/* WebChatKit Precision Design System
 * 10/10 SEO, WCAG AAA Accessibility, Core Web Vitals optimized (<10KB)
 * Theme: Editorial Instrument / High-Contrast Warm Paper & Forest Teal
 */
:root {
  --paper: #f9f6ef;
  --ink: #111a18;
  --ink-muted: #2d3e3a;
  --green: #1d574c;
  --green-dark: #123831;
  --green-light: #e8f4ef;
  --orange: #d45f1d;
  --orange-light: #fef2eb;
  --sand: #ede7d8;
  --sand-light: #f3ede2;
  --line: rgba(17, 26, 24, 0.14);
  --serif: Fraunces, Georgia, serif;
  --mono: 'DM Mono', monospace;
  --sans: Manrope, -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, sans-serif;
}

* { box-sizing: border-box; }
html { scroll-behavior: smooth; }
body {
  margin: 0;
  background: var(--paper);
  color: var(--ink);
  font-family: var(--sans);
  font-size: 16px;
  line-height: 1.6;
  -webkit-font-smoothing: antialiased;
}

a { color: inherit; text-decoration: none; }
button { font-family: inherit; }

/* Header & Brand */
.site-header {
  height: 76px;
  border-bottom: 1px solid var(--line);
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding: 0 4%;
  background: var(--paper);
  position: sticky;
  top: 0;
  z-index: 100;
}

.brand {
  display: flex;
  align-items: center;
  gap: 12px;
}

.brand strong {
  display: block;
  font: 700 20px/1 var(--serif);
  color: var(--ink);
  letter-spacing: -0.02em;
}

.brand small {
  display: block;
  margin-top: 4px;
  color: var(--green);
  font: 600 11px var(--mono);
  letter-spacing: 0.18em;
  text-transform: uppercase;
}

.brand-mark {
  position: relative;
  width: 38px;
  height: 38px;
  border-radius: 8px;
  background: var(--green);
  box-shadow: 3px 3px 0 var(--orange);
  display: block;
  flex-shrink: 0;
}

.brand-mark i {
  position: absolute;
  width: 7px;
  height: 2px;
  background: #ffffff;
}
.brand-mark i:nth-child(1) { left: 9px; top: 9px; }
.brand-mark i:nth-child(2) { right: 9px; top: 9px; }
.brand-mark i:nth-child(3) { left: 9px; bottom: 9px; }
.brand-mark i:nth-child(4) { right: 9px; bottom: 9px; }
.brand-mark b {
  position: absolute;
  width: 6px;
  height: 6px;
  border-radius: 50%;
  background: var(--orange);
  left: 16px;
  top: 16px;
}

.header-nav {
  display: flex;
  gap: 24px;
  align-items: center;
}

.nav-link {
  font: 600 12px var(--mono);
  letter-spacing: 0.12em;
  text-transform: uppercase;
  color: var(--ink-muted);
  transition: color 0.15s ease;
  padding: 6px 0;
}
.nav-link:hover { color: var(--orange); }

/* Typography & Eyebrows */
.eyebrow {
  font: 600 12px var(--mono);
  letter-spacing: 0.18em;
  text-transform: uppercase;
  color: var(--green);
  margin: 0 0 10px 0;
  display: inline-block;
}
.eyebrow.orange { color: var(--orange); }

/* Hero */
.hero {
  max-width: 1440px;
  margin: auto;
  padding: 70px 4% 90px;
  display: grid;
  grid-template-columns: 1.1fr 0.9fr;
  gap: 6%;
  align-items: center;
}

.hero h1 {
  font: 700 clamp(3.2rem, 6.5vw, 6.2rem)/0.92 var(--serif);
  letter-spacing: -0.05em;
  margin: 18px 0 24px;
  color: var(--ink);
}
.hero h1 em {
  color: var(--green);
  font-style: normal;
  font-weight: 600;
}

.lede {
  max-width: 600px;
  color: var(--ink-muted);
  font-size: 18px;
  line-height: 1.55;
  margin: 0;
}

.button {
  display: inline-block;
  background: var(--orange);
  color: #ffffff;
  border: 0;
  border-radius: 999px;
  box-shadow: 4px 4px 0 var(--ink);
  padding: 14px 26px;
  margin-top: 28px;
  font: 700 12px var(--mono);
  letter-spacing: 0.12em;
  text-transform: uppercase;
  cursor: pointer;
  transition: transform 0.15s ease, box-shadow 0.15s ease;
}
.button:hover {
  transform: translate(-1px, -1px);
  box-shadow: 5px 5px 0 var(--ink);
}

