font-weight: var(--w-text);
  line-height: var(--lh-body);
  letter-spacing: var(--tr-body);
  font-kerning: normal;
  font-variant-numeric: lining-nums proportional-nums;  /* never tnum: it slashes the zero */
  -webkit-font-smoothing: antialiased;
  -moz-osx-font-smoothing: grayscale;
  overflow-x: clip;
}
h1, h2, h3, p, dl, dd, ol, ul, figure { margin: 0; padding: 0; }
ol, ul { list-style: none; }
img, svg { display: block; max-width: 100%; height: auto; }
a { color: inherit; text-decoration: none; }
a:focus-visible, .btn:focus-visible, summary:focus-visible { outline: 1px solid var(--ink); outline-offset: 3px; }
::selection { background: var(--brand); color: var(--brand-ink); }

/* ---------- Sheet, rails, registration marks ------------------------- */
.sheet {
  width: min(100% - 2 * var(--margin), var(--sheet-max));
  margin-inline: auto;
  padding-inline: var(--inset);
}
.sheet--bleed { padding-inline: 0; }

/* The two vertical rails run the full height of the page. */
.rails {
  position: absolute;          /* spans the whole document, not a fixed layer */
  inset: 0;
  margin-inline: auto;
  width: min(100% - 2 * var(--margin), var(--sheet-max));
  border-inline: var(--hairline) solid var(--rule);
  pointer-events: none;
  z-index: 20;                 /* over content, under the nav strip */
}

/* Every section starts on a full-bleed hairline; where it crosses a rail,
   a darker registration "+" marks the intersection. */
main > section, .foot {
  position: relative;
  border-top: var(--hairline) solid var(--rule);
  --rail-x: calc((100% - min(100% - 2 * var(--margin), var(--sheet-max))) / 2);
}
main > section::before, main > section::after, .foot::before, .foot::after,
.nav::before, .nav::after {
  content: "";
  position: absolute;
  top: calc(var(--mark) / -2 - 0.5px);
  width: var(--mark);
  height: var(--mark);
  --mark-c: var(--rule-strong);
  background:
    linear-gradient(var(--mark-c), var(--mark-c)) center / 1px 100% no-repeat,
    linear-gradient(var(--mark-c), var(--mark-c)) center / 100% 1px no-repeat;
  pointer-events: none;
  z-index: 29;          /* under the sticky nav, over content */
}
main > section::before, .foot::before, .nav::before { left: calc(var(--rail-x) - var(--mark) / 2 + 0.5px); }
main > section::after, .foot::after, .nav::after { right: calc(var(--rail-x) - var(--mark) / 2 + 0.5px); }
/* The nav carries its own marks on its bottom hairline; the hero has none. */
.nav { --rail-x: calc((100% - min(100% - 2 * var(--margin), var(--sheet-max))) / 2); }
.nav::before, .nav::after { top: auto; bottom: calc(var(--mark) / -2 - 0.5px); z-index: 31; }
main > section.hero::before, main > section.hero::after { display: none; }
/* The volt band is light, so registration marks keep their normal colour across it. */

.grid {
  display: grid;
  grid-template-columns: repeat(var(--cols), minmax(0, 1fr));
  column-gap: var(--gutter);
}

/* ---------- Type roles ---------------------------------------------- */
.display {
  font-size: var(--fs-display);
  font-stretch: var(--wdth-display);
  font-weight: var(--w-display);
  line-height: var(--lh-display);
  letter-spacing: var(--tr-display);
  text-wrap: balance;
}
.statement {
  font-size: var(--fs-statement);
  font-stretch: var(--wdth-display);
  font-weight: var(--w-display);
  line-height: var(--lh-statement);
  letter-spacing: var(--tr-statement);
  text-wrap: pretty;
}
.cont { color: var(--ink-3); }
.lead {
  font-size: var(--fs-lead);
  line-height: var(--lh-lead);
  letter-spacing: var(--tr-lead);
  color: var(--ink-2);
  max-width: 34ch;
  text-wrap: pretty;
}
/* The one quiet label: 14px, sentence case, grey, no tracking. Section
   indexes, spec keys, column heads, captions and title-block keys. */
.index, .spec dt, .ledger th, .tb__k, .tb__rev, .plate figcaption, .slot__s, .cta__note {
  font-size: var(--fs-label);
  line-height: var(--lh-label);
  letter-spacing: var(--tr-label);
  font-weight: var(--w-text);
  color: var(--ink-2);
}
.index .n { display: inline-block; min-width: 2.25em; }
/* Figures: kerning off and a hair of tracking, so "28.10.26" and "7.4"
   never close up. Never tnum: Mona Sans slashes its tabular zero. */
.num { font-kerning: none; letter-spacing: 0.02em; }

