:root {
  --paper: #f3ead8;
  --paper-2: #ebe0c9;
  --ink: #221d17;
  --ink-2: #5a5044;
  --rule: #cdbfa4;
  --ochre: #b9832a;
  --ochre-soft: #e3c48a;
  --teal: #1d6a66;
  --teal-soft: #b9d6cf;
  --rust: #9a4527;
  --steel: #6f6a62;
  --rubber: #3a3530;
  --serif: "Iowan Old Style", "Palatino Linotype", Palatino, "Book Antiqua", Georgia, serif;
  --sans: system-ui, -apple-system, "Segoe UI", Roboto, "Noto Sans", sans-serif;
  color-scheme: light;
}
:root { --rule: #cdbfa4; }

* { box-sizing: border-box; }
html { background: var(--paper); color: var(--ink); }
body {
  margin: 0 auto;
  max-width: 1240px;
  padding: 1.25rem clamp(1rem, 3vw, 2.5rem) 3rem;
  font: 17px/1.55 var(--serif);
}
h1, h2, h3, h4 { font-weight: 600; line-height: 1.15; margin: 0 0 .5rem; }
h1 { font-size: clamp(1.9rem, 4.5vw, 3.1rem); letter-spacing: -.01em; }
h1 span { display: block; font: 400 1rem/1.4 var(--sans); color: var(--ink-2); margin-top: .35rem; letter-spacing: .02em; }
h2 { font-size: 1.45rem; border-top: 1.5px solid var(--ink); padding-top: .6rem; margin-top: 2.4rem; }
h3 { font-size: 1.15rem; margin-top: 1.4rem; }
h4 { font: 600 .85rem/1.3 var(--sans); text-transform: uppercase; letter-spacing: .06em; color: var(--ink-2); }
a { color: var(--teal); text-underline-offset: 2px; }
button, input, select { font: inherit; }
:focus-visible { outline: 3px solid var(--teal); outline-offset: 2px; }

.visually-hidden {
  position: absolute !important; width: 1px; height: 1px; overflow: hidden;
  clip: rect(0 0 0 0); white-space: nowrap;
}
.skip { position: absolute; left: -9999px; }
.skip:focus { left: 1rem; top: 1rem; background: var(--ink); color: var(--paper); padding: .4rem .7rem; z-index: 10; }

.kicker { font: 600 .78rem/1 var(--sans); text-transform: uppercase; letter-spacing: .14em; color: var(--rust); margin: 0 0 .6rem; }
.lede { max-width: 44rem; color: var(--ink-2); font-size: 1.05rem; margin: .4rem 0 1rem; }
.hint { font: .9rem/1.45 var(--sans); color: var(--ink-2); max-width: 46rem; margin: 0 0 .8rem; }

.warning {
  border-left: 5px solid var(--rust);
  background: #f7e3d6;
  padding: .7rem 1rem;
  font: .95rem/1.45 var(--sans);
  margin: 0 0 1rem;
  position: sticky; top: 0; z-index: 5;
}
.warning strong { color: var(--rust); }

/* ---------- stage ---------- */
.stage { margin-top: .5rem; }
.figure { margin: 0; background: var(--paper-2); border: 1.5px solid var(--ink); }
.svg-host { width: 100%; }
.diagram { display: block; width: 100%; height: auto; max-height: 78vh; }
.caption { font: .88rem/1.4 var(--sans); padding: .5rem .8rem; border-top: 1px solid var(--rule); color: var(--ink-2); }
.fallback-note { padding: 1.5rem; font-family: var(--sans); }

