:root {
  color-scheme: light;
  --paper: #f5f4ef;
  --surface: #fbfaf6;
  --ink: #222824;
  --muted: #687069;
  --line: #cfd3cc;
  --line-strong: #9fa79f;
  --accent: #245b49;
  --accent-soft: #e2ebe5;
  --accent-strong: #173f32;
  --danger: #9b2f2f;
  --danger-soft: #f8e9e7;
  --hot: #b85c3e;
  --hot-soft: #f3d8ca;
  --cold: #3f7181;
  --cold-soft: #dbecef;
  --plate: #918979;
  font-family: ui-sans-serif, system-ui, -apple-system, BlinkMacSystemFont, "Segoe UI", "Noto Sans JP", "Hiragino Kaku Gothic ProN", Meiryo, sans-serif;
}

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

html { scroll-behavior: smooth; }
body { margin: 0; color: var(--ink); background: var(--paper); line-height: 1.65; overflow-x: hidden; }
button, input, select { font: inherit; }
a { color: inherit; }
:focus-visible { outline: 3px solid var(--accent); outline-offset: 3px; }

.eyebrow,
.section-kicker {
  margin: 0 0 5px;
  color: var(--accent);
  font-size: .78rem;
  font-weight: 780;
  letter-spacing: .08em;
  text-transform: uppercase;
}

h2 { margin: 0; font-size: clamp(1.2rem, 2vw, 1.48rem); line-height: 1.35; }
h3 { margin: 0; font-size: 1rem; }

.assumption {
  max-width: 730px;
  margin: 11px 0 0;
  padding-left: 12px;
  border-left: 3px solid var(--line-strong);
  color: var(--muted);
  font-size: .82rem;
  line-height: 1.6;
  overflow-wrap: anywhere;
}

.tool-shell {
  display: grid;
  grid-template-columns: minmax(0, .96fr) minmax(0, 1.04fr);
  border: 1px solid var(--line-strong);
  background: var(--surface);
}

.calculator-panel,
.visual-panel { min-width: 0; padding: 24px; }
.calculator-panel { border-right: 1px solid var(--line); }

.values-fieldset { margin: 17px 0 0; padding: 0; border: 0; }
.values-fieldset legend { margin-bottom: 9px; font-weight: 760; }
.input-grid { display: grid; gap: 14px; }
.input-row { min-width: 0; }
.input-row label { display: block; margin-bottom: 5px; font-weight: 720; }

.unit-field {
  display: grid;
  grid-template-columns: minmax(0, 1fr) auto;
  align-items: stretch;
  gap: 6px;
  min-width: 0;
}
.unit-field input {
  width: 100%;
  min-width: 0;
  min-height: 44px;
  border: 1px solid var(--line-strong);
  border-radius: 2px;
  padding: 9px 10px;
  color: var(--ink);
  background: var(--surface);
  font-variant-numeric: tabular-nums;
}
.unit-field input:focus { border-color: var(--accent); }
.unit-field input[aria-invalid="true"] { border-color: var(--danger); background: #fff8f8; }
.unit-label {
  display: grid;
  min-width: 96px;
  min-height: 44px;
  place-items: center;
  padding: 7px 10px;
  border: 1px solid var(--line-strong);
  background: #f0efe9;
  color: var(--muted);
  font-size: .82rem;
  font-weight: 700;
  line-height: 1.25;
  text-align: center;
  white-space: nowrap;
}
.field-help { margin: 4px 0 0; color: var(--muted); font-size: .78rem; overflow-wrap: anywhere; }
.field-error { min-height: 1.25em; margin: 2px 0 0; color: var(--danger); font-size: .82rem; overflow-wrap: anywhere; }
.form-error { margin: 12px 0 0; padding: 8px 10px; border-left: 4px solid var(--danger); background: var(--danger-soft); color: #762525; overflow-wrap: anywhere; }
.form-error[hidden] { display: none; }

.form-actions { display: flex; flex-wrap: wrap; gap: 8px; margin-top: 17px; }
.button { min-height: 42px; border: 1px solid var(--accent); border-radius: 2px; padding: 8px 15px; cursor: pointer; font-weight: 760; }
.button-primary { background: var(--accent); color: #fff; }
.button-primary:hover { background: var(--accent-strong); }
.button-secondary { background: var(--surface); color: var(--accent); }
.button:hover:not(:disabled) { border-color: var(--ink); }

.result-box {
  margin-top: 20px;
  padding: 15px 16px;
  border: 1px solid var(--accent);
  border-left-width: 4px;
  background: var(--accent-soft);
}
.result-box[data-state="error"] { border-color: var(--danger); background: var(--danger-soft); }
.result-label { margin: 0; color: var(--accent); font-size: .8rem; font-weight: 780; }
.result-box[data-state="error"] .result-label { color: var(--danger); }
.result-value { display: block; margin-top: 2px; font-size: clamp(1.25rem, 3vw, 1.85rem); line-height: 1.28; font-weight: 780; font-variant-numeric: tabular-nums; overflow-wrap: anywhere; }
.result-status { margin: 5px 0 0; color: #3f4c46; font-size: .9rem; overflow-wrap: anywhere; }