/* ---------- Actions -------------------------------------------------- */
.btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  height: 40px;
  padding: 0 var(--s-4);
  background: var(--brand);
  color: var(--brand-ink);
  border: var(--hairline) solid var(--brand);
  border-radius: var(--radius);
  font-size: var(--fs-label);
  font-weight: var(--w-strong);
  letter-spacing: 0;
  white-space: nowrap;
  transition: background-color var(--dur) var(--ease), color var(--dur) var(--ease);
}
.btn:hover { background: var(--ink); color: var(--paper); border-color: var(--ink); }
.btn--lg { height: 52px; padding: 0 var(--s-5); font-size: var(--fs-body); }

.link {
  text-decoration: underline;
  text-decoration-thickness: 1px;
  text-underline-offset: 0.28em;
  text-decoration-color: var(--rule-strong);
  transition: text-decoration-color var(--dur) var(--ease);
}
.link:hover { text-decoration-color: var(--ink); }

.sig {
  display: inline-block;
  width: 7px;
  height: 7px;
  margin-right: var(--s-2);
  background: var(--signal);
  transform: translateY(-1px);
}

/* ---------- Spec lists (keys right-aligned to a shared axis) ---------- */
.spec { display: grid; }
.spec > div {
  display: grid;
  grid-template-columns: 6.5em minmax(0, 1fr);
  column-gap: var(--s-4);
  align-items: baseline;
  padding-block: 3px;
}
.spec dt { text-align: right; }
.spec dd { font-size: var(--fs-label); line-height: var(--lh-label); letter-spacing: var(--tr-label); color: var(--ink); }

/* ---------- Nav ------------------------------------------------------ */
.nav {
  position: sticky;
  top: 0;
  z-index: 30;
  background: var(--paper);
  border-bottom: var(--hairline) solid var(--rule);
}
.nav__in {
  position: relative;
  height: var(--nav-h);
  display: grid;
  grid-template-columns: repeat(var(--cols), minmax(0, 1fr));
  column-gap: var(--gutter);
  align-items: center;
}
.wordmark {
  grid-column: 1 / span 3;
  font-size: var(--fs-body);
  font-stretch: var(--wdth-display);
  font-weight: var(--w-strong);
  letter-spacing: -0.012em;
  line-height: 1;
}
.nav__links { grid-column: 4 / span 6; display: flex; gap: var(--s-6); }
.nav__links a {
  font-size: var(--fs-label);
  color: var(--ink-2);
  transition: color var(--dur) var(--ease);
  padding-block: var(--s-3);
}
.nav__links a:hover { color: var(--ink); }
.nav__cta { grid-column: 10 / -1; justify-self: end; }
.menu { display: none; }

/* ---------- Hero ----------------------------------------------------- */
main > section.hero { border-top: 0; }
.hero__in {
  min-height: calc(100svh - var(--nav-h));
  display: flex;
  flex-direction: column;
  padding-block: var(--s-5) var(--s-8);
}
.hero__head { display: flex; justify-content: space-between; }
.hero .display { margin-top: var(--s-10); }
.hero__foot {
  margin-top: auto;
  padding-top: var(--s-9);
  display: grid;
  grid-template-columns: repeat(var(--cols), minmax(0, 1fr));
  column-gap: var(--gutter);
  align-items: end;
}
.hero__lede { grid-column: 1 / span 5; }
.hero__lede .btn { margin-top: var(--s-6); }
.spec--cover { grid-column: 8 / -1; justify-self: end; min-width: 20em; }

/* ---------- Section rhythm ------------------------------------------- */
main > section:not(.hero):not(.principle) { padding-block: var(--section); }
.index + * { min-width: 0; }
main > section > .sheet > .index { grid-column: 1 / span 3; }

