:root {
  --ink: #122033;
  --muted: #607083;
  --paper: #f4f7fb;
  --card: rgba(255,255,255,0.94);
  --line: #cfd8e4;
  --line-strong: #9fb0c5;
  --blue: #0b5fc6;
  --blue-dark: #083e84;
  --blue-soft: #dbeaff;
  --reflected: #c26324;
  --aggregate: #10233b;
  --danger: #8b2a2a;
  --shadow: 0 12px 30px rgba(15, 38, 70, 0.08);
  --radius: 18px;
  --mono: ui-monospace, SFMono-Regular, Menlo, Monaco, Consolas, "Liberation Mono", monospace;
  --sans: Inter, ui-sans-serif, system-ui, -apple-system, BlinkMacSystemFont, "Segoe UI", Helvetica, Arial, sans-serif;
}

* { box-sizing: border-box; }
html { color-scheme: light; }
body {
  margin: 0;
  color: var(--ink);
  font-family: var(--sans);
  background:
    linear-gradient(rgba(31, 78, 130, 0.045) 1px, transparent 1px),
    linear-gradient(90deg, rgba(31, 78, 130, 0.045) 1px, transparent 1px),
    linear-gradient(rgba(31, 78, 130, 0.075) 1px, transparent 1px),
    linear-gradient(90deg, rgba(31, 78, 130, 0.075) 1px, transparent 1px),
    var(--paper);
  background-size: 24px 24px, 24px 24px, 120px 120px, 120px 120px, auto;
}

button, input, select { font: inherit; }
button { cursor: pointer; }

.app-shell {
  width: min(1440px, calc(100% - 32px));
  margin: 0 auto;
  padding: 28px 0 36px;
}

.tool-header {
  display: flex;
  align-items: flex-start;
  justify-content: space-between;
  gap: 24px;
  padding: 22px 24px 26px;
  border-bottom: 3px solid var(--blue);
  margin-bottom: 18px;
}

.brand-lockup { display: flex; gap: 18px; align-items: center; }
.tool-logo { width: 74px; height: 74px; flex: 0 0 auto; }
.eyebrow {
  text-transform: uppercase;
  letter-spacing: 0.14em;
  font-size: 0.76rem;
  font-weight: 800;
  color: var(--blue-dark);
  margin-bottom: 3px;
}
h1, h2, p { margin-top: 0; }
h1 {
  margin-bottom: 2px;
  font-size: clamp(2.4rem, 5vw, 4.6rem);
  line-height: 0.95;
  letter-spacing: -0.055em;
  font-weight: 850;
}
.subtitle { margin: 7px 0 0; color: var(--muted); font-size: 1.02rem; }
.header-badges { display: flex; flex-wrap: wrap; gap: 8px; justify-content: flex-end; padding-top: 5px; }
.header-badges span {
  border: 1px solid var(--line-strong);
  border-radius: 999px;
  padding: 7px 10px;
  font-size: 0.76rem;
  font-weight: 750;
  background: rgba(255,255,255,.7);
}

.card {
  background: var(--card);
  border: 1px solid var(--line);
  box-shadow: var(--shadow);
  border-radius: var(--radius);
}
.intro-card {
  display: grid;
  grid-template-columns: 1fr auto;
  gap: 28px;
  padding: 22px 24px;
  margin-bottom: 18px;
  align-items: end;
}
.intro-card h2, .card-heading h2, .visual-heading h2, .reference-card h2, .explainer-card h2, .assumptions-card h2 {
  margin: 0 0 7px;
  font-size: 1.32rem;
  letter-spacing: -0.02em;
}
.intro-card p, .card-copy, .visual-heading p, .explainer-card p, .assumptions-card p {
  color: var(--muted);
  line-height: 1.56;
  margin-bottom: 0;
}
.section-number {
  display: block;
  font-family: var(--mono);
  color: var(--blue);
  font-size: .77rem;
  font-weight: 800;
  margin-bottom: 6px;
}

.unit-controls { display: flex; gap: 12px; align-items: end; flex-wrap: wrap; justify-content: flex-end; }
.segmented {
  display: inline-flex;
  padding: 4px;
  border: 1px solid var(--line);
  background: #eef3f8;
  border-radius: 12px;
}
.seg {
  border: 0;
  background: transparent;
  color: var(--muted);
  font-weight: 800;
  padding: 10px 15px;
  border-radius: 9px;
}
.seg.active { background: var(--blue); color: white; box-shadow: 0 3px 10px rgba(11,95,198,.25); }