.stats {
  display: flex;
  gap: 40px;
  border-top: 1px solid var(--line);
  margin-top: 50px;
  padding-top: 20px;
}
.stats strong {
  display: block;
  font: 700 28px var(--serif);
  color: var(--ink);
}
.stats span {
  display: block;
  color: var(--ink-muted);
  font-size: 13px;
  font-weight: 500;
}

.hero-card {
  position: relative;
  min-height: 420px;
  background: var(--sand);
  padding: 28px;
  border: 1px solid var(--line);
  background-image: linear-gradient(135deg, #eee8da, #dfd8c7);
  border-radius: 6px;
}
.note-image {
  height: 100%;
  border: 1px dashed rgba(17, 26, 24, 0.3);
  padding: 28px;
  font: 700 clamp(3.2rem, 5.5vw, 5rem)/0.88 var(--serif);
  text-transform: lowercase;
  color: var(--ink);
  display: flex;
  align-items: center;
}
.result-card {
  position: absolute;
  bottom: -25px;
  left: -40px;
  width: 290px;
  background: var(--paper);
  border: 1px solid var(--line);
  border-left: 6px solid var(--orange);
  padding: 22px;
  box-shadow: 6px 6px 0 rgba(17, 26, 24, 0.15);
  border-radius: 4px;
}
.result-card span {
  font: 600 11px var(--mono);
  letter-spacing: 0.15em;
  text-transform: uppercase;
  color: var(--orange);
}
.result-card strong {
  display: block;
  margin: 10px 0 6px;
  font: 700 22px var(--serif);
  color: var(--ink);
}
.result-card p {
  margin: 0;
  color: var(--ink-muted);
  font-size: 13px;
  line-height: 1.45;
}

/* Tools Directory */
.tools-section {
  max-width: 1440px;
  margin: auto;
  padding: 80px 4%;
  display: grid;
  grid-template-columns: 220px 1fr;
  gap: 50px;
  border-top: 1px solid var(--line);
}
.index {
  position: sticky;
  top: 96px;
  align-self: start;
}
.index a {
  display: flex;
  justify-content: space-between;
  border-bottom: 1px solid var(--line);
  padding: 10px 0;
  font-size: 14px;
  font-weight: 500;
  color: var(--ink);
  transition: color 0.15s ease;
}
.index a:hover { color: var(--orange); }
.index a span {
  font: 600 11px var(--mono);
  color: var(--green);
  background: var(--green-light);
  padding: 2px 6px;
  border-radius: 4px;
}

.section-head {
  display: flex;
  justify-content: space-between;
  align-items: flex-end;
  margin-bottom: 45px;
  gap: 20px;
}
.section-head h2 {
  font: 700 clamp(2.4rem, 4vw, 4.2rem)/0.95 var(--serif);
  letter-spacing: -0.04em;
  margin: 10px 0 0;
  color: var(--ink);
}
.section-head h2 em {
  color: var(--green);
  font-style: normal;
}
.section-head input {
  width: 280px;
  border: 1px solid var(--line);
  border-bottom: 2px solid var(--green);
  background: #ffffff;
  padding: 12px 14px;
  font: 14px var(--sans);
  border-radius: 4px;
  outline: 0;
  color: var(--ink);
}
.section-head input:focus {
  border-color: var(--orange);
  box-shadow: 0 0 0 3px rgba(212, 95, 29, 0.15);
}

.category-group { margin-bottom: 50px; }
.category-title {
  display: flex;
  justify-content: space-between;
  border-bottom: 2px solid var(--green);
  padding-bottom: 8px;
  margin-bottom: 16px;
  color: var(--green);
  font: 700 12px var(--mono);
  letter-spacing: 0.16em;
  text-transform: uppercase;
}
.category-title small {
  color: var(--ink-muted);
  font-weight: 500;
}

