: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;
  --ray-incident: #ad5a34;
  --ray-reflected: #245b49;
  --ray-refracted: #376e93;
  --ray-normal: #687069;
  font-family: ui-sans-serif, system-ui, -apple-system, BlinkMacSystemFont, "Segoe UI", "Noto Sans JP", "Hiragino Kaku Gothic ProN", Meiryo, sans-serif;
}

* { box-sizing: border-box; }
html { scroll-behavior: smooth; }
body { margin: 0; min-width: 0; color: var(--ink); background: var(--paper); line-height: 1.65; overflow-x: hidden; }
button, input { 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; }
p, dd, li, strong, span { overflow-wrap: anywhere; }

.assumption {
  max-width: 760px;
  margin: 15px 0 0;
  padding-left: 13px;
  border-left: 3px solid var(--accent);
  color: var(--muted);
  font-size: .9rem;
}

.tool-shell {
  display: grid;
  grid-template-columns: minmax(0, .9fr) minmax(0, 1.1fr);
  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); }

.section-heading { margin-bottom: 17px; }

.input-grid { display: grid; gap: 15px; }
.input-row { min-width: 0; }
.input-row > label { display: block; margin-bottom: 5px; font-weight: 720; }
.input-wrap {
  display: grid;
  grid-template-columns: minmax(0, 1fr) 94px;
  gap: 6px;
  align-items: stretch;
}
.input-wrap input,
.unit-label {
  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);
}
.input-wrap input:focus { border-color: var(--accent); }
.input-wrap input[aria-invalid="true"] {
  border-color: var(--danger);
  background: #fff8f8;
}
.unit-label {
  display: flex;
  align-items: center;
  color: var(--muted);
  font-size: .82rem;
  font-weight: 700;
}
.field-help {
  margin: 4px 0 0;
  color: var(--muted);
  font-size: .78rem;
}
.field-error {
  min-height: 1.25em;
  margin: 2px 0 0;
  color: var(--danger);
  font-size: .82rem;
}
.form-error {
  margin: 12px 0 0;
  padding: 8px 10px;
  border-left: 4px solid var(--danger);
  background: var(--danger-soft);
  color: #762525;
  font-size: .88rem;
}
.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); }
.button:disabled { cursor: not-allowed; opacity: .6; }

.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"],
.result-box[data-state="tir"] {
  border-color: var(--danger);
  background: var(--danger-soft);
}
.result-box[data-state="boundary"] {
  border-color: #4e7585;
  background: #e7f0f3;
}
.result-label {
  margin: 0;
  color: var(--accent);
  font-size: .8rem;
  font-weight: 780;
}
.result-box[data-state="error"] .result-label,
.result-box[data-state="tir"] .result-label { color: var(--danger); }
.result-box[data-state="boundary"] .result-label { color: #356276; }
.result-value {
  display: block;
  margin-top: 2px;
  font-size: clamp(1.45rem, 3.2vw, 2.05rem);
  line-height: 1.28;
  font-weight: 780;
  font-variant-numeric: tabular-nums;
}
.result-status {
  margin: 5px 0 0;
  color: #3f4c46;
  font-size: .9rem;
}
.result-details {
  display: grid;
  grid-template-columns: repeat(2, 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-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 .detail-wide { grid-column: 1 / -1; }
.result-details dt { color: var(--muted); font-size: .76rem; font-weight: 760; }
.result-details dd { margin: 2px 0 0; font-size: .84rem; font-weight: 650; }

.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);
}
.status-badge[data-state="boundary"] {
  border-color: #4e7585;
  background: #e7f0f3;
  color: #356276;
}
.status-badge[data-state="tir"],
.status-badge[data-state="error"] {
  border-color: var(--danger);
  background: var(--danger-soft);
  color: var(--danger);
}