.calculator-grid {
  display: grid;
  grid-template-columns: minmax(0, 1.05fr) minmax(360px, .95fr);
  gap: 18px;
  margin-bottom: 18px;
}
.input-card, .distance-card, .reference-card, .explainer-card, .assumptions-card { padding: 24px; }
.card-heading { margin-bottom: 20px; }
.primary-inputs {
  display: grid;
  grid-template-columns: minmax(0,1fr) auto minmax(0,1fr);
  gap: 16px;
  align-items: end;
  padding: 20px;
  border: 1px solid var(--line);
  background: linear-gradient(180deg, #f8fbff, #f2f6fb);
  border-radius: 15px;
}
.equals-mark { font-size: 2rem; font-weight: 300; color: var(--blue); padding-bottom: 11px; }
.field { display: block; }
.field > span:first-child {
  display: block;
  font-size: .78rem;
  font-weight: 800;
  color: var(--muted);
  text-transform: uppercase;
  letter-spacing: .065em;
  margin-bottom: 7px;
}
.hero-field input { font-size: 1.55rem; font-weight: 760; }
.input-with-unit {
  display: flex;
  align-items: center;
  min-height: 46px;
  border: 1px solid var(--line-strong);
  border-radius: 11px;
  background: #fff;
  overflow: hidden;
}
.input-with-unit:focus-within { outline: 3px solid rgba(11,95,198,.14); border-color: var(--blue); }
.input-with-unit input {
  min-width: 0;
  flex: 1 1 auto;
  border: 0;
  outline: 0;
  padding: 11px 12px;
  background: transparent;
  color: var(--ink);
}
.input-with-unit > span { padding: 0 12px; color: var(--muted); font-family: var(--mono); font-size: .85rem; }
select {
  width: 100%;
  border: 1px solid var(--line-strong);
  border-radius: 10px;
  background: white;
  color: var(--ink);
  padding: 10px 34px 10px 11px;
}

.length-ftin { display: grid; grid-template-columns: 1fr 1fr; gap: 8px; }
.length-ftin .input-with-unit { min-width: 0; }

.stats-grid {
  display: grid;
  grid-template-columns: repeat(4, minmax(0,1fr));
  gap: 10px;
  margin: 16px 0;
}
.stats-grid.two-col { grid-template-columns: repeat(2, minmax(0,1fr)); }
.stat {
  border: 1px solid var(--line);
  border-radius: 12px;
  padding: 13px;
  min-height: 78px;
  background: #fff;
}
.stat span { display: block; color: var(--muted); font-size: .74rem; font-weight: 750; margin-bottom: 5px; }
.stat strong { font-family: var(--mono); font-size: .94rem; line-height: 1.35; }

.model-settings { margin-top: 12px; border-top: 1px solid var(--line); padding-top: 14px; }
.model-settings summary { color: var(--blue-dark); font-weight: 800; cursor: pointer; }
.settings-grid { display: grid; grid-template-columns: repeat(3,1fr); gap: 10px; margin-top: 14px; }
.field.compact input, .field.compact select { font-size: .92rem; }
.fine-print { color: var(--muted); font-size: .77rem; line-height: 1.5; margin: 10px 0 0; }

.button-row { display: flex; gap: 10px; margin-top: 18px; }
.btn {
  border: 1px solid var(--line-strong);
  background: white;
  color: var(--ink);
  border-radius: 10px;
  padding: 10px 14px;
  font-weight: 800;
}
.btn:hover { border-color: var(--blue); color: var(--blue-dark); }
.btn.primary { background: var(--blue); border-color: var(--blue); color: white; }
.btn.primary:hover { background: var(--blue-dark); }
.btn.small { padding: 7px 10px; font-size: .78rem; }
.distance-actions { display: flex; gap: 8px; margin-top: 10px; }

