/* ============================================================
   Anthropc Spec Kit — drafting-table design system
   Off-white paper, ink-blue rules, stamp-red accents.
   ============================================================ */

:root {
  --paper:        #faf7ee;
  --paper-deep:   #f4f0e1;
  --paper-card:   #fffdf6;
  --grid-line:    #e3e8f4;
  --ink:          #1c2b47;
  --ink-soft:     #46587c;
  --ink-faint:    #6f7fa0;
  --rule:         #234a8a;
  --rule-soft:    #b9c6e2;
  --stamp-red:    #b3402e;
  --stamp-blue:   #1f4e8f;
  --margin-red:   #d99a8c;
  --field-bg:     #ffffff;
  --ok-green:     #2e7d4f;
  --warn-amber:   #9a6a1b;

  --serif: Georgia, "Iowan Old Style", "Times New Roman", serif;
  --sans: -apple-system, BlinkMacSystemFont, "Segoe UI", "Helvetica Neue", Arial, sans-serif;
  --mono: ui-monospace, "SF Mono", "Cascadia Mono", Menlo, Consolas, monospace;

  --measure: 68ch;
  --maxw: 1100px;
  --pad: clamp(1rem, 4vw, 2.5rem);
}

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

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

body {
  margin: 0;
  color: var(--ink);
  font-family: var(--sans);
  font-size: 1.0625rem;
  line-height: 1.65;
  background-color: var(--paper);
  background-image:
    linear-gradient(var(--grid-line) 1px, transparent 1px),
    linear-gradient(90deg, var(--grid-line) 1px, transparent 1px);
  background-size: 28px 28px;
  background-position: center top;
}

/* ---- Ruled margin: the red ledger line down the page ---- */
.sheet {
  position: relative;
  max-width: calc(var(--maxw) + 72px);
  margin: 0 auto;
  padding: 0 var(--pad);
}
.sheet::before {
  content: "";
  position: absolute;
  top: 0; bottom: 0;
  left: clamp(0.25rem, 2vw, 1.25rem);
  width: 2px;
  background: var(--margin-red);
  opacity: .7;
  pointer-events: none;
}

/* ---- Typography ---- */
h1, h2, h3, h4 {
  font-family: var(--serif);
  font-weight: 600;
  line-height: 1.25;
  color: var(--ink);
  margin: 0 0 .6em;
  text-wrap: balance;
}
h1 { font-size: clamp(2.1rem, 5.5vw, 3.4rem); letter-spacing: -0.01em; }
h2 { font-size: clamp(1.5rem, 3.4vw, 2.1rem); }
h3 { font-size: 1.25rem; }
p { margin: 0 0 1em; }
.lede {
  font-family: var(--serif);
  font-size: clamp(1.15rem, 2.4vw, 1.45rem);
  line-height: 1.6;
  color: var(--ink-soft);
  max-width: 60ch;
}
a { color: var(--rule); text-decoration-thickness: 1px; text-underline-offset: 3px; }
a:hover { color: var(--stamp-red); }
::selection { background: #dbe6fb; }

/* ---- Section numbering (§01) ---- */
.secnum {
  font-family: var(--mono);
  font-size: .85rem;
  font-weight: 700;
  letter-spacing: .14em;
  color: var(--stamp-blue);
  text-transform: uppercase;
  display: block;
  margin-bottom: .35rem;
}
.secnum::before { content: "§ "; }

.section {
  padding: clamp(2.5rem, 6vw, 4.5rem) 0;
  border-top: 2px solid var(--rule);
  position: relative;
}
.section:first-of-type { border-top: none; }

/* ---- Site header: document title block ---- */
.site-header {
  border-bottom: 3px double var(--rule);
  background: var(--paper-card);
}
.header-inner {
  max-width: calc(var(--maxw) + 72px);
  margin: 0 auto;
  padding: .9rem var(--pad);
  display: flex;
  align-items: center;
  gap: 1rem;
  flex-wrap: wrap;
}
.brand {
  display: flex;
  align-items: center;
  gap: .75rem;
  text-decoration: none;
  color: var(--ink);
  margin-right: auto;
}
.brand-mark {
  width: 44px; height: 44px;
  border: 2px solid var(--rule);
  display: grid;
  place-items: center;
  background: var(--paper);
  transform: rotate(-3deg);
}
.brand-mark svg { display: block; }
.brand-name {
  font-family: var(--mono);
  font-weight: 700;
  font-size: 1rem;
  letter-spacing: .08em;
  line-height: 1.25;
}
.brand-name small {
  display: block;
  font-weight: 400;
  font-size: .68rem;
  letter-spacing: .28em;
  color: var(--ink-faint);
}
.doc-meta {
  font-family: var(--mono);
  font-size: .72rem;
  color: var(--ink-faint);
  text-align: right;
  line-height: 1.7;
  border-left: 1px solid var(--rule-soft);
  padding-left: 1rem;
}
.doc-meta strong { color: var(--ink); }