/* ---------- Principle: the one graphite band ------------------------- */
.principle { background: var(--band); color: var(--band-ink); border-top-color: var(--band); }
.principle > .sheet {
  padding-block: var(--s-11);
  box-shadow: inset 1px 0 var(--band-rule), inset -1px 0 var(--band-rule);  /* rails, on graphite */
}
.principle .index, .principle .cont { color: var(--band-ink-2); }
.principle__text { grid-column: 4 / span 8; max-width: 25ch; }

/* ---------- How it works: one procedure, three footnotes ------------- */
.how__main { grid-column: 4 / -1; }
.procedure {
  font-size: var(--fs-statement);
  font-stretch: var(--wdth-display);
  font-weight: var(--w-display);
  line-height: var(--lh-statement);
  letter-spacing: var(--tr-statement);
}
.procedure > span { display: block; }
.ref {
  font-size: var(--fs-label);
  font-stretch: var(--wdth-text);
  font-weight: var(--w-text);
  letter-spacing: 0;
  line-height: 0;
  color: var(--ink-2);
  vertical-align: baseline;
  position: relative;
  top: calc(var(--fs-statement) * -0.44);
  margin-left: 0.15em;
}
.notes { margin-top: var(--s-8); max-width: 34rem; }
.notes::before {               /* the footnote rule */
  content: "";
  display: block;
  width: var(--s-9);
  border-top: var(--hairline) solid var(--rule-strong);
  margin-bottom: var(--s-4);
}
.notes li {
  display: grid;
  grid-template-columns: var(--s-6) minmax(0, 1fr);
  align-items: baseline;
  padding-block: var(--s-1);
  color: var(--ink-2);
  text-wrap: pretty;
}
.notes__n { font-size: var(--fs-label); color: var(--ink); }

/* ---------- Work ----------------------------------------------------- */
.work__head { padding-bottom: var(--s-9); align-items: end; }
.work__head > .index { align-self: start; }
.work__title { grid-column: 4 / span 5; }
.work__name {
  font-size: var(--fs-title);
  font-stretch: var(--wdth-display);
  font-weight: var(--w-display);
  line-height: var(--lh-title);
  letter-spacing: var(--tr-title);
}
.work__name .cont { display: block; }
.work__line { margin-top: var(--s-5); }
.work__spec { grid-column: 9 / -1; }

/* One plate at 1.4x, two details, standing on a shared baseline. */
.plates {
  display: grid;
  grid-template-columns: 2fr 1fr 1fr;
  border-block: var(--hairline) solid var(--rule);
}
.plate {
  display: flex;
  flex-direction: column;
  justify-content: flex-end;
  align-items: center;
  padding: var(--s-8) var(--s-5) var(--s-6);
}
.plate + .plate { border-left: var(--hairline) solid var(--rule); }
.plate--lg { --plate-w: 336px; }
.plate--sm { --plate-w: 240px; }
.plate > * { width: min(100%, var(--plate-w)); }
.plate img { background: var(--ink); }
.plate figcaption { margin-top: var(--s-4); }
.plate .fig { display: block; color: var(--ink); }

/* Apps without screens are rows of text, not boxes. */
.slots { grid-column: 4 / -1; margin-top: var(--s-8); border-bottom: var(--hairline) solid var(--rule); }
.slot {
  display: grid;
  grid-template-columns: minmax(0, 1fr) auto;
  column-gap: var(--s-5);
  align-items: baseline;
  padding-block: var(--s-5);
  border-top: var(--hairline) solid var(--rule);
}
.slot__t {
  font-size: var(--fs-lead);
  font-weight: var(--w-text);
  line-height: var(--lh-lead);
  letter-spacing: var(--tr-lead);
}
.slot__s .link { color: var(--ink); }