.toggle-stack { display: grid; gap: 9px; margin-top: 18px; }
.toggle-row {
  display: grid;
  grid-template-columns: auto 1fr;
  column-gap: 12px;
  align-items: center;
  border: 1px solid var(--line);
  border-radius: 12px;
  padding: 11px 12px;
  background: #fbfdff;
  cursor: pointer;
  position: relative;
}
.toggle-row input { position: absolute; opacity: 0; pointer-events: none; }
.toggle-row > span:last-child { min-width: 0; }
.toggle-row strong { display: block; font-size: .88rem; }
.toggle-row small { display: block; color: var(--muted); font-size: .72rem; margin-top: 3px; line-height: 1.35; }
.switch {
  width: 42px;
  height: 24px;
  border-radius: 999px;
  background: #c7d2df;
  position: relative;
  transition: .18s ease;
}
.switch::after {
  content: "";
  position: absolute;
  width: 18px; height: 18px;
  border-radius: 50%;
  background: white;
  top: 3px; left: 3px;
  box-shadow: 0 1px 4px rgba(0,0,0,.22);
  transition: .18s ease;
}
.toggle-row input:checked + .switch { background: var(--blue); }
.toggle-row input:checked + .switch::after { transform: translateX(18px); }
.reflection-controls {
  margin-top: 12px;
  padding: 14px;
  border: 1px dashed var(--line-strong);
  border-radius: 12px;
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 14px;
}
.range-line { display: flex; align-items: center; gap: 10px; }
.range-line input[type="range"] { flex: 1; accent-color: var(--blue); }
.range-line output { font-family: var(--mono); font-size: .82rem; min-width: 46px; text-align: right; }
.loss-readout {
  margin-top: 12px;
  padding: 13px 14px;
  border-left: 4px solid var(--blue);
  background: var(--blue-soft);
  border-radius: 10px;
  display: grid;
  gap: 6px;
}
.loss-readout > div { display: flex; justify-content: space-between; gap: 16px; font-size: .78rem; }
.loss-readout span { color: var(--muted); }
.loss-readout strong { font-family: var(--mono); }

.visual-card { padding: 22px; margin-bottom: 18px; overflow: hidden; }
.visual-heading { display: grid; grid-template-columns: 1fr 290px; gap: 26px; align-items: end; }
.phase-field { max-width: 290px; }
.legend { display: flex; flex-wrap: wrap; gap: 16px; margin: 14px 0 8px; font-size: .78rem; color: var(--muted); }
.legend > span { display: inline-flex; align-items: center; gap: 7px; transition: opacity .15s; }
.legend > span.muted { opacity: .28; }
.legend-line { width: 26px; height: 0; border-top: 3px solid; display: inline-block; }
.legend-line.incident { border-color: var(--blue); }
.legend-line.reflected { border-color: var(--reflected); border-top-style: dashed; }
.legend-line.aggregate { border-color: var(--aggregate); border-top-width: 4px; }
.svg-wrap {
  position: relative;
  border: 1px solid var(--line-strong);
  border-radius: 14px;
  overflow: hidden;
  background: #fbfdff;
}
#waveSvg { display: block; width: 100%; height: auto; aspect-ratio: 1200 / 560; touch-action: none; }
.graph-bg { fill: #fbfdff; }
.grid-minor { stroke: #dce7f2; stroke-width: 1; }
.grid-major { stroke: #b9cee3; stroke-width: 1.25; }
.arrow-fill { fill: var(--blue); }
.arrow-dark-fill { fill: var(--ink); }
.dynamic-axis { stroke: #52667d; stroke-width: 1.5; }
.dynamic-zero { stroke: #73879e; stroke-width: 1.2; stroke-dasharray: 5 5; }
.dynamic-boundary { stroke: var(--ink); stroke-width: 2; stroke-dasharray: 7 7; }
.dynamic-incident { stroke: var(--blue); stroke-width: 3.2; fill: none; vector-effect: non-scaling-stroke; }
.dynamic-reflected { stroke: var(--reflected); stroke-width: 2.6; fill: none; stroke-dasharray: 9 6; vector-effect: non-scaling-stroke; }
.dynamic-aggregate { stroke: var(--aggregate); stroke-width: 4; fill: none; vector-effect: non-scaling-stroke; }
.dynamic-dimension { stroke: var(--blue); stroke-width: 1.8; fill: none; marker-start: url(#arrowBlue); marker-end: url(#arrowBlue); }
.dynamic-dimension-sub { stroke: var(--ink); stroke-width: 1.35; fill: none; marker-start: url(#arrowDark); marker-end: url(#arrowDark); }
.dynamic-tick { stroke: #52667d; stroke-width: 1.2; }
.dynamic-text { fill: #3f5369; font-family: var(--mono); font-size: 15px; }
.dynamic-text-strong { fill: var(--ink); font-family: var(--sans); font-size: 15px; font-weight: 800; }
.dynamic-text-blue { fill: var(--blue-dark); font-family: var(--mono); font-size: 15px; font-weight: 700; }
.dynamic-crosshair { stroke: #111827; stroke-width: 1.3; stroke-dasharray: 5 5; pointer-events: none; }
.dynamic-hover-dot { fill: #fff; stroke: var(--blue-dark); stroke-width: 2.5; pointer-events: none; }
.tooltip {
  position: absolute;
  min-width: 220px;
  max-width: 285px;
  padding: 10px 11px;
  border-radius: 10px;
  border: 1px solid #8ea4bb;
  background: rgba(12, 28, 48, .94);
  color: #fff;
  box-shadow: 0 10px 28px rgba(8, 24, 44, .25);
  pointer-events: none;
  font-size: .75rem;
  line-height: 1.48;
  z-index: 5;
}
.tooltip strong { color: #9fcbff; }
.tooltip .tt-grid { display: grid; grid-template-columns: auto 1fr; gap: 3px 12px; }
.tooltip .tt-grid span:nth-child(odd) { color: #b9c8d8; }
.tooltip .tt-grid span:nth-child(even) { font-family: var(--mono); text-align: right; }
.visual-footer { display: flex; justify-content: space-between; gap: 20px; color: var(--muted); font-size: .76rem; margin-top: 9px; }
#condensedWarning { color: var(--danger); font-weight: 750; }

