:root {
  --paper: #f6f2e7;
  --paper-raised: #fbf8f0;
  --paper-sunken: #efe9d8;
  --grid-line: rgba(30, 77, 140, 0.09);
  --border: #d8cfb4;
  --border-strong: #b7ab84;
  --ink: #221f1a;
  --ink-soft: #514a3d;
  --ink-mute: #7d735d;
  --ink-faint: #a89c80;

  --blue: #1e4d8c;
  --blue-fill: rgba(30, 77, 140, 0.1);
  --blue-fill-strong: rgba(30, 77, 140, 0.2);
  --red: #b03a2e;
  --red-fill: rgba(176, 58, 46, 0.1);
  --green: #2f6b4f;
  --green-fill: rgba(47, 107, 79, 0.1);

  --font-sans: "Iowan Old Style", "Palatino Linotype", Palatino, "Georgia", "Segoe UI", serif;
  --font-ui: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, Helvetica, Arial, sans-serif;
  --font-mono: ui-monospace, "SF Mono", "Cascadia Code", "Fira Code", Menlo, Consolas, monospace;
}

* {
  box-sizing: border-box;
  margin: 0;
  padding: 0;
}

body {
  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: 24px 24px;
  color: var(--ink);
  font-family: var(--font-ui);
  font-size: 1.0625rem;
  line-height: 1.68;
  -webkit-font-smoothing: antialiased;
  overflow-x: hidden;
}

a { color: var(--blue); }

.site-header {
  border-bottom: 1px solid var(--border-strong);
  background: rgba(246, 242, 231, 0.9);
  backdrop-filter: blur(8px);
  -webkit-backdrop-filter: blur(8px);
  position: sticky;
  top: 0;
  z-index: 100;
}

.header-inner {
  max-width: 1080px;
  margin: 0 auto;
  padding: 1rem 1.5rem;
  display: flex;
  justify-content: space-between;
  align-items: center;
}

.brand-link {
  color: var(--ink-soft);
  text-decoration: none;
  font-family: var(--font-mono);
  font-size: 0.875rem;
  letter-spacing: -0.02em;
}

.brand-link:hover { color: var(--ink); }

.lang-switch {
  display: inline-flex;
  gap: 0.5rem;
  font-family: var(--font-mono);
  font-size: 0.8125rem;
}

.lang-switch a {
  color: var(--ink-mute);
  text-decoration: none;
  padding: 0.25rem 0.5rem;
  border-radius: 3px;
  border: 1px solid transparent;
  transition: all 0.15s ease;
}

.lang-switch a.active {
  color: var(--blue);
  border-color: var(--border-strong);
  background: var(--paper-raised);
}

.lang-switch a:hover:not(.active) { color: var(--ink); }

.container {
  max-width: 1080px;
  margin: 0 auto;
  padding: 3rem 1.5rem 6rem;
}

.hero { margin-bottom: 3.5rem; }

.kicker {
  font-family: var(--font-mono);
  font-size: 0.8125rem;
  text-transform: uppercase;
  letter-spacing: 0.1em;
  color: var(--red);
  margin-bottom: 1rem;
  display: inline-block;
}

h1 {
  font-family: var(--font-sans);
  font-size: 2.75rem;
  line-height: 1.12;
  font-weight: 700;
  letter-spacing: -0.01em;
  margin-bottom: 1.5rem;
  color: var(--ink);
}

.lead {
  font-size: 1.1875rem;
  line-height: 1.62;
  color: var(--ink-soft);
  max-width: 800px;
  margin-bottom: 2.5rem;
}

.metric-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(220px, 1fr));
  gap: 1rem;
  margin: 2.5rem 0;
}

.metric-card {
  background: var(--paper-raised);
  border: 1px solid var(--border);
  border-radius: 3px;
  padding: 1.25rem;
  position: relative;
}

.metric-card::before {
  content: "";
  position: absolute;
  top: 0.6rem;
  bottom: 0.6rem;
  left: 0;
  width: 3px;
  background: var(--blue);
}

.metric-card.red::before { background: var(--red); }
.metric-card.green::before { background: var(--green); }

.metric-value {
  font-family: var(--font-mono);
  font-size: 1.75rem;
  font-weight: 700;
  line-height: 1.2;
  color: var(--ink);
  margin-bottom: 0.4rem;
}

.metric-label {
  font-size: 0.875rem;
  color: var(--ink-mute);
  line-height: 1.42;
}

/* Instrument */
.instrument {
  background: var(--paper-raised);
  border: 1px solid var(--border-strong);
  border-radius: 4px;
  padding: 2rem;
  margin: 3rem 0 4rem;
}

.section-header { margin-bottom: 1.75rem; }

.section-title {
  font-family: var(--font-sans);
  font-size: 1.5rem;
  font-weight: 700;
  letter-spacing: -0.01em;
  margin-bottom: 0.5rem;
  color: var(--ink);
}

.section-subtitle {
  color: var(--ink-soft);
  font-size: 0.9375rem;
  max-width: 720px;
}