/* ---------- Log (ledger) --------------------------------------------- */
.ledger {
  grid-column: 4 / -1;
  width: 100%;
  border-collapse: collapse;
}
.ledger th {
  text-align: left;
  padding: 0 var(--s-5) var(--s-3) 0;
  border-bottom: var(--hairline) solid var(--rule);
}
.ledger td {
  padding: var(--s-5) var(--s-5) var(--s-5) 0;
  border-bottom: var(--hairline) solid var(--rule);
  vertical-align: baseline;
}
.ledger .r { text-align: right; padding-right: 0; }
.ledger .d, .ledger .p { font-size: var(--fs-label); color: var(--ink-2); white-space: nowrap; }
.ledger .d { width: 9em; }
.ledger .e {
  font-size: var(--fs-lead);
  line-height: var(--lh-lead);
  letter-spacing: var(--tr-lead);
  font-variant-numeric: normal;
  text-wrap: pretty;
}

/* ---------- About ---------------------------------------------------- */
.about__text { grid-column: 4 / span 8; max-width: 24ch; }

/* ---------- CTA ------------------------------------------------------ */
.cta__main { grid-column: 4 / -1; }
.cta__t {
  font-size: var(--fs-title);
  font-stretch: var(--wdth-display);
  font-weight: var(--w-display);
  line-height: var(--lh-title);
  letter-spacing: var(--tr-title);
  max-width: 14ch;
  text-wrap: balance;
}
.cta__t .cont { display: block; }
.cta__row { display: flex; align-items: center; gap: var(--s-6); margin-top: var(--s-8); flex-wrap: wrap; }

/* ---------- Footer: title block -------------------------------------- */
.foot { padding-bottom: var(--s-8); }
.foot .sheet { padding-inline: 0; }
.tblock {
  display: grid;
  grid-template-columns: repeat(12, minmax(0, 1fr));
  border-bottom: var(--hairline) solid var(--rule);
}
.tb {
  display: flex;
  flex-direction: column;
  gap: var(--s-2);
  padding: var(--s-4) var(--s-5) var(--s-5);
  min-height: 96px;
  font-size: var(--fs-label);
  line-height: var(--lh-label);
}
.tb--mark { grid-column: 1 / span 6; grid-row: 1 / span 2; justify-content: space-between; padding-left: var(--inset); }
.tb:nth-child(2) { grid-column: 7 / span 3; }
.tb:nth-child(3) { grid-column: 10 / span 3; }
.tb:nth-child(4) { grid-column: 7 / span 3; }
.tb:nth-child(5) { grid-column: 10 / span 3; }
.tb:not(.tb--mark) { border-left: var(--hairline) solid var(--rule); }
.tb:nth-child(4), .tb:nth-child(5) { border-top: var(--hairline) solid var(--rule); }
.tb a { transition: color var(--dur) var(--ease); }
.tb a:hover { color: var(--ink-2); }
.tb__links { display: flex; flex-wrap: wrap; column-gap: var(--s-5); row-gap: var(--s-1); }
.wordmark--lg {
  font-size: var(--fs-statement);
  font-stretch: var(--wdth-display);
  font-weight: var(--w-display);
  letter-spacing: var(--tr-statement);
  line-height: 1;
}

/* =====================================================================
   Phone (≤760px): four columns, everything re-set, not squeezed
   ===================================================================== */
@media (max-width: 760px) {
  .btn { height: 44px; }
  .btn--lg { height: 52px; }

  /* One row: wordmark and Menu. The menu drops a ruled index below. */
  .nav { position: relative; }
  .nav__in { grid-template-columns: minmax(0, 1fr) auto; }
  .nav__links, .nav__cta { display: none; }
  .wordmark { grid-column: 1; font-size: 15px; min-height: 44px; display: flex; align-items: center; }
  .menu { display: block; grid-column: 2; }
  .menu summary {
    list-style: none;
    min-height: 44px;
    min-width: 44px;
    display: flex;
    align-items: center;
    justify-content: flex-end;
    font-size: var(--fs-label);
    cursor: pointer;
    -webkit-tap-highlight-color: transparent;
  }
  .menu summary::-webkit-details-marker { display: none; }
  .menu__close, .menu[open] .menu__open { display: none; }
  .menu[open] .menu__close { display: inline; }
  .menu__panel {
    position: absolute;
    top: 100%;
    left: 0;
    right: 0;
    z-index: 32;
    background: var(--paper);
    border: var(--hairline) solid var(--rule);
    border-top: 0;
    margin-top: var(--hairline);
    padding-inline: var(--inset);
    display: flex;
    flex-direction: column;
  }
  .menu__panel a {
    min-height: 56px;
    display: flex;
    align-items: center;
    font-size: var(--fs-lead);
    letter-spacing: var(--tr-lead);
  }
  .menu__panel a + a { border-top: var(--hairline) solid var(--rule); }