.controls { display: grid; gap: .7rem; margin-top: .8rem; font-family: var(--sans); font-size: .95rem; }
.transport { display: flex; gap: .4rem; flex-wrap: wrap; }
.controls button, .note-actions button {
  border: 1.5px solid var(--ink); background: var(--paper); color: var(--ink);
  padding: .45rem .9rem; min-height: 44px; min-width: 44px; cursor: pointer; border-radius: 2px;
}
.controls button:hover:not(:disabled) { background: var(--ochre-soft); }
#btn-play { background: var(--ink); color: var(--paper); min-width: 6.5rem; }
#btn-play[aria-pressed="true"] { background: var(--teal); border-color: var(--teal); }
button:disabled { opacity: .45; cursor: not-allowed; }
.scrub input { width: 100%; accent-color: var(--ochre); min-height: 32px; }
.frames { list-style: none; margin: 0; padding: 0; display: grid; grid-template-columns: repeat(5, 1fr); gap: .3rem; }
.frames button { width: 100%; text-align: left; font-size: .85rem; line-height: 1.2; padding: .4rem .5rem; }
.frames button[aria-current="step"] { background: var(--ochre); border-color: var(--ochre); color: var(--ink); }
.frame-n { font-weight: 700; margin-right: .2rem; }
.modes { display: flex; flex-wrap: wrap; gap: .7rem; }
.seg { border: 1px solid var(--rule); padding: .35rem .7rem .5rem; margin: 0; display: flex; flex-wrap: wrap; gap: .3rem 1rem; }
.seg legend { font-size: .75rem; text-transform: uppercase; letter-spacing: .08em; color: var(--ink-2); padding: 0 .3rem; }
.seg label { display: inline-flex; align-items: center; gap: .35rem; min-height: 36px; cursor: pointer; }
.seg input { accent-color: var(--teal); width: 1.1rem; height: 1.1rem; }

/* ---------- SVG parts ---------- */
.diagram .body { fill: none; stroke: var(--ink-2); stroke-width: 3; }
.diagram .ctx-label { font: italic 11px var(--serif); fill: var(--ink-2); }
.diagram .road { fill: #d9c9a8; stroke: var(--ink); stroke-width: 1.5; }
.diagram .road-ref { stroke: var(--ink-2); stroke-dasharray: 3 5; stroke-width: 1; }
.diagram .hatch-line { stroke: var(--ink-2); stroke-width: 1; }
.part { cursor: pointer; transition: transform .6s cubic-bezier(.2,.7,.2,1), opacity .25s; outline: none; }
.part .hit { stroke: transparent; stroke-width: 18; fill: none; stroke-linecap: round; }
.part:focus-visible { filter: drop-shadow(0 0 0 var(--teal)) drop-shadow(0 0 3px var(--teal)); }
.part:hover { filter: drop-shadow(0 0 2px var(--ochre)); }
.part.is-dim { opacity: .13; }
.part.is-selected * { stroke: var(--teal); }
.part.is-selected .tyre { stroke: #2b5e5a; }