/* ---- Nav ---- */
.nav { position: relative; }
.nav-list {
  list-style: none;
  margin: 0; padding: 0;
  display: flex;
  gap: .25rem;
  flex-wrap: wrap;
}
.nav-list a {
  display: block;
  padding: .55rem .8rem;
  font-family: var(--mono);
  font-size: .82rem;
  letter-spacing: .06em;
  text-transform: uppercase;
  text-decoration: none;
  color: var(--ink);
  border: 1px solid transparent;
  border-radius: 2px;
}
.nav-list a:hover { border-color: var(--rule-soft); color: var(--rule); }
.nav-list a[aria-current="page"] {
  background: var(--ink);
  color: var(--paper);
}
.nav-toggle {
  display: none;
  font-family: var(--mono);
  font-size: .85rem;
  letter-spacing: .1em;
  text-transform: uppercase;
  background: var(--paper);
  border: 2px solid var(--rule);
  color: var(--ink);
  padding: .55rem .9rem;
  cursor: pointer;
}
@media (max-width: 900px) {
  .nav-toggle { display: inline-block; }
  .nav-list { display: none; width: 100%; flex-direction: column; gap: 0; margin-top: .75rem; border-top: 1px solid var(--rule-soft); }
  .nav.open .nav-list { display: flex; }
  .nav-list a { border-bottom: 1px solid var(--rule-soft); border-radius: 0; }
}

/* ---- Stamps ---- */
.stamp {
  display: inline-block;
  font-family: var(--mono);
  font-weight: 700;
  font-size: .78rem;
  letter-spacing: .22em;
  text-transform: uppercase;
  color: var(--stamp-red);
  border: 2.5px solid var(--stamp-red);
  border-radius: 4px;
  padding: .45rem .9rem;
  transform: rotate(-4deg);
  background: rgba(179, 64, 46, .06);
  white-space: nowrap;
}
.stamp.blue {
  color: var(--stamp-blue);
  border-color: var(--stamp-blue);
  background: rgba(31, 78, 143, .06);
}
.stamp + .stamp { margin-left: .75rem; }

/* ---- Hero ---- */
.hero {
  padding: clamp(3rem, 8vw, 5.5rem) 0 clamp(2.5rem, 6vw, 4rem);
  position: relative;
}
.hero .sheet-inner { max-width: var(--measure); }
.hero-stamps { margin-bottom: 1.5rem; display: flex; flex-wrap: wrap; gap: .25rem; }
.hero-cta { display: flex; gap: 1rem; flex-wrap: wrap; margin-top: 2rem; }

/* ---- Buttons: drafting-ticket style ---- */
.btn {
  display: inline-block;
  font-family: var(--mono);
  font-size: .9rem;
  font-weight: 700;
  letter-spacing: .1em;
  text-transform: uppercase;
  text-decoration: none;
  padding: .9rem 1.6rem;
  border: 2px solid var(--ink);
  background: var(--ink);
  color: var(--paper);
  cursor: pointer;
  border-radius: 2px;
  box-shadow: 4px 4px 0 var(--rule-soft);
  transition: transform .12s ease, box-shadow .12s ease;
}
.btn:hover { color: var(--paper); transform: translate(-1px, -1px); box-shadow: 5px 5px 0 var(--rule-soft); }
.btn:active { transform: translate(2px, 2px); box-shadow: 2px 2px 0 var(--rule-soft); }
.btn.ghost {
  background: transparent;
  color: var(--ink);
}
.btn.ghost:hover { color: var(--ink); background: var(--paper-card); }
.btn.small { padding: .55rem 1rem; font-size: .78rem; }