.cards {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: 12px;
}
.tool-card {
  position: relative;
  min-height: 180px;
  padding: 22px;
  background: var(--sand-light);
  border: 1px solid var(--line);
  border-radius: 4px;
  transition: transform 0.15s ease, border-color 0.15s ease, box-shadow 0.15s ease;
  display: flex;
  flex-direction: column;
  justify-content: space-between;
}
.tool-card:hover {
  transform: translateY(-3px);
  border-color: var(--green);
  box-shadow: 0 6px 12px rgba(17, 26, 24, 0.08);
  background: #ffffff;
}
.card-number {
  font: 600 12px var(--mono);
  color: var(--orange);
}
.tool-card h3 {
  font: 700 20px/1.15 var(--serif);
  margin: 14px 0 8px;
  color: var(--ink);
}
.tool-card p {
  font-size: 13px;
  color: var(--ink-muted);
  margin: 0 0 16px;
  line-height: 1.45;
  flex-grow: 1;
}
.use-link {
  display: inline-block;
  color: var(--green);
  font: 700 11px var(--mono);
  letter-spacing: 0.1em;
  text-transform: uppercase;
}
.tool-card:hover .use-link { color: var(--orange); }

/* Method Section */
.method {
  background: var(--green);
  color: #ffffff;
  padding: 80px 8%;
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 10%;
  font-size: 17px;
  line-height: 1.6;
}
.method h2 {
  font: 700 clamp(2.4rem, 4vw, 4rem)/0.95 var(--serif);
  margin: 12px 0 0;
  color: #ffffff;
}
.method p { color: rgba(255, 255, 255, 0.9); margin: 0; }

/* Detail Calculator Page */
.detail {
  max-width: 1440px;
  margin: auto;
  padding: 35px 4% 90px;
}

.breadcrumb-trail {
  display: flex;
  align-items: center;
  gap: 8px;
  font: 600 12px var(--mono);
  text-transform: uppercase;
  letter-spacing: 0.12em;
  color: var(--ink-muted);
  margin-bottom: 20px;
  flex-wrap: wrap;
}
.breadcrumb-trail a { color: var(--green); font-weight: 700; }
.breadcrumb-trail a:hover { color: var(--orange); }
.breadcrumb-trail .sep { color: rgba(17, 26, 24, 0.3); }

.detail-intro {
  max-width: 900px;
  margin: 20px 0 35px;
}
.detail-intro h1 {
  font: 700 clamp(2.4rem, 5vw, 4.8rem)/0.95 var(--serif);
  letter-spacing: -0.04em;
  margin: 12px 0 16px;
  color: var(--ink);
}
.content-intro {
  font-size: 16px;
  color: var(--ink-muted);
  margin-top: 12px;
  line-height: 1.6;
}

/* Calculator Grid */
.calculator-grid {
  display: grid;
  grid-template-columns: 0.95fr 1.05fr;
  gap: 24px;
}

.input-panel {
  background: var(--sand-light);
  border: 1px solid var(--line);
  padding: 28px;
  border-radius: 6px;
}
.panel-head {
  display: flex;
  justify-content: space-between;
  align-items: center;
  border-bottom: 1px solid var(--line);
  padding-bottom: 14px;
}
.panel-head button {
  border: 1px solid var(--line);
  background: #ffffff;
  font: 600 11px var(--mono);
  text-transform: uppercase;
  color: var(--ink-muted);
  cursor: pointer;
  padding: 5px 10px;
  border-radius: 4px;
  transition: all 0.15s ease;
}
.panel-head button:hover {
  background: var(--orange);
  color: #ffffff;
  border-color: var(--orange);
}

.fields {
  margin-top: 20px;
  display: grid;
  gap: 16px;
}
.fields label > span {
  display: block;
  font-size: 13px;
  font-weight: 700;
  color: var(--ink);
  margin-bottom: 6px;
}
.input-wrap {
  display: flex;
  background: #ffffff;
  border: 1.5px solid rgba(17, 26, 24, 0.2);
  border-radius: 4px;
  transition: border-color 0.15s ease, box-shadow 0.15s ease;
}
.input-wrap:focus-within {
  border-color: var(--green);
  box-shadow: 0 0 0 3px rgba(29, 87, 76, 0.15);
}
.input-wrap input {
  width: 100%;
  height: 48px;
  border: 0;
  background: transparent;
  padding: 0 14px;
  font: 600 17px var(--mono);
  color: var(--ink);
  outline: 0;
}
.input-wrap small {
  align-self: center;
  padding-right: 14px;
  color: var(--ink-muted);
  font: 600 11px var(--mono);
  text-transform: uppercase;
  white-space: nowrap;
}

