:root {
  --ink: #172126;
  --muted: #66767c;
  --paper: #f4f7f6;
  --paper-deep: #e7eeee;
  --panel: rgba(252, 253, 252, 0.94);
  --rule: #c6d2d3;
  --rule-dark: #91a6aa;
  --accent: #6f9fab;
  --accent-dark: #3f6f7b;
  --accent-pale: #d8e9ee;
  --graph: #8eb2bb;
  --graph-strong: #567e88;
  --shadow: 0 10px 28px rgba(29, 54, 61, 0.08);
  --radius: 14px;
  --display: "Arial Narrow", "Aptos Narrow", "Helvetica Neue", Arial, sans-serif;
  --body: Inter, ui-sans-serif, system-ui, -apple-system, BlinkMacSystemFont, "Segoe UI", sans-serif;
  --mono: "SFMono-Regular", Consolas, "Liberation Mono", monospace;
}

* { box-sizing: border-box; }
html { scroll-behavior: smooth; }
body {
  margin: 0;
  min-width: 320px;
  color: var(--ink);
  background:
    radial-gradient(circle at 12% 5%, rgba(111,159,171,.11), transparent 27rem),
    radial-gradient(circle at 92% 18%, rgba(188,218,225,.23), transparent 31rem),
    var(--paper);
  font-family: var(--body);
  line-height: 1.5;
}

.paper-noise {
  position: fixed;
  inset: 0;
  z-index: -1;
  pointer-events: none;
  opacity: .18;
  background-image:
    repeating-linear-gradient(0deg, rgba(24,49,56,.025) 0, rgba(24,49,56,.025) 1px, transparent 1px, transparent 4px),
    repeating-linear-gradient(90deg, rgba(255,255,255,.35) 0, rgba(255,255,255,.35) 1px, transparent 1px, transparent 7px);
  mix-blend-mode: multiply;
}

.site-header,
.site-footer {
  width: min(1520px, calc(100% - 40px));
  margin-inline: auto;
}
.site-header {
  display: flex;
  align-items: center;
  padding: 20px 0 16px;
  border-bottom: 1px solid var(--rule);
}
.brand {
  display: inline-flex;
  gap: 11px;
  align-items: center;
  color: inherit;
  text-decoration: none;
}
.brand img { width: 42px; height: 42px; }
.brand strong, .brand small { display: block; }
.brand strong {
  font-family: var(--display);
  text-transform: uppercase;
  letter-spacing: .09em;
  font-size: 15px;
}
.brand small { color: var(--muted); font-size: 12px; letter-spacing: .065em; }

.shell {
  width: min(1520px, calc(100% - 40px));
  margin: 0 auto;
  padding: 38px 0 44px;
}
.hero { margin-bottom: 26px; max-width: 940px; }
.eyebrow, .utility-line, .note-kicker {
  font-family: var(--mono);
  letter-spacing: .075em;
  text-transform: uppercase;
}
.eyebrow { margin: 0 0 7px; font-size: 10px; color: var(--accent-dark); }
.hero h1 {
  margin: 0;
  font-family: var(--display);
  font-size: clamp(38px, 5vw, 58px);
  line-height: .98;
  letter-spacing: -.035em;
  text-transform: none;
  font-weight: 800;
}
.tool-subtitle {
  margin: 8px 0 0;
  color: #46575c;
  font-size: clamp(15px, 1.4vw, 18px);
  font-weight: 600;
}
.utility-line { margin: 9px 0 0; color: var(--muted); font-size: 10px; }
.lede { max-width: 810px; margin: 17px 0 0; color: #536268; font-size: 14px; }

.panel {
  background: var(--panel);
  border: 1px solid var(--rule);
  border-radius: var(--radius);
  box-shadow: var(--shadow);
  backdrop-filter: blur(2px);
}
.workspace {
  display: grid;
  grid-template-columns: minmax(390px, 470px) minmax(0, 1fr);
  gap: 20px;
  align-items: stretch;
}
.control-panel, .drawing-panel, .results { padding: 22px; }
.section-heading { display: flex; gap: 12px; align-items: flex-start; margin-bottom: 20px; }
.section-heading.compact { margin-bottom: 12px; }
.drawing-heading { justify-content: space-between; align-items: center; gap: 18px; }
.heading-copy { display: flex; gap: 12px; align-items: flex-start; min-width: 0; }
.report-button { flex: 0 0 auto; padding-inline: 15px; background: var(--accent-pale); border-color: var(--accent); color: var(--ink); }
.report-button:hover { background: #c7e0e7; }
#copyBtn, #reportBtn { text-transform: none; }
.section-heading h2 {
  margin: 0 0 2px;
  font: 800 clamp(18px, 1.8vw, 25px)/1.05 var(--display);
  text-transform: uppercase;
  letter-spacing: -.01em;
}
.section-heading p { margin: 0; color: var(--muted); font-size: 12px; }
.step {
  flex: 0 0 28px;
  width: 28px;
  height: 28px;
  display: grid;
  place-items: center;
  background: var(--ink);
  color: white;
  border-radius: 50%;
  font: 700 11px/1 var(--mono);
}