/* ---- The Loop diagram ---- */
.loop-diagram {
  display: grid;
  grid-template-columns: repeat(4, 1fr);
  gap: 0;
  margin: 2.5rem 0 1rem;
  align-items: stretch;
}
.loop-step {
  background: var(--paper-card);
  border: 2px solid var(--rule);
  padding: 1.25rem 1rem;
  text-align: center;
  position: relative;
}
.loop-step:not(:last-child)::after {
  content: "→";
  position: absolute;
  right: -1.35rem;
  top: 50%;
  transform: translateY(-50%);
  font-size: 1.6rem;
  font-weight: 700;
  color: var(--stamp-red);
  z-index: 2;
}
.loop-step .loop-n {
  font-family: var(--mono);
  font-size: .75rem;
  letter-spacing: .2em;
  color: var(--stamp-red);
  font-weight: 700;
}
.loop-step h3 { margin: .4rem 0 .35rem; font-size: 1.15rem; }
.loop-step p { font-size: .9rem; margin: 0; color: var(--ink-soft); }
.loop-return {
  grid-column: 1 / -1;
  margin-top: 1.75rem;
  text-align: center;
  font-family: var(--mono);
  font-size: .85rem;
  color: var(--ink-soft);
  border: 1.5px dashed var(--rule);
  padding: .9rem 1rem;
  background: rgba(35, 74, 138, .05);
  letter-spacing: .04em;
}
@media (max-width: 760px) {
  .loop-diagram { grid-template-columns: 1fr; }
  .loop-step:not(:last-child)::after {
    content: "↓";
    right: 50%;
    top: auto;
    bottom: -1.5rem;
    transform: translateX(50%);
  }
  .loop-step { margin-bottom: 1.75rem; }
  .loop-step:last-of-type { margin-bottom: 0; }
}

/* ---- Cards ---- */
.card-grid {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(min(100%, 300px), 1fr));
  gap: 1.5rem;
  margin-top: 2rem;
}
.card {
  background: var(--paper-card);
  border: 2px solid var(--rule);
  padding: 1.5rem;
  box-shadow: 5px 5px 0 var(--rule-soft);
  display: flex;
  flex-direction: column;
}
.card h3 { margin-top: 0; }
.card .card-tag {
  font-family: var(--mono);
  font-size: .72rem;
  letter-spacing: .18em;
  text-transform: uppercase;
  color: var(--stamp-red);
  font-weight: 700;
  margin-bottom: .5rem;
}
.card p { flex: 1; font-size: .96rem; color: var(--ink-soft); }
.card .btn { align-self: flex-start; margin-top: .75rem; }

/* ---- Revision block (engineering table) ---- */
.revblock {
  width: 100%;
  border-collapse: collapse;
  margin: 2rem 0;
  font-family: var(--mono);
  font-size: .82rem;
}
.revblock caption {
  text-align: left;
  font-weight: 700;
  letter-spacing: .12em;
  text-transform: uppercase;
  font-size: .75rem;
  padding-bottom: .5rem;
  color: var(--ink);
}
.revblock th, .revblock td {
  border: 1.5px solid var(--rule);
  padding: .6rem .8rem;
  text-align: left;
  vertical-align: top;
}
.revblock thead th {
  background: var(--ink);
  color: var(--paper);
  letter-spacing: .1em;
  text-transform: uppercase;
  font-size: .72rem;
}
.revblock tbody tr:nth-child(even) { background: rgba(35,74,138,.045); }

/* ---- Comparison table ---- */
.compare {
  width: 100%;
  border-collapse: collapse;
  margin: 2rem 0;
  font-size: .95rem;
}
.compare caption {
  text-align: left;
  font-family: var(--mono);
  font-weight: 700;
  letter-spacing: .1em;
  text-transform: uppercase;
  font-size: .8rem;
  padding-bottom: .75rem;
}
.compare th, .compare td {
  border: 1.5px solid var(--rule-soft);
  padding: .75rem .9rem;
  text-align: left;
  vertical-align: top;
}
.compare thead th {
  font-family: var(--mono);
  font-size: .78rem;
  letter-spacing: .08em;
  text-transform: uppercase;
  background: var(--paper-deep);
  border-color: var(--rule);
}
.compare tbody th { font-family: var(--serif); font-weight: 600; }
.compare td.bad { color: var(--stamp-red); }
.compare td.good { color: var(--ok-green); font-weight: 600; }
.table-scroll { overflow-x: auto; }