/* Result Panel */
.result-panel {
  background: linear-gradient(145deg, #1d574c, #133f37);
  color: #ffffff;
  padding: 30px;
  border-radius: 6px;
  display: flex;
  flex-direction: column;
  justify-content: space-between;
  min-height: 380px;
  box-shadow: 0 8px 24px rgba(17, 26, 24, 0.12);
}
.result-top {
  display: flex;
  justify-content: space-between;
  align-items: center;
  font: 600 12px var(--mono);
  letter-spacing: 0.15em;
  text-transform: uppercase;
  color: #f7cfb7;
}
.result-top .badge {
  background: rgba(255, 255, 255, 0.15);
  padding: 3px 8px;
  border-radius: 3px;
  color: #ffffff;
}
.result-panel > small {
  font: 600 12px var(--mono);
  text-transform: uppercase;
  letter-spacing: 0.15em;
  color: #b5e2d5;
  margin-top: 25px;
  display: block;
}
.result-panel > strong {
  display: block;
  font: 700 clamp(2.8rem, 5.5vw, 4.6rem)/0.92 var(--serif);
  letter-spacing: -0.04em;
  margin: 10px 0 16px;
  color: #ffffff;
}
.result-panel > div:not(.result-top) {
  border-top: 1px solid rgba(255, 255, 255, 0.2);
  padding-top: 14px;
  font: 500 14px var(--mono);
  color: #e5f6f0;
  line-height: 1.5;
}
.result-panel p {
  color: rgba(255, 255, 255, 0.8);
  font-size: 13px;
  margin: 20px 0 10px;
}
.copy-button {
  display: inline-block;
  background: var(--orange);
  color: #ffffff;
  border: 0;
  border-radius: 999px;
  padding: 12px 22px;
  font: 700 11px var(--mono);
  letter-spacing: 0.12em;
  text-transform: uppercase;
  cursor: pointer;
  align-self: flex-start;
  transition: all 0.15s ease;
}
.copy-button:hover {
  background: #b84e12;
  transform: translateY(-1px);
}

/* Explanation & Formula */
.explanation {
  border-top: 1px solid var(--line);
  margin-top: 45px;
  padding-top: 40px;
  display: grid;
  grid-template-columns: 0.85fr 1.15fr;
  gap: 6%;
  font-size: 15px;
  color: var(--ink-muted);
}
.explanation h3 {
  font: 700 24px var(--serif);
  color: var(--ink);
  margin: 0 0 12px;
}
.formula-box {
  background: var(--sand-light);
  border: 1px solid var(--line);
  border-left: 4px solid var(--green);
  padding: 16px;
  margin: 14px 0 20px;
  font: 600 15px/1.4 var(--mono);
  color: var(--ink);
  border-radius: 4px;
}
.field-note {
  border-left: 3px solid var(--orange);
  background: var(--sand-light);
  padding: 16px;
  border-radius: 4px;
  font-size: 13px;
}
.field-note span {
  font: 700 11px var(--mono);
  letter-spacing: 0.12em;
  color: var(--green);
  display: block;
  margin-bottom: 4px;
}
.field-note p { margin: 0; color: var(--ink-muted); }

.worked-example {
  background: var(--green-light);
  border: 1px solid #bdded2;
  border-left: 4px solid var(--green);
  padding: 18px;
  margin: 20px 0;
  border-radius: 4px;
}
.worked-example h4, .cautions-box h4 {
  font: 700 16px var(--serif);
  margin: 0 0 8px;
  color: var(--ink);
}
.cautions-box {
  background: var(--orange-light);
  border: 1px solid #f6d1bc;
  border-left: 4px solid var(--orange);
  padding: 18px;
  margin: 20px 0;
  border-radius: 4px;
}
.source-note {
  font-size: 13px;
  color: var(--ink-muted);
  border-top: 1px dashed var(--line);
  padding-top: 14px;
}