  .hero__in { min-height: 0; padding-block: var(--s-4) var(--s-7); }
  .hero .display { margin-top: var(--s-9); }
  .hero__foot { padding-top: var(--s-8); row-gap: var(--s-8); }
  .hero__lede, .spec--cover { grid-column: 1 / -1; justify-self: stretch; min-width: 0; }
  .hero__lede .btn { width: 100%; }

  .spec > div { grid-template-columns: 6em minmax(0, 1fr); }
  .spec dt { text-align: left; }
  .spec--cover { border-top: var(--hairline) solid var(--rule); padding-top: var(--s-3); }

  main > section > .sheet > .index { grid-column: 1 / -1; margin-bottom: var(--s-6); }
  .principle > .sheet { padding-block: var(--s-9); }
  .principle__text, .about__text, .how__main { grid-column: 1 / -1; }

  .ref { margin-left: 0.1em; }
  .notes { margin-top: var(--s-7); }
  .notes li { grid-template-columns: var(--s-5) minmax(0, 1fr); padding-block: var(--s-2); }

  .work__head { padding-bottom: var(--s-8); row-gap: 0; }
  .work__spec { margin-top: var(--s-7); }
  .work__title, .work__spec { grid-column: 1 / -1; }
  .work__spec { border-top: var(--hairline) solid var(--rule); padding-top: var(--s-3); }

  .plates { grid-template-columns: repeat(2, minmax(0, 1fr)); }
  .plate--lg { grid-column: 1 / -1; --plate-w: 248px; }
  .plate--sm { --plate-w: 152px; }
  .plate { padding: var(--s-7) var(--s-4) var(--s-5); }
  .plate + .plate { border-left: 0; }
  .plate--sm { border-top: var(--hairline) solid var(--rule); justify-content: flex-start; }
  .plate--sm + .plate--sm { border-left: var(--hairline) solid var(--rule); }

  .slots { grid-column: 1 / -1; margin-top: var(--s-7); }
  .slot { padding-block: var(--s-4); }
  .slot__s .link { display: inline-flex; align-items: center; min-height: 44px; margin-block: -12px; }

  .ledger { grid-column: 1 / -1; }
  .ledger thead { display: none; }
  .ledger tr { display: grid; grid-template-columns: minmax(0, 1fr) auto; border-bottom: var(--hairline) solid var(--rule); padding: var(--s-4) 0; row-gap: var(--s-2); }
  .ledger tbody tr:first-child { border-top: var(--hairline) solid var(--rule); }
  .ledger td { border: 0; padding: 0; }
  .ledger .d { grid-column: 1; grid-row: 1; width: auto; }
  .ledger .p { grid-column: 2; grid-row: 1; }
  .ledger .e { grid-column: 1 / -1; grid-row: 2; }

  .cta__main { grid-column: 1 / -1; }
  .cta__row { gap: var(--s-4); margin-top: var(--s-7); }
  .cta__row .btn { width: 100%; }

  .tblock { grid-template-columns: 1fr 1fr; }
  .tblock > .tb { grid-column: auto; grid-row: auto; border-top: var(--hairline) solid var(--rule); border-left: 0; padding-left: var(--inset); }
  .tblock > .tb--mark { grid-column: 1 / -1; border-top: 0; gap: var(--s-5); }
  .tblock > .tb:nth-child(3), .tblock > .tb:nth-child(5) { border-left: var(--hairline) solid var(--rule); padding-left: var(--s-4); }
  .wordmark--lg { font-size: 34px; }
  .tb { min-height: 88px; gap: 0; }
  .tb a, .tb__links a { min-height: 44px; min-width: 44px; display: inline-flex; align-items: center; }
  .tb__links { row-gap: 0; }
  .tblock > .tb:not(.tb--mark) > :not(.tb__k) { min-height: 44px; display: flex; align-items: center; }
}