/* ---- Callouts / annotations ---- */
.annotation {
  border-left: 4px solid var(--stamp-red);
  background: rgba(179, 64, 46, .06);
  padding: 1rem 1.25rem;
  margin: 1.25rem 0;
  font-size: .95rem;
}
.annotation .ann-label {
  font-family: var(--mono);
  font-size: .72rem;
  font-weight: 700;
  letter-spacing: .18em;
  text-transform: uppercase;
  color: var(--stamp-red);
  display: block;
  margin-bottom: .3rem;
}
.annotation p:last-child { margin-bottom: 0; }

.note-blue {
  border-left-color: var(--rule);
  background: rgba(35, 74, 138, .06);
}
.note-blue .ann-label { color: var(--rule); }

/* ---- Template source block ---- */
.template-source-wrap {
  margin: 2.5rem 0;
  border: 2px solid var(--rule);
  background: var(--field-bg);
}
.template-source-head {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 1rem;
  flex-wrap: wrap;
  padding: .8rem 1.1rem;
  border-bottom: 2px solid var(--rule);
  background: var(--paper-deep);
}
.template-source-head .file-name {
  font-family: var(--mono);
  font-size: .85rem;
  font-weight: 700;
  letter-spacing: .04em;
}
pre.template-source {
  margin: 0;
  padding: 1.5rem;
  overflow-x: auto;
  font-family: var(--mono);
  font-size: .86rem;
  line-height: 1.6;
  white-space: pre;
  color: var(--ink);
  max-height: 560px;
  overflow-y: auto;
}
.copy-feedback {
  font-family: var(--mono);
  font-size: .8rem;
  color: var(--ok-green);
  font-weight: 700;
  min-height: 1.2em;
}

/* ---- Two-column spec page: content + margin notes ---- */
.spec-layout {
  display: grid;
  grid-template-columns: minmax(0, 1fr);
  gap: 2rem;
  max-width: var(--maxw);
}
.spec-main { max-width: var(--measure); }
.spec-sec {
  border-top: 1px solid var(--rule-soft);
  padding: 1.75rem 0;
}
.spec-sec h3 {
  display: flex;
  align-items: baseline;
  gap: .75rem;
}
.spec-sec h3 .sec-no {
  font-family: var(--mono);
  font-size: .85rem;
  font-weight: 700;
  color: var(--stamp-red);
  letter-spacing: .1em;
  white-space: nowrap;
}

/* ---- Forms ---- */
.form {
  max-width: 560px;
  background: var(--paper-card);
  border: 2px solid var(--rule);
  padding: 2rem;
  box-shadow: 5px 5px 0 var(--rule-soft);
}
.field { margin-bottom: 1.25rem; }
.field label {
  display: block;
  font-family: var(--mono);
  font-size: .78rem;
  font-weight: 700;
  letter-spacing: .1em;
  text-transform: uppercase;
  margin-bottom: .4rem;
}
.field input[type="text"],
.field input[type="email"],
.field select,
.field textarea {
  width: 100%;
  font: inherit;
  padding: .7rem .85rem;
  border: 2px solid var(--rule);
  background: var(--field-bg);
  color: var(--ink);
  border-radius: 2px;
}
.field input:focus, .field select:focus, .field textarea:focus {
  outline: 3px solid rgba(35, 74, 138, .35);
  outline-offset: 1px;
}
.field .hint { font-size: .82rem; color: var(--ink-faint); margin-top: .3rem; }
.field-error {
  display: none;
  font-size: .85rem;
  color: var(--stamp-red);
  font-weight: 600;
  margin-top: .35rem;
}
.field.invalid input, .field.invalid select { border-color: var(--stamp-red); }
.field.invalid .field-error { display: block; }
.form-success {
  display: none;
  border: 2px dashed var(--ok-green);
  background: rgba(46, 125, 79, .07);
  padding: 1.5rem;
  margin-top: 1rem;
}
.form-success.show { display: block; }
.form-success h3 { color: var(--ok-green); margin-bottom: .3rem; }

/* ---- FAQ ---- */
.faq-list { max-width: var(--measure); }
.faq-list details {
  border: 2px solid var(--rule-soft);
  background: var(--paper-card);
  margin-bottom: 1rem;
  border-radius: 2px;
}
.faq-list summary {
  cursor: pointer;
  padding: 1rem 1.25rem;
  font-family: var(--serif);
  font-weight: 600;
  font-size: 1.1rem;
  list-style: none;
  display: flex;
  justify-content: space-between;
  align-items: center;
  gap: 1rem;
}
.faq-list summary::-webkit-details-marker { display: none; }
.faq-list summary::after {
  content: "+";
  font-family: var(--mono);
  font-size: 1.4rem;
  color: var(--stamp-red);
  flex-shrink: 0;
}
.faq-list details[open] summary::after { content: "–"; }
.faq-list details[open] { border-color: var(--rule); }
.faq-list .faq-body { padding: 0 1.25rem 1.25rem; color: var(--ink-soft); }