.instrument-grid {
  display: grid;
  grid-template-columns: minmax(260px, 1fr) 1.15fr;
  gap: 2rem;
  align-items: start;
}

@media (max-width: 860px) {
  .instrument-grid { grid-template-columns: 1fr; }
}

.fold-diagram-wrap {
  background: var(--paper);
  border: 1px solid var(--border);
  border-radius: 4px;
  padding: 1rem;
  display: flex;
  align-items: center;
  justify-content: center;
}

.fold-diagram-wrap svg { width: 100%; height: auto; display: block; }

.fold-rect {
  fill: var(--paper-raised);
  stroke: var(--ink-faint);
  stroke-width: 1.4;
  transition: fill 0.15s ease, stroke 0.15s ease;
  cursor: pointer;
}

.fold-rect:focus-visible {
  outline: 2px solid var(--blue);
  outline-offset: 2px;
}

.fold-rect.selected {
  fill: var(--blue-fill-strong);
  stroke: var(--blue);
  stroke-width: 2.4;
}

.fold-rect.ancestor {
  fill: transparent;
  stroke: var(--border-strong);
}

.fold-label {
  font-family: var(--font-mono);
  fill: var(--ink-soft);
  pointer-events: none;
}

.fold-label.selected { fill: var(--blue); font-weight: 700; }

.fold-cut-line {
  stroke: var(--red);
  stroke-width: 1;
  stroke-dasharray: 4 3;
  opacity: 0.55;
}

.stepper-row {
  display: flex;
  flex-wrap: wrap;
  gap: 0.35rem;
  margin: 1.25rem 0 1.5rem;
}

.btn-step {
  background: var(--paper);
  border: 1px solid var(--border-strong);
  color: var(--ink-soft);
  font-family: var(--font-mono);
  font-size: 0.8125rem;
  padding: 0.4rem 0.7rem;
  border-radius: 3px;
  cursor: pointer;
  transition: all 0.15s ease;
}

.btn-step:hover { border-color: var(--blue); color: var(--ink); }

.btn-step.active {
  background: var(--blue-fill);
  border-color: var(--blue);
  color: var(--blue);
  font-weight: 700;
}

.readout-panel {
  display: flex;
  flex-direction: column;
  gap: 1.25rem;
}

.readout-card {
  background: var(--paper);
  border: 1px solid var(--border);
  border-radius: 4px;
  padding: 1.25rem 1.4rem;
}

.readout-title {
  font-family: var(--font-mono);
  font-size: 0.75rem;
  text-transform: uppercase;
  letter-spacing: 0.08em;
  color: var(--ink-mute);
  margin-bottom: 0.6rem;
}

.readout-dims {
  font-family: var(--font-mono);
  font-size: 1.75rem;
  font-weight: 700;
  color: var(--ink);
  margin-bottom: 0.3rem;
}

.readout-sub {
  font-size: 0.9375rem;
  color: var(--ink-soft);
}

.readout-compare {
  font-size: 0.875rem;
  color: var(--ink-mute);
  margin-top: 0.5rem;
  font-style: italic;
}

.field-row {
  display: flex;
  align-items: center;
  gap: 0.6rem;
  flex-wrap: wrap;
  margin-top: 0.75rem;
}

.field-row label {
  font-size: 0.8125rem;
  color: var(--ink-mute);
  font-family: var(--font-mono);
}

.num-input {
  background: var(--paper-raised);
  border: 1px solid var(--border-strong);
  border-radius: 3px;
  padding: 0.4rem 0.6rem;
  color: var(--ink);
  font-family: var(--font-mono);
  font-size: 0.9375rem;
  width: 6rem;
  outline: none;
}

.num-input:focus { border-color: var(--blue); }

.weight-result {
  font-family: var(--font-mono);
  font-size: 1.375rem;
  font-weight: 700;
  color: var(--blue);
  margin-top: 0.6rem;
}

/* Zoom calculator + rectangle checker */
.tool-pair {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 1.5rem;
  margin-top: 1rem;
}

@media (max-width: 720px) {
  .tool-pair { grid-template-columns: 1fr; }
}

.tool-box {
  background: var(--paper);
  border: 1px solid var(--border);
  border-radius: 4px;
  padding: 1.4rem;
}

.tool-box h3 {
  font-family: var(--font-sans);
  font-size: 1.125rem;
  margin-bottom: 0.75rem;
  color: var(--ink);
}

.select-row {
  display: flex;
  align-items: center;
  gap: 0.6rem;
  flex-wrap: wrap;
  margin-bottom: 0.75rem;
}

select, input[type="text"] {
  background: var(--paper-raised);
  border: 1px solid var(--border-strong);
  border-radius: 3px;
  padding: 0.4rem 0.6rem;
  color: var(--ink);
  font-family: var(--font-mono);
  font-size: 0.9375rem;
  outline: none;
}

select:focus, input[type="text"]:focus { border-color: var(--blue); }

.zoom-result {
  font-family: var(--font-mono);
  font-size: 1.75rem;
  font-weight: 700;
  color: var(--blue);
  margin-top: 0.5rem;
}