.result-metrics {
  display: grid;
  grid-template-columns: repeat(3, minmax(0, 1fr));
  margin: 14px 0 0;
  border-top: 1px solid rgba(36, 91, 73, .35);
  border-left: 1px solid rgba(36, 91, 73, .35);
}
.result-metrics[hidden] { display: none; }
.result-metrics div { min-width: 0; padding: 9px 10px; border-right: 1px solid rgba(36, 91, 73, .35); border-bottom: 1px solid rgba(36, 91, 73, .35); }
.result-metrics dt { color: var(--muted); font-size: .75rem; font-weight: 760; }
.result-metrics dd { margin: 2px 0 0; color: var(--accent); font-size: .9rem; font-weight: 780; overflow-wrap: anywhere; }

.result-details { display: grid; grid-template-columns: 1fr; margin: 14px 0 0; border-top: 1px solid rgba(36, 91, 73, .35); border-left: 1px solid rgba(36, 91, 73, .35); }
.result-details[hidden] { display: none; }
.result-details div { min-width: 0; padding: 9px 10px; border-right: 1px solid rgba(36, 91, 73, .35); border-bottom: 1px solid rgba(36, 91, 73, .35); }
.result-details dt { color: var(--muted); font-size: .76rem; font-weight: 760; }
.result-details dd { margin: 2px 0 0; font-size: .86rem; font-weight: 650; overflow-wrap: anywhere; }

.visual-heading-row { display: flex; justify-content: space-between; align-items: flex-start; gap: 14px; }
.status-badge { flex: 0 0 auto; padding: 3px 8px; border: 1px solid var(--line-strong); background: var(--paper); color: var(--muted); font-size: .75rem; font-weight: 760; }
.status-badge[data-state="ready"] { border-color: var(--accent); background: var(--accent-soft); color: var(--accent); }
.visual-metrics { display: grid; grid-template-columns: repeat(4, minmax(0, 1fr)); margin: 15px 0 0; border-top: 1px solid var(--line); border-left: 1px solid var(--line); }
.visual-metrics div { min-width: 0; padding: 9px 10px; border-right: 1px solid var(--line); border-bottom: 1px solid var(--line); }
.visual-metrics dt { color: var(--muted); font-size: .75rem; font-weight: 750; }
.visual-metrics dd { margin: 2px 0 0; font-size: .85rem; font-weight: 700; overflow-wrap: anywhere; }

.visual-stage {
  min-height: 345px;
  display: grid;
  place-items: center;
  margin-top: 15px;
  padding: 24px 12px 18px;
  overflow: hidden;
  border: 1px solid var(--line);
  background: linear-gradient(180deg, #f8f3ee 0%, #f3f5f1 100%);
}
.plate-figure {
  position: relative;
  width: min(100%, 440px);
  height: 300px;
  margin: 0;
  overflow: hidden;
  border: 1px solid var(--line-strong);
  background: linear-gradient(180deg, #fbf8f1 0%, #f5f1e8 100%);
}
.temperature-block {
  position: absolute;
  top: 95px;
  z-index: 1;
  display: grid;
  width: 23%;
  height: 90px;
  place-items: center;
  padding: 8px;
  color: #fff;
  font-size: .82rem;
  font-weight: 780;
  text-align: center;
  text-shadow: 0 1px 2px rgba(0, 0, 0, .35);
}
.block-hot { left: 7%; border: 1px solid #934832; background: linear-gradient(135deg, #a84932, #dc8e52); }
.block-cold { right: 7%; border: 1px solid #315d6c; background: linear-gradient(135deg, #5b91a0, #315f72); }
.plate-slab {
  position: absolute;
  top: 88px;
  left: 30%;
  z-index: 2;
  width: 40%;
  height: 104px;
  display: grid;
  place-items: center;
  border: 2px solid #716a5d;
  background: linear-gradient(90deg, #b4aa97 0%, #ddd3c0 48%, #9e9483 100%);
  box-shadow: 0 3px 0 rgba(34, 40, 36, .12);
}
.plate-slab::after { content: ""; position: absolute; inset: 0; background: repeating-linear-gradient(100deg, rgba(255, 255, 255, .22) 0 2px, transparent 2px 12px); pointer-events: none; }
.plate-label { position: relative; z-index: 1; padding: 4px 7px; background: rgba(251, 250, 246, .88); color: #4d493f; font-size: .8rem; font-weight: 780; text-align: center; }
.heat-arrow { position: absolute; top: 48px; left: 20%; right: 20%; z-index: 3; color: var(--accent); text-align: center; font-size: .92rem; font-weight: 800; }
.heat-arrow::before { content: ""; position: absolute; top: 50%; left: 0; right: 0; border-top: 2px solid var(--accent); z-index: 0; }
.heat-arrow span { position: relative; z-index: 1; padding: 0 8px; background: #fbf8f1; }
.temperature-gradient { position: absolute; right: 14%; bottom: 57px; left: 14%; display: flex; align-items: center; gap: 7px; color: var(--muted); font-size: .72rem; font-weight: 760; }
.temperature-gradient > span:not(.gradient-track) { flex: 0 0 auto; }
.gradient-track { height: 10px; flex: 1 1 auto; border: 1px solid var(--line-strong); background: linear-gradient(90deg, #c15b3d 0%, #e1b06a 46%, #5c94a3 100%); }
.visual-caption { position: absolute; inset: auto 10px 10px; color: #3c5347; font-size: .73rem; line-height: 1.35; text-align: center; }
.visual-description { margin: 12px 0 0; color: var(--muted); font-size: .84rem; overflow-wrap: anywhere; }
.scale-note { margin: 6px 0 0; padding-left: 11px; border-left: 3px solid var(--line-strong); color: var(--muted); font-size: .76rem; overflow-wrap: anywhere; }