/* ---- Curriculum ---- */
.module {
  border: 2px solid var(--rule);
  background: var(--paper-card);
  margin-bottom: 1.5rem;
}
.module-head {
  padding: 1.25rem 1.5rem;
  background: var(--paper-deep);
  border-bottom: 2px solid var(--rule);
  display: flex;
  gap: 1rem;
  align-items: baseline;
  flex-wrap: wrap;
}
.module-head .mod-no {
  font-family: var(--mono);
  font-weight: 700;
  color: var(--stamp-red);
  letter-spacing: .12em;
}
.module-head h3 { margin: 0; flex: 1; min-width: 200px; }
.module-head .mod-meta { font-family: var(--mono); font-size: .78rem; color: var(--ink-faint); }
.lesson-list { list-style: none; margin: 0; padding: 0; }
.lesson-list li {
  display: flex;
  gap: 1rem;
  padding: .9rem 1.5rem;
  border-bottom: 1px solid var(--rule-soft);
  align-items: baseline;
}
.lesson-list li:last-child { border-bottom: none; }
.lesson-list .les-no { font-family: var(--mono); font-size: .8rem; color: var(--ink-faint); white-space: nowrap; min-width: 3.5rem; }
.lesson-list .les-title { font-weight: 600; }
.lesson-list .les-time { margin-left: auto; font-family: var(--mono); font-size: .78rem; color: var(--ink-faint); white-space: nowrap; }

/* ---- Footer ---- */
.site-footer {
  border-top: 3px double var(--rule);
  background: var(--paper-card);
  margin-top: 3rem;
}
.footer-inner {
  max-width: calc(var(--maxw) + 72px);
  margin: 0 auto;
  padding: 2.5rem var(--pad) 1.5rem;
}
.footer-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(220px, 1fr));
  gap: 2rem;
  margin-bottom: 2rem;
}
.footer-grid h4 {
  font-family: var(--mono);
  font-size: .78rem;
  letter-spacing: .18em;
  text-transform: uppercase;
  margin-bottom: .8rem;
}
.footer-grid ul { list-style: none; margin: 0; padding: 0; }
.footer-grid li { margin-bottom: .4rem; }
.footer-grid a { text-decoration: none; font-size: .95rem; }
.footer-grid a:hover { text-decoration: underline; }
.footer-rev {
  display: flex;
  justify-content: space-between;
  gap: 1rem;
  flex-wrap: wrap;
  border-top: 1px solid var(--rule-soft);
  padding-top: 1.25rem;
  font-family: var(--mono);
  font-size: .75rem;
  color: var(--ink-faint);
  letter-spacing: .04em;
}

/* ---- Reveal on scroll ---- */
.reveal { opacity: 0; transform: translateY(18px); transition: opacity .5s ease, transform .5s ease; }
.reveal.in { opacity: 1; transform: none; }
@media (prefers-reduced-motion: reduce) {
  html { scroll-behavior: auto; }
  .reveal { opacity: 1; transform: none; transition: none; }
  * { animation: none !important; }
}

/* ---- Utility ---- */
.visually-hidden {
  position: absolute !important;
  width: 1px; height: 1px;
  margin: -1px; padding: 0; border: 0;
  clip: rect(0 0 0 0); clip-path: inset(50%);
  overflow: hidden; white-space: nowrap;
}
.two-col {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 2.5rem;
  align-items: start;
}
@media (max-width: 800px) { .two-col { grid-template-columns: 1fr; } }
.checklist { list-style: none; margin: 0; padding: 0; }
.checklist li {
  padding: .5rem 0 .5rem 2rem;
  position: relative;
  border-bottom: 1px dashed var(--rule-soft);
}
.checklist li::before {
  content: "✓";
  position: absolute; left: .25rem;
  color: var(--ok-green);
  font-weight: 700;
}
.skip-link {
  position: absolute;
  left: -9999px;
  top: 0;
  background: var(--ink);
  color: var(--paper);
  padding: .75rem 1.25rem;
  z-index: 100;
  font-family: var(--mono);
}
.skip-link:focus { left: 0; }
:focus-visible { outline: 3px solid var(--rule); outline-offset: 2px; }