/* Base
   ------------------------------------------------------------------ */

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

html { -webkit-text-size-adjust: 100%; }

body {
  margin: 0;
  background: var(--surface);
  color: var(--fg);
  font-family: var(--font-body);
  font-size: var(--fs-body);
  line-height: var(--lh-body);
  font-variant-numeric: tabular-nums;
  -webkit-font-smoothing: antialiased;
}

:focus-visible {
  outline: 2px solid var(--fg);
  outline-offset: 3px;
}

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

.wrap {
  max-width: var(--wrap);
  margin-inline: auto;
  padding-inline: var(--s-5);
}

.cos-container {
  max-width: 1280px;
  margin-inline: auto;
  padding-inline: clamp(24px, 6vw, 96px);
}

/* Typography
   ------------------------------------------------------------------ */

.display, .head, .subhead, .small, .annotation {
  font-family: var(--font-display);
  margin: 0;
}

.display {
  font-size: var(--fs-display);
  line-height: var(--lh-display);
  letter-spacing: var(--tr-display);
  font-weight: 600;
  max-width: 18ch;
}

.head {
  font-size: var(--fs-head);
  line-height: var(--lh-head);
  letter-spacing: var(--tr-head);
  font-weight: 500;
  max-width: 26ch;
}

.subhead {
  font-size: var(--fs-subhead);
  line-height: var(--lh-subhead);
  letter-spacing: var(--tr-subhead);
  font-weight: 500;
}

.small { font-size: var(--fs-small); line-height: 1.5; font-weight: 400; }

.annotation {
  font-size: var(--fs-annotation);
  line-height: var(--lh-annotation);
  letter-spacing: var(--tr-annotation);
  font-weight: 400;
  color: var(--fg-muted);
}

.prose { max-width: var(--measure); }
.prose p { margin: 0 0 var(--s-4); }
.prose p:last-child { margin-bottom: 0; }
.lead { font-size: 18px; line-height: 1.55; }

a {
  color: var(--fg);
  text-decoration: underline;
  text-decoration-thickness: 0.5px;
  text-underline-offset: 3px;
}
a:hover { text-decoration-thickness: 1.5px; }

/* Rule
   ------------------------------------------------------------------ */

.rule { display: block; width: 100%; border: 0; border-top: var(--w-object) solid var(--rule-object); margin: var(--s-6) 0; }
.rule--cut { border-top: var(--w-cut) solid var(--rule-cut); }
.rule--dimension { border-top: var(--w-dimension) solid var(--rule-dimension); }

/* Sheet
   ------------------------------------------------------------------ */

.sheet { background: var(--surface); padding: var(--sheet-pad); }
.sheet--bond { background: var(--c-bond); }
.sheet--framed { border: var(--w-cut) solid var(--rule-cut); }

/* Zone
   ------------------------------------------------------------------ */

.zone { padding-block: var(--zone-pad); }
.zone--tight { padding-block: var(--s-7); }
.zone__marker { display: block; margin-bottom: var(--s-4); }

/* Split — asymmetric by default
   ------------------------------------------------------------------ */

.split { display: grid; grid-template-columns: 8fr 4fr; gap: var(--s-7); align-items: start; }
.split--7-5 { grid-template-columns: 7fr 5fr; }
.split--5-7 { grid-template-columns: 5fr 7fr; }
.split--reverse > :first-child { order: 2; }

@media (max-width: 760px) {
  .split { grid-template-columns: 1fr; gap: var(--s-6); }
  .split--reverse > :first-child { order: 0; }
}

/* Grid — one per page maximum
   ------------------------------------------------------------------ */

.grid-3 { display: grid; grid-template-columns: repeat(3, minmax(0, 1fr)); gap: 0; }
.grid-3 > * { padding: var(--s-5) var(--s-5) var(--s-5) 0; border-top: var(--w-object) solid var(--rule-object); }

@media (max-width: 760px) {
  .grid-3 { grid-template-columns: 1fr; }
}

/* Register — inline technical identifier
   ------------------------------------------------------------------ */

.register {
  font-family: var(--font-display);
  font-size: var(--fs-annotation);
  letter-spacing: var(--tr-annotation);
  color: var(--fg-muted);
  font-variant-numeric: tabular-nums;
}

/* Title block
   ------------------------------------------------------------------ */

.title-block {
  border-top: var(--w-cut) solid var(--rule-cut);
  padding-top: var(--s-3);
  display: grid;
  grid-template-columns: repeat(4, minmax(0, 1fr));
  gap: var(--s-3);
}

.title-block__label {
  display: block;
  font-family: var(--font-display);
  font-size: var(--fs-annotation);
  letter-spacing: var(--tr-annotation);
  color: var(--fg-muted);
  margin-bottom: var(--s-1);
}

.title-block__value {
  display: block;
  font-family: var(--font-display);
  font-size: 13px;
  font-variant-numeric: tabular-nums;
}

.title-block--inline {
  display: block;
  font-family: var(--font-display);
  font-size: var(--fs-annotation);
  letter-spacing: var(--tr-annotation);
  color: var(--fg-muted);
  font-variant-numeric: tabular-nums;
  border-top: var(--w-dimension) solid var(--rule-dimension);
  padding-top: var(--s-2);
}

@media (max-width: 560px) {
  .title-block { grid-template-columns: repeat(2, minmax(0, 1fr)); gap: var(--s-4) var(--s-3); }
}

/* Dimension
   ------------------------------------------------------------------ */