.content-section { margin-top: 34px; padding-top: 25px; border-top: 1px solid var(--line-strong); }
.section-heading { margin-bottom: 15px; }
.steps-list { display: grid; grid-template-columns: repeat(5, minmax(0, 1fr)); gap: 0; margin: 0; padding: 0; border-block: 1px solid var(--line); list-style: none; counter-reset: steps; }
.steps-list li { position: relative; min-width: 0; padding: 35px 12px 13px; border-right: 1px solid var(--line); background: transparent; counter-increment: steps; font-size: .86rem; overflow-wrap: anywhere; }
.steps-list li:last-child { border-right: 0; }
.steps-list li::before { content: counter(steps, decimal-leading-zero); position: absolute; top: 7px; left: 12px; color: var(--accent); font-size: .75rem; font-weight: 800; }
.formula-list { display: grid; grid-template-columns: repeat(3, minmax(0, 1fr)); gap: 8px; }
.formula-list article { display: grid; gap: 4px; min-width: 0; padding: 14px; border: 1px solid var(--line); background: var(--surface); }
.formula-list strong { overflow-wrap: anywhere; font-size: .95rem; }
.formula-list span { color: var(--muted); font-size: .82rem; overflow-wrap: anywhere; }
.example-box { margin-top: 14px; padding: 14px 16px; border: 1px solid var(--accent); background: var(--accent-soft); }
.example-box h3 { color: var(--accent); font-size: .95rem; }
.example-box p { margin: 7px 0 0; color: #38413b; font-size: .88rem; overflow-wrap: anywhere; }
.proof-guide { margin-top: 14px; padding: 16px; border: 1px solid var(--line); background: var(--surface); }
.proof-guide ul { display: grid; grid-template-columns: repeat(2, minmax(0, 1fr)); gap: 0 22px; margin: 9px 0 0; padding-left: 1.2em; color: var(--muted); font-size: .84rem; }
.proof-guide li { overflow-wrap: anywhere; }
.proof-guide li + li { margin-top: 5px; }

@media (max-width: 900px) {
  .tool-shell { grid-template-columns: 1fr; }
  .calculator-panel { border-right: 0; border-bottom: 1px solid var(--line); }
  .steps-list { grid-template-columns: repeat(3, minmax(0, 1fr)); }
  .steps-list li:nth-child(3) { border-right: 0; }
  .steps-list li:nth-child(-n + 3) { border-bottom: 1px solid var(--line); }
}

@media (max-width: 760px) {
  .formula-list { grid-template-columns: 1fr; }
  .calculator-panel, .visual-panel { padding: 18px; }
  .proof-guide ul { grid-template-columns: 1fr; }
}

@media (max-width: 560px) {
  .result-metrics { grid-template-columns: 1fr; }
  .visual-metrics { grid-template-columns: repeat(2, minmax(0, 1fr)); }
  .plate-figure { height: 275px; }
  .temperature-block { top: 87px; height: 80px; }
  .plate-slab { top: 80px; height: 94px; }
  .heat-arrow { top: 39px; }
  .temperature-gradient { bottom: 52px; }
  .steps-list { grid-template-columns: 1fr; }
  .steps-list li,
  .steps-list li:nth-child(3) { border-right: 0; border-bottom: 1px solid var(--line); }
  .steps-list li:last-child { border-bottom: 0; }
}

@media (max-width: 390px) {
  .unit-label { min-width: 90px; padding-inline: 7px; font-size: .76rem; }
  .plate-figure { height: 260px; }
  .temperature-block { width: 25%; }
  .block-hot { left: 5%; }
  .block-cold { right: 5%; }
  .plate-slab { left: 30%; width: 40%; }
  .temperature-gradient { right: 8%; left: 8%; }
}

@media (prefers-reduced-motion: reduce) {
  html { scroll-behavior: auto; }
  *, *::before, *::after { scroll-behavior: auto !important; transition-duration: .01ms !important; animation-duration: .01ms !important; animation-iteration-count: 1 !important; }
}