.reference-grid { display: grid; grid-template-columns: .8fr 1.2fr; gap: 18px; margin-bottom: 18px; }
.formula-list { display: grid; gap: 8px; }
.formula-list > div { display: flex; justify-content: space-between; align-items: center; gap: 20px; border-bottom: 1px solid var(--line); padding: 9px 0; }
.formula-list span { color: var(--muted); font-size: .82rem; }
.formula-list strong { font-family: var(--mono); font-size: .95rem; }
.explainer-card p + p { margin-top: 14px; }
.assumption-columns { display: grid; grid-template-columns: repeat(3, 1fr); gap: 18px; }

.tool-footer {
  margin-top: 18px;
  padding: 20px 4px 6px;
  border-top: 3px solid var(--blue);
  display: flex;
  justify-content: space-between;
  align-items: flex-start;
  gap: 18px;
  color: var(--muted);
  font-size: .76rem;
}
.tool-footer strong { display: block; color: var(--ink); letter-spacing: .12em; }
.tool-footer span { display: block; margin-top: 3px; }
.footer-right { text-align: right; }

@media (max-width: 980px) {
  .calculator-grid, .reference-grid { grid-template-columns: 1fr; }
  .visual-heading { grid-template-columns: 1fr; }
  .phase-field { max-width: none; }
  .assumption-columns { grid-template-columns: 1fr; gap: 0; }
  .stats-grid { grid-template-columns: repeat(2, minmax(0,1fr)); }
}

@media (max-width: 720px) {
  .app-shell { width: min(100% - 18px, 1440px); padding-top: 12px; }
  .tool-header { padding: 14px 8px 20px; flex-direction: column; }
  .tool-logo { width: 58px; height: 58px; }
  .header-badges { justify-content: flex-start; }
  .intro-card { grid-template-columns: 1fr; padding: 18px; }
  .unit-controls { justify-content: flex-start; }
  .input-card, .distance-card, .reference-card, .explainer-card, .assumptions-card, .visual-card { padding: 17px; }
  .primary-inputs { grid-template-columns: 1fr; }
  .equals-mark { transform: rotate(90deg); text-align: center; padding: 0; }
  .settings-grid, .reflection-controls { grid-template-columns: 1fr; }
  .stats-grid, .stats-grid.two-col { grid-template-columns: 1fr 1fr; }
  #waveSvg { aspect-ratio: 900 / 560; }
  .visual-footer, .tool-footer { flex-direction: column; }
  .footer-right { text-align: left; }
}

@media (max-width: 480px) {
  .stats-grid, .stats-grid.two-col { grid-template-columns: 1fr; }
  .brand-lockup { align-items: flex-start; }
  .unit-controls { align-items: stretch; flex-direction: column; }
  .segmented { width: 100%; }
  .seg { flex: 1; }
}

[hidden] { display: none !important; }