:root {
  color-scheme: light;
  --paper: #f4f2ec;
  --surface: #fbfaf6;
  --ink: #222824;
  --muted: #687069;
  --line: #cfd3cc;
  --line-strong: #9fa79f;
  --accent: #245b49;
  --accent-soft: #e2ebe5;
  --accent-strong: #173f32;
  --sky: #2d6880;
  --sky-soft: #dbeaf0;
  --danger: #9b2f2f;
  --danger-soft: #f8e9e7;
  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; color: var(--ink); background: var(--paper); line-height: 1.65; }
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; }

.tool-shell { display: grid; grid-template-columns: minmax(0, .98fr) minmax(0, 1.02fr); 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); }
.mode-fieldset, .values-fieldset { margin: 17px 0 0; padding: 0; border: 0; }
.mode-fieldset legend, .values-fieldset legend { margin-bottom: 8px; font-weight: 760; }
.values-fieldset { margin-top: 20px; }
.mode-options { display: grid; grid-template-columns: repeat(2, minmax(0, 1fr)); gap: 6px; }
.mode-option { position: relative; display: block; cursor: pointer; }
.mode-option input { position: absolute; opacity: 0; }
.mode-option span { min-height: 48px; display: grid; place-items: center; padding: 7px 8px; border: 1px solid var(--line); background: var(--surface); color: var(--muted); text-align: center; font-size: .87rem; font-weight: 700; line-height: 1.35; }
.mode-option input:checked + span { border-color: var(--accent); background: var(--accent-soft); color: var(--accent); }
.mode-option input:focus-visible + span { outline: 3px solid var(--accent); outline-offset: 2px; }
.input-grid { display: grid; gap: 14px; }
.input-row label { display: block; margin-bottom: 5px; font-weight: 720; }
.input-wrap { display: grid; grid-template-columns: minmax(0, 1fr) minmax(104px, .42fr); align-items: stretch; gap: 6px; }
.input-wrap input, .input-wrap select { 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[aria-invalid="true"] { border-color: var(--danger); background: #fff8f8; }
.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-actions { display: flex; 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); }
.form-error { margin: 12px 0 0; padding: 8px 10px; border-left: 4px solid var(--danger); background: var(--danger-soft); color: #762525; }
.form-error[hidden] { display: none; }

.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(1.45rem, 3.2vw, 2.05rem); 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-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: .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(2, 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: 318px; display: grid; place-items: center; margin-top: 15px; padding: 24px 12px 18px; overflow: hidden; border: 1px solid var(--line); background: linear-gradient(180deg, #f2f7f8 0%, #f8f4ec 100%); }
.atmosphere-figure { position: relative; width: min(100%, 405px); height: 270px; margin: 0; overflow: hidden; border: 1px solid var(--line-strong); background: linear-gradient(180deg, var(--sky-soft) 0%, #eef5f2 58%, #d9c7a8 58%, #d9c7a8 100%); }
.sky-band { position: absolute; inset: 0 0 42% 0; background: linear-gradient(180deg, rgba(255,255,255,.56), rgba(219,234,240,.2)); }
.sky-label { position: absolute; top: 12px; right: 16px; color: var(--sky); font-size: .76rem; font-weight: 760; }
.mountain { position: absolute; left: 10%; bottom: 42%; width: 72%; height: 56%; background: #5f806e; clip-path: polygon(0 100%, 37% 48%, 50% 64%, 71% 16%, 100% 100%); }
.mountain::after { content: ""; position: absolute; inset: 15% 28% auto 43%; height: 36%; background: #f9faf7; clip-path: polygon(50% 0, 100% 100%, 0 100%); opacity: .8; }
.sea-line { position: absolute; left: 0; right: 0; bottom: 42%; height: 3px; background: var(--sky); }
.sea-line span { position: absolute; left: 12px; top: -25px; color: var(--sky); font-size: .74rem; font-weight: 750; }
.pressure-column { position: absolute; top: 18%; right: 12%; width: 56px; height: 52%; border-left: 2px solid rgba(36,91,73,.6); }
.pressure-column::before, .pressure-column::after { content: ""; position: absolute; left: -7px; width: 12px; border-top: 2px solid var(--accent); }
.pressure-column::before { top: 0; } .pressure-column::after { bottom: 0; }
.pressure-brace { position: absolute; left: 13px; top: 0; bottom: 0; width: 16px; border-inline: 1px solid rgba(36,91,73,.55); }
.pressure-brace::before, .pressure-brace::after { content: ""; position: absolute; left: -1px; width: 16px; border-top: 1px solid rgba(36,91,73,.55); }
.pressure-brace::before { top: 50%; } .pressure-brace::after { bottom: 0; }
.pressure-mark { position: absolute; left: 33px; color: var(--accent); font-size: .74rem; font-weight: 760; }
.mark-top { top: -9px; } .mark-bottom { bottom: -9px; }
.altitude-chip, .pressure-chip { position: absolute; padding: 3px 8px; border: 1px solid var(--accent); background: rgba(251,250,246,.9); color: var(--accent); font-size: .78rem; font-weight: 780; }
.altitude-chip { left: 34%; bottom: 47%; } .pressure-chip { right: 7%; top: 38%; }
.visual-caption { position: absolute; inset: auto 10px 8px; color: #3c5347; font-size: .73rem; line-height: 1.35; text-align: center; }
.visual-description, .scale-note { margin: 12px 0 0; color: var(--muted); font-size: .84rem; }
.scale-note { margin-top: 6px; font-size: .76rem; }

.content-section { margin-top: 34px; }
.formula-list { display: grid; grid-template-columns: repeat(2, minmax(0, 1fr)); gap: 8px; margin-top: 15px; }
.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; }
.proof-guide { margin-top: 14px; padding: 16px; border: 1px solid var(--line); background: var(--surface); }
.proof-guide h3 { margin: 0; font-size: 1rem; }
.proof-guide ul { margin: 9px 0 0; padding-left: 1.2em; color: var(--muted); font-size: .84rem; }
.proof-guide li + li { margin-top: 5px; }

@media (max-width: 760px) {
  .tool-shell { grid-template-columns: 1fr; }
  .calculator-panel { border-right: 0; border-bottom: 1px solid var(--line); }
  .formula-list { grid-template-columns: 1fr; }
  .calculator-panel, .visual-panel { padding: 18px; }
}

@media (max-width: 460px) {
  .mode-options { grid-template-columns: 1fr; }
  .input-wrap { grid-template-columns: minmax(0, 1fr) 106px; }
  .form-actions { flex-wrap: wrap; }
  .form-actions .button { flex: 1 1 140px; }
  .result-details { grid-template-columns: 1fr; }
  .result-details .detail-wide { grid-column: auto; }
  .atmosphere-figure { height: 250px; }
}