.dim { margin: var(--s-5) 0; }
.dim__label { margin-bottom: var(--s-5); }

.dim__track {
  position: relative;
  width: var(--span, 100%);
  height: 0;
  border-top: var(--w-object) solid var(--fg-muted);
  margin-bottom: var(--s-6);
}

.dim__track::before,
.dim__track::after {
  content: "";
  position: absolute;
  top: -6px;
  width: 0;
  height: 12px;
  border-left: var(--w-object) solid var(--fg-muted);
  transform: rotate(45deg);
}
.dim__track::before { left: 0; }
.dim__track::after { right: 0; }

.dim__ext {
  position: absolute;
  top: -18px;
  width: 0;
  height: 30px;
  border-left: var(--w-dimension) solid var(--rule-dimension);
}
.dim__ext--start { left: 0; }
.dim__ext--end { right: 0; }

.dim__value {
  position: absolute;
  bottom: 7px;
  left: 50%;
  transform: translateX(-50%);
  white-space: nowrap;
  font-family: var(--font-display);
  font-size: 13px;
  font-variant-numeric: tabular-nums;
}

.dim__value--outside {
  left: auto;
  right: -12px;
  transform: translateX(100%);
  bottom: -7px;
}

.dim__track--changed { border-top-color: var(--change); }
.dim__track--changed::before,
.dim__track--changed::after { border-left-color: var(--change); }
.dim__track--changed .dim__value { color: var(--change); }

.dim__break {
  position: absolute;
  top: -7px;
  left: 50%;
  width: 12px;
  height: 15px;
  transform: translateX(-50%);
}
.dim__break::before,
.dim__break::after {
  content: "";
  position: absolute;
  top: 0;
  width: 0;
  height: 15px;
  border-left: var(--w-object) solid currentColor;
  transform: rotate(28deg);
}
.dim__break::before { left: 2px; }
.dim__break::after { left: 8px; }

/* Table
   ------------------------------------------------------------------ */

.table { width: 100%; border-collapse: collapse; font-variant-numeric: tabular-nums; }
.table th {
  text-align: left;
  font-family: var(--font-display);
  font-size: var(--fs-annotation);
  letter-spacing: var(--tr-annotation);
  font-weight: 400;
  color: var(--fg-muted);
  padding: 0 var(--s-4) var(--s-2) 0;
  border-bottom: var(--w-object) solid var(--rule-object);
}
.table td {
  font-family: var(--font-display);
  font-size: var(--fs-small);
  padding: var(--s-3) var(--s-4) var(--s-3) 0;
  border-bottom: var(--w-dimension) solid var(--rule-dimension);
  vertical-align: top;
}
.table td:last-child, .table th:last-child { padding-right: 0; }

/* Buttons
   ------------------------------------------------------------------ */

.btn {
  display: inline-block;
  font-family: var(--font-display);
  font-size: var(--fs-small);
  font-weight: 500;
  line-height: 1;
  padding: 13px 20px;
  border-radius: var(--radius);
  border: var(--w-cut) solid var(--btn-border);
  background: var(--btn-bg);
  color: var(--btn-fg);
  text-decoration: none;
  cursor: pointer;
}
.btn:hover {
  background: transparent;
  color: var(--btn-border);
}

.btn--ghost {
  background: transparent;
  color: var(--btn-border);
}
.btn--ghost:hover {
  background: var(--btn-bg);
  color: var(--btn-fg);
}

/* Sheet grid — the page layout model
   ------------------------------------------------------------------
   Twelve columns. The first two are the annotation gutter: register
   codes, dates, zone markers and field labels live there, the way
   they run down the left edge of a drawing sheet. Content occupies
   the remaining ten. This is what stops every section from stranding
   itself in the left third of a wide page.                          */

.grid {
  display: grid;
  grid-template-columns: repeat(12, minmax(0, 1fr));
  column-gap: var(--gutter);
  row-gap: var(--s-5);
  align-items: start;
}

.g-gutter { grid-column: 1 / 3; }
.g-main   { grid-column: 3 / 10; }
.g-wide   { grid-column: 3 / 13; }
.g-side   { grid-column: 10 / 13; }
.g-half-l { grid-column: 3 / 8; }
.g-half-r { grid-column: 8 / 13; }
.g-full   { grid-column: 1 / 13; }

@media (max-width: 900px) {
  .g-gutter, .g-main, .g-wide, .g-side,
  .g-half-l, .g-half-r, .g-full { grid-column: 1 / 13; }
  .g-gutter { margin-bottom: calc(var(--s-3) * -1); }
}

/* Spec list — term and description in aligned columns.
   Replaces the stacked prose block, which left the page half empty. */

.spec-list { border-top: var(--w-object) solid var(--object); }

.spec-row {
  display: grid;
  grid-template-columns: repeat(12, minmax(0, 1fr));
  column-gap: var(--gutter);
  padding: var(--s-4) 0;
  border-bottom: var(--w-dimension) solid var(--dimension);
}

.spec-row__index { grid-column: 1 / 3; }
.spec-row__term  { grid-column: 3 / 8; }
.spec-row__desc  { grid-column: 8 / 13; color: var(--annotation); }

@media (max-width: 900px) {
  .spec-row { row-gap: var(--s-2); }
  .spec-row__index, .spec-row__term, .spec-row__desc { grid-column: 1 / 13; }
}

/* Rules align to content columns, never to the container.
   A rule that runs past the content it divides underlines nothing.  */

.rule--main { margin-left: 0; }
.zone > .rule:first-child { margin-top: 0; }