.field-label {
  display: block;
  margin: 0 0 8px;
  color: var(--muted);
  font: 700 10px/1.2 var(--mono);
  text-transform: uppercase;
  letter-spacing: .07em;
}
.select-control, .number-input {
  width: 100%;
  color: var(--ink);
  background: #fbfcfc;
  border: 1px solid var(--rule-dark);
  border-radius: 8px;
  font: 700 15px/1 var(--mono);
  outline: none;
  transition: border-color .15s ease, box-shadow .15s ease, background .15s ease;
}
.select-control { padding: 13px 42px 13px 13px; margin-bottom: 18px; }
.number-input { min-width: 0; padding: 13px 48px 13px 14px; font-size: 16px; }
.select-control:focus, .number-input:focus {
  border-color: var(--accent-dark);
  background: white;
  box-shadow: 0 0 0 3px rgba(111,159,171,.18);
}
.unit-row { margin-bottom: 18px; }
.segmented {
  display: grid;
  grid-template-columns: repeat(5, 1fr);
  border: 1px solid var(--rule-dark);
  border-radius: 8px;
  overflow: hidden;
}
.segmented button {
  appearance: none;
  border: 0;
  border-right: 1px solid var(--rule);
  padding: 10px 6px;
  background: #f8fbfb;
  color: var(--muted);
  cursor: pointer;
  font: 700 12px/1 var(--mono);
}
.segmented button:last-child { border-right: 0; }
.segmented button:hover { background: var(--accent-pale); color: var(--ink); }
.segmented button.active { background: var(--ink); color: white; }

.driver-field { padding: 14px 0 17px; border-top: 1px solid var(--rule); }
.driver-head {
  display: grid;
  grid-template-columns: minmax(0, 1fr) minmax(160px, 190px);
  gap: 16px;
  align-items: end;
  margin-bottom: 10px;
}
.driver-title strong, .driver-title small { display: block; }
.driver-title strong { font: 800 17px/1.1 var(--display); text-transform: uppercase; }
.driver-title small { margin-top: 4px; color: var(--muted); font-size: 11px; }
.input-with-unit { position: relative; min-width: 160px; }
.input-with-unit .number-input { text-align: right; }
.input-unit {
  position: absolute;
  right: 12px;
  top: 50%;
  transform: translateY(-50%);
  color: var(--muted);
  font: 700 10px/1 var(--mono);
  pointer-events: none;
}
input[type="range"] { width: 100%; height: 25px; margin: 0; background: transparent; accent-color: var(--accent-dark); cursor: ew-resize; }
input[type="range"]::-webkit-slider-runnable-track {
  height: 5px;
  border-radius: 999px;
  background: linear-gradient(90deg, var(--accent-pale), var(--accent-dark));
  box-shadow: inset 0 0 0 1px rgba(32,65,73,.16);
}
input[type="range"]::-webkit-slider-thumb {
  -webkit-appearance: none;
  width: 20px;
  height: 20px;
  margin-top: -7.5px;
  border: 2px solid white;
  border-radius: 50%;
  background: var(--ink);
  box-shadow: 0 1px 4px rgba(0,0,0,.25);
}
.range-labels { display: flex; justify-content: space-between; color: var(--muted); font: 10px/1 var(--mono); }
.button-row { display: grid; grid-template-columns: 1.2fr .8fr; gap: 10px; margin-top: 8px; }
.button {
  appearance: none;
  border: 1px solid var(--rule-dark);
  border-radius: 8px;
  background: #f8fbfb;
  color: var(--ink);
  padding: 12px 11px;
  cursor: pointer;
  font: 800 11px/1.15 var(--display);
  text-transform: uppercase;
  letter-spacing: .025em;
}
.button:hover { transform: translateY(-1px); background: var(--accent-pale); }
.button.primary { color: white; background: var(--accent-dark); border-color: #315b65; }
.error-box {
  margin-top: 14px;
  padding: 11px 12px;
  background: #f4e2df;
  border: 1px solid #c98c83;
  border-radius: 8px;
  color: #713c34;
  font-size: 12px;
}
.construction-note {
  margin-top: 20px;
  padding: 15px;
  background: rgba(216,233,238,.42);
  border-radius: 9px;
  border: 1px dashed var(--rule-dark);
}
.construction-note h3 { margin: 0 0 7px; font: 800 14px/1 var(--display); text-transform: uppercase; }
.construction-note p { margin: 0; font-size: 12px; color: #56666b; }