.tyre { fill: none; stroke: #2f2a25; stroke-width: 18; }
.rim { fill: #e7dcc4; stroke: var(--steel); stroke-width: 3; }
.spokes line { stroke: var(--steel); stroke-width: 7; stroke-linecap: round; }
.valve { fill: var(--ochre); }
.shaft { stroke: #8a8278; stroke-width: 9; stroke-linecap: round; }
.boot { fill: var(--rubber); stroke: var(--ink); stroke-width: 1; }
.frame { fill: url(#hatch); stroke: var(--ink); stroke-width: 2; }
.rubber { fill: var(--rubber); stroke: var(--ink); stroke-width: 1; }
.rubber.ring { fill: var(--rubber); stroke: #8a8278; stroke-width: 4; }
.disc { fill: #b9b2a6; stroke: var(--ink-2); stroke-width: 2; }
.disc-hat { fill: #9c958a; stroke: var(--ink-2); stroke-width: 1.5; }
.caliper { fill: var(--rust); stroke: var(--ink); stroke-width: 1.5; }
.knuckle { fill: #8f877b; stroke: var(--ink); stroke-width: 2; stroke-linejoin: round; }
.hub { fill: #d8cfbd; stroke: var(--ink); stroke-width: 2; }
.bar { fill: none; stroke: var(--teal); stroke-width: 8; stroke-linecap: round; }
.arm { stroke: #57514a; stroke-width: 15; stroke-linecap: round; }
.joint { fill: var(--ochre); stroke: var(--ink); stroke-width: 2; }
.rack { fill: #9c958a; stroke: var(--ink); stroke-width: 1.5; }
.tierod { stroke: #6f6a62; stroke-width: 6; stroke-linecap: round; }
.rod { stroke: #c9c3b8; stroke-width: 7; stroke-linecap: round; }
.tube { stroke: var(--ink); stroke-width: 22; stroke-linecap: butt; }
.lower-seat { stroke: var(--ink); stroke-width: 5; stroke-linecap: round; }
.bellows { fill: #4a443d; stroke: var(--ink); stroke-width: 1; }
.coil { fill: none; stroke: var(--ochre); stroke-width: 7; stroke-linejoin: round; stroke-linecap: round; }
.upper-seat { stroke: var(--rubber); stroke-width: 9; stroke-linecap: round; }
.mount-plate { stroke: #57514a; stroke-width: 11; stroke-linecap: round; }
.bearing { fill: var(--ochre-soft); stroke: var(--ink); stroke-width: 2; }
.link { stroke: var(--teal); stroke-width: 6; stroke-linecap: round; }
.part.is-selected .coil, .part.is-selected .bar, .part.is-selected .link { stroke: var(--rust); }
.callout line { stroke: var(--ink); stroke-width: 1; }
.callout circle { fill: var(--ink); }
.callout text { font: 600 13px var(--sans); fill: var(--ink); paint-order: stroke; stroke: var(--paper-2); stroke-width: 5px; stroke-linejoin: round; }

/* ---------- parts & card ---------- */
.parts-grid { display: grid; grid-template-columns: minmax(0, 1fr) minmax(0, 1.25fr); gap: 1.5rem; align-items: start; }
.parts-list { list-style: none; margin: 0; padding: 0; columns: 1; font-family: var(--sans); }
.part-btn {
  width: 100%; text-align: left; background: none; border: 0; border-bottom: 1px solid var(--rule);
  padding: .5rem .3rem; min-height: 44px; cursor: pointer; color: var(--ink); font-size: .95rem;
}
.part-btn:hover { background: var(--paper-2); }
.part-btn.is-on { background: var(--teal-soft); }
.tier { display: inline-block; width: 1.6em; text-align: center; font: 700 .8rem/1.6 var(--sans); border: 1.5px solid currentColor; margin-right: .3rem; }
.tier-A.tier, .tier-col.tier-A h4 { color: var(--rust); }
.tier-B.tier, .tier-col.tier-B h4 { color: var(--ochre); }
.tier-C.tier, .tier-col.tier-C h4 { color: var(--teal); }
.card { border: 1.5px solid var(--ink); background: #fbf6ec; padding: 1rem 1.2rem; position: sticky; top: 4.5rem; }
.card-empty { color: var(--ink-2); font-style: italic; margin: 0; }
.card h3 { margin-top: .3rem; font-size: 1.4rem; }
.card-en { font: .85rem var(--sans); color: var(--ink-2); margin: 0 0 .8rem; }
.card-tier { font: .8rem var(--sans); color: var(--ink-2); margin: 0; }
.card dl { display: grid; grid-template-columns: max-content 1fr; gap: .35rem 1rem; margin: 0 0 1rem; }
.card dt { font: 600 .78rem/1.6 var(--sans); text-transform: uppercase; letter-spacing: .05em; color: var(--ink-2); }
.card dd { margin: 0; }
.card-sources { font: .85rem/1.5 var(--sans); padding-left: 1rem; margin: 0; }

/* ---------- symptoms ---------- */
.symptom-table { overflow-x: auto; }