.zoom-note {
  font-size: 0.8125rem;
  color: var(--ink-mute);
  margin-top: 0.4rem;
}

.preset-row {
  display: flex;
  flex-wrap: wrap;
  gap: 0.4rem;
  margin-bottom: 0.75rem;
}

.btn-preset-mini {
  background: var(--paper-raised);
  border: 1px solid var(--border);
  color: var(--ink-soft);
  font-family: var(--font-mono);
  font-size: 0.75rem;
  padding: 0.3rem 0.55rem;
  border-radius: 3px;
  cursor: pointer;
}

.btn-preset-mini:hover { border-color: var(--blue); color: var(--ink); }

.verdict {
  margin-top: 0.75rem;
  padding: 0.75rem 1rem;
  border-radius: 3px;
  font-size: 0.9375rem;
  font-family: var(--font-mono);
}

.verdict.conform {
  background: var(--green-fill);
  color: var(--green);
  border: 1px solid var(--green);
}

.verdict.neconform {
  background: var(--red-fill);
  color: var(--red);
  border: 1px solid var(--red);
}

/* Prose */
.prose { margin: 3.5rem 0; }

.prose h2 {
  font-family: var(--font-sans);
  font-size: 1.75rem;
  font-weight: 700;
  letter-spacing: -0.01em;
  margin: 2.5rem 0 1rem;
  color: var(--ink);
}

.prose p { margin-bottom: 1.5rem; color: var(--ink-soft); }
.prose p strong { color: var(--ink); }
.prose ul, .prose ol { margin: 1rem 0 1.5rem 1.5rem; color: var(--ink-soft); }
.prose li { margin-bottom: 0.5rem; }

.callout {
  background: var(--paper-raised);
  border: 1px solid var(--border);
  border-left: 3px solid var(--red);
  border-radius: 0 4px 4px 0;
  padding: 1.25rem 1.5rem;
  margin: 2rem 0;
}

.callout-title {
  font-family: var(--font-mono);
  font-size: 0.8125rem;
  text-transform: uppercase;
  color: var(--red);
  margin-bottom: 0.5rem;
  font-weight: 600;
}

.callout p { margin-bottom: 0; font-size: 0.9375rem; color: var(--ink-soft); }

.math-display {
  font-family: var(--font-mono);
  font-size: 1.25rem;
  text-align: center;
  margin: 0.75rem 0 1rem;
  color: var(--blue);
  font-weight: 600;
  letter-spacing: 0.03em;
}

.table-wrapper {
  overflow-x: auto;
  margin: 1.5rem 0;
  border: 1px solid var(--border);
  border-radius: 4px;
}

table { width: 100%; border-collapse: collapse; font-size: 0.875rem; text-align: left; }

th {
  background: var(--paper-sunken);
  color: var(--ink-soft);
  font-family: var(--font-mono);
  font-size: 0.75rem;
  text-transform: uppercase;
  letter-spacing: 0.04em;
  padding: 0.7rem 0.9rem;
  border-bottom: 1px solid var(--border);
}

td { padding: 0.7rem 0.9rem; border-bottom: 1px solid var(--border); color: var(--ink); }
tr:last-child td { border-bottom: none; }
.mono { font-family: var(--font-mono); }

/* Method & Footer */
.method-box {
  background: var(--paper-raised);
  border: 1px solid var(--border);
  border-radius: 4px;
  padding: 1.75rem;
  margin: 4rem 0 2rem;
}

.method-title { font-family: var(--font-sans); font-size: 1.125rem; font-weight: 700; margin-bottom: 0.75rem; color: var(--ink); }
.method-box p { font-size: 0.875rem; color: var(--ink-mute); line-height: 1.6; margin-bottom: 0.75rem; }
.method-box p:last-child { margin-bottom: 0; }

.site-footer {
  border-top: 1px solid var(--border-strong);
  padding: 2.5rem 1.5rem;
  text-align: center;
  color: var(--ink-mute);
  font-size: 0.875rem;
}

.footer-links { display: flex; justify-content: center; gap: 1.5rem; margin-bottom: 1rem; flex-wrap: wrap; }
.footer-links a { color: var(--ink-soft); text-decoration: none; }
.footer-links a:hover { color: var(--ink); }

@media (prefers-reduced-motion: reduce) {
  * {
    animation-duration: 0.01ms !important;
    animation-iteration-count: 1 !important;
    transition-duration: 0.01ms !important;
    scroll-behavior: auto !important;
  }
}

@media (max-width: 640px) {
  .container { padding: 1.5rem 1rem 4rem; }
  h1 { font-size: 1.75rem; }
  .lead { font-size: 1.0625rem; }
  .instrument { padding: 1.25rem; margin: 2rem 0; }
  .metric-grid { grid-template-columns: 1fr; }
  .header-inner { padding: 0.75rem 1rem; }
  .readout-dims { font-size: 1.5rem; }
}