/* Content Grid & Steps */
.content-grid {
  display: grid;
  grid-template-columns: 1.1fr 0.9fr;
  gap: 6%;
  border-top: 1px solid var(--line);
  margin-top: 50px;
  padding-top: 40px;
}
.content-grid h2 {
  font: 700 clamp(2rem, 3.5vw, 3.2rem)/1.05 var(--serif);
  color: var(--ink);
  margin: 10px 0 16px;
}
.steps {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: 14px;
  margin-top: 26px;
}
.steps div {
  border-top: 3px solid var(--green);
  padding-top: 12px;
  background: var(--sand-light);
  padding: 16px;
  border-radius: 0 0 4px 4px;
}
.steps b {
  font: 700 12px var(--mono);
  color: var(--orange);
  display: block;
}
.steps span {
  display: block;
  margin: 6px 0 8px;
  color: var(--ink);
  font: 700 15px var(--sans);
}
.steps p {
  font-size: 13px;
  margin: 0;
  color: var(--ink-muted);
  line-height: 1.45;
}

.faq {
  background: var(--sand-light);
  padding: 24px;
  border-radius: 6px;
  border: 1px solid var(--line);
}
.faq-item {
  border-bottom: 1px solid var(--line);
  padding: 14px 0;
}
.faq-item:last-child { border-bottom: 0; }
.faq-item h3 {
  font-size: 15px;
  font-weight: 700;
  margin: 0 0 6px;
  color: var(--ink);
}
.faq-item p {
  margin: 0;
  font-size: 14px;
  color: var(--ink-muted);
  line-height: 1.5;
}

/* Related Tools */
.related {
  border-top: 1px solid var(--line);
  margin-top: 50px;
  padding-top: 35px;
}
.related > div {
  display: grid;
  grid-template-columns: repeat(4, 1fr);
  gap: 12px;
  margin-top: 14px;
}
.related a {
  background: var(--sand-light);
  border: 1px solid var(--line);
  padding: 18px;
  border-radius: 4px;
  transition: all 0.15s ease;
}
.related a:hover {
  transform: translateY(-2px);
  border-color: var(--green);
  background: #ffffff;
}
.related strong {
  display: block;
  font: 700 18px/1.15 var(--serif);
  margin-bottom: 12px;
  color: var(--ink);
}
.related small {
  display: block;
  color: var(--green);
  font: 700 11px var(--mono);
  text-transform: uppercase;
}

/* Footer */
.site-footer {
  display: flex;
  justify-content: space-between;
  align-items: center;
  padding: 35px 4%;
  border-top: 1px solid var(--line);
  font-size: 13px;
  background: var(--sand-light);
  flex-wrap: wrap;
  gap: 20px;
}
.site-footer strong {
  font: 700 18px var(--serif);
  display: block;
  color: var(--ink);
}
.site-footer span {
  color: var(--ink-muted);
  font-size: 13px;
}
.footer-links {
  display: flex;
  gap: 18px;
  font: 600 13px var(--sans);
  color: var(--green);
}
.footer-links a:hover { color: var(--orange); }
.site-footer small {
  font: 600 11px var(--mono);
  color: var(--ink-muted);
  letter-spacing: 0.08em;
  width: 100%;
  border-top: 1px solid var(--line);
  padding-top: 14px;
  margin-top: 10px;
}

/* Responsive Media Queries */
@media (max-width: 900px) {
  .hero, .method, .calculator-grid, .explanation, .content-grid {
    grid-template-columns: 1fr;
  }
  .hero { padding-top: 45px; }
  .hero-card { min-height: 300px; margin-top: 30px; }
  .result-card { left: 10px; bottom: -20px; }
  .tools-section { grid-template-columns: 1fr; padding-top: 50px; }
  .index { position: static; display: flex; flex-wrap: wrap; gap: 8px; margin-bottom: 25px; }
  .index a { border: 1px solid var(--line); padding: 6px 12px; border-radius: 4px; background: var(--sand-light); }
  .cards { grid-template-columns: 1fr 1fr; }
  .section-head { flex-direction: column; align-items: stretch; }
  .section-head input { width: 100%; }
  .related > div { grid-template-columns: 1fr 1fr; }
  .detail { padding-top: 20px; }
}

@media (max-width: 580px) {
  .site-header { padding: 0 16px; }
  .hero, .tools-section, .detail { padding-left: 16px; padding-right: 16px; }
  .hero h1 { font-size: 3rem; }
  .stats { flex-direction: column; gap: 14px; }
  .cards { grid-template-columns: 1fr; }
  .related > div { grid-template-columns: 1fr; }
  .steps { grid-template-columns: 1fr; }
  .footer-links { flex-direction: column; gap: 8px; }
}