.visual-metrics {
  display: grid;
  grid-template-columns: repeat(3, 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: 8px 9px;
  border-right: 1px solid var(--line);
  border-bottom: 1px solid var(--line);
}
.visual-metrics dt { color: var(--muted); font-size: .72rem; font-weight: 750; }
.visual-metrics dd {
  margin: 2px 0 0;
  font-size: .82rem;
  font-weight: 700;
  font-variant-numeric: tabular-nums;
}

.canvas-frame {
  margin-top: 15px;
  overflow: hidden;
  border: 1px solid var(--line-strong);
  background: var(--paper);
}
.canvas-frame canvas {
  display: block;
  width: 100%;
  height: auto;
  aspect-ratio: 16 / 9;
  background: var(--paper);
}
.canvas-description {
  min-height: 2.8em;
  margin: 11px 0 0;
  color: #38413b;
  font-size: .86rem;
}
.scale-note {
  margin: 7px 0 0;
  padding-left: 11px;
  border-left: 3px solid var(--line-strong);
  color: var(--muted);
  font-size: .76rem;
}
.diagram-legend {
  display: grid;
  grid-template-columns: repeat(2, minmax(0, 1fr));
  gap: 7px 12px;
  margin-top: 14px;
  color: var(--muted);
  font-size: .78rem;
}
.diagram-legend > span {
  display: flex;
  min-width: 0;
  align-items: center;
  gap: 7px;
}
.legend-swatch {
  display: inline-block;
  flex: 0 0 auto;
  width: 22px;
  height: 3px;
  background: var(--ray-normal);
}
.swatch-incident { background: var(--ray-incident); }
.swatch-reflected { background: var(--ray-reflected); }
.swatch-refracted { background: var(--ray-refracted); }
.swatch-normal {
  height: 0;
  border-top: 2px dashed var(--ray-normal);
  background: transparent;
}

.content-section {
  margin-top: 30px;
  padding-top: 25px;
  border-top: 1px solid var(--line-strong);
}
.steps-list {
  display: grid;
  grid-template-columns: repeat(4, 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);
  counter-increment: steps;
  font-size: .86rem;
}
.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 { font-size: .94rem; }
.formula-list span { color: var(--muted); font-size: .82rem; }
.meaning-panel {
  margin-top: 15px;
  padding: 16px;
  border: 1px solid var(--line);
  background: var(--surface);
}
.meaning-panel h3 {
  margin: 0;
  color: var(--accent);
  font-size: .98rem;
}
.meaning-panel p {
  margin: 7px 0 0;
  font-size: .88rem;
}
.meaning-panel ul {
  display: grid;
  grid-template-columns: repeat(2, minmax(0, 1fr));
  gap: 0 22px;
  margin: 10px 0 0;
  padding-left: 1.2em;
  color: var(--muted);
  font-size: .82rem;
}
.meaning-panel 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(2, minmax(0, 1fr)); }
  .steps-list li:nth-child(2) { border-right: 0; }
  .steps-list li:nth-child(-n + 2) { border-bottom: 1px solid var(--line); }
  .steps-list li:nth-child(3) { border-right: 1px solid var(--line); }
}

@media (max-width: 700px) {
  .formula-list { grid-template-columns: 1fr; }
  .meaning-panel ul { grid-template-columns: 1fr; }
  .calculator-panel,
  .visual-panel { padding: 18px; }
}

@media (max-width: 460px) {
  .input-wrap { grid-template-columns: minmax(0, 1fr) 82px; }
  .form-actions { display: grid; grid-template-columns: 1fr; }
  .button { width: 100%; }
  .result-details,
  .visual-metrics { grid-template-columns: repeat(2, minmax(0, 1fr)); }
  .result-details .detail-wide { grid-column: 1 / -1; }
  .steps-list { grid-template-columns: 1fr; }
  .steps-list li,
  .steps-list li:nth-child(2),
  .steps-list li:nth-child(3) {
    border-right: 0;
    border-bottom: 1px solid var(--line);
  }
  .steps-list li:last-child { border-bottom: 0; }
  .diagram-legend { gap: 6px; font-size: .74rem; }
}
@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;
  }
}