.drawing-panel { min-height: 680px; display: flex; flex-direction: column; }
.canvas-wrap {
  position: relative;
  min-height: 555px;
  flex: 1;
  overflow: hidden;
  border: 1px solid #a9bec3;
  border-radius: 10px;
  background-color: #f6f9f7;
  background-image:
    linear-gradient(rgba(87,126,136,.12) 1px, transparent 1px),
    linear-gradient(90deg, rgba(87,126,136,.12) 1px, transparent 1px),
    linear-gradient(rgba(87,126,136,.24) 1px, transparent 1px),
    linear-gradient(90deg, rgba(87,126,136,.24) 1px, transparent 1px);
  background-size: 18px 18px, 18px 18px, 90px 90px, 90px 90px;
  box-shadow: inset 0 0 42px rgba(52,85,93,.055);
}
#arcCanvas { display: block; width: 100%; height: 100%; min-height: 555px; }
.canvas-legend { display: flex; flex-wrap: wrap; gap: 17px; margin-top: 11px; color: var(--muted); font-size: 11px; }
.canvas-legend span { display: inline-flex; gap: 7px; align-items: center; }
.line { width: 24px; height: 0; border-top: 2px solid; display: inline-block; }
.arc-line { border-color: var(--accent-dark); border-top-width: 4px; }
.dim-line { border-color: var(--ink); border-top-style: dashed; }
.center-line { border-color: var(--graph-strong); }

.results { margin-top: 20px; }
.result-grid { display: grid; grid-template-columns: repeat(auto-fit, minmax(180px, 1fr)); gap: 10px; }
.result-card {
  padding: 15px 14px 13px;
  min-height: 112px;
  border: 1px solid var(--rule);
  border-radius: 9px;
  background: #f9fbfa;
  overflow: hidden;
}
.result-card span, .result-card strong, .result-card small { display: block; }
.result-card span { color: var(--muted); min-height: 27px; font: 700 10px/1.25 var(--mono); text-transform: uppercase; letter-spacing: .05em; }
.result-card strong { margin: 7px 0 5px; font: 900 clamp(18px, 1.45vw, 25px)/1 var(--display); white-space: nowrap; font-variant-numeric: tabular-nums; }
.result-card small { color: var(--muted); font-size: 10px; }

.guidance-grid { display: grid; grid-template-columns: repeat(3, 1fr); gap: 20px; margin-top: 20px; }
.note-card { padding: 21px; }
.note-kicker { color: var(--accent-dark); font-size: 10px; }
.note-card h2 { margin: 7px 0 9px; font: 800 20px/1.05 var(--display); text-transform: uppercase; }
.note-card p { margin: 0; color: #59676b; font-size: 13px; }
.formula-reference { margin-top: 20px; overflow: hidden; padding: 0; }
.formula-strip { display: grid; grid-template-columns: repeat(5, 1fr); gap: 0; overflow: hidden; }
.formula-strip div { padding: 17px; border-right: 1px solid var(--rule); }
.formula-strip div:last-child { border-right: 0; }
.formula-strip span, .formula-strip strong { display: block; }
.formula-strip span { color: var(--muted); font: 700 10px/1 var(--mono); text-transform: uppercase; }
.formula-strip strong { margin-top: 6px; font: 700 14px/1.2 var(--mono); }
.formula-note { margin: 0; padding: 13px 17px 15px; border-top: 1px solid var(--rule); color: var(--muted); font-size: 12px; line-height: 1.5; }
.formula-note strong { color: var(--ink); }

.site-footer {
  display: flex;
  justify-content: space-between;
  gap: 24px;
  padding: 20px 0 32px;
  border-top: 1px solid var(--rule);
  color: var(--muted);
  font-size: 11px;
}

@media (max-width: 1180px) {
  .workspace { grid-template-columns: minmax(370px, 420px) minmax(0, 1fr); }
  .drawing-panel { min-height: 610px; }
  .canvas-wrap, #arcCanvas { min-height: 490px; }
}
@media (max-width: 900px) {
  .workspace { grid-template-columns: 1fr; }
  .drawing-panel { min-height: 620px; }
  .canvas-wrap, #arcCanvas { min-height: 510px; }
  .guidance-grid { grid-template-columns: 1fr; }
  .formula-strip { grid-template-columns: 1fr 1fr; }
  .formula-strip div:nth-child(2) { border-right: 0; }
  .formula-strip div:nth-child(-n+2) { border-bottom: 1px solid var(--rule); }
}
@media (max-width: 640px) {
  .site-header, .site-footer, .shell { width: min(100% - 24px, 1520px); }
  .shell { padding-top: 30px; }
  .control-panel, .drawing-panel, .results { padding: 16px; }
  .drawing-panel { min-height: 530px; }
  .canvas-wrap, #arcCanvas { min-height: 440px; }
  .driver-head { grid-template-columns: 1fr; gap: 9px; }
  .input-with-unit { width: 100%; min-width: 0; }
  .number-input { font-size: 17px; }
  .button-row { grid-template-columns: 1fr; }
  .drawing-heading { align-items: flex-start; }
  .drawing-heading .report-button { width: auto; }
  .formula-strip { grid-template-columns: 1fr; }
  .formula-strip div { border-right: 0; border-bottom: 1px solid var(--rule); }
  .formula-strip div:last-child { border-bottom: 0; }
  .site-footer { flex-direction: column; }
}
@media (max-width: 520px) {
  .drawing-heading { flex-direction: column; }
  .drawing-heading .report-button { width: 100%; }
}
@media (max-width: 430px) {
  .result-grid { grid-template-columns: 1fr; }
  .canvas-wrap, #arcCanvas { min-height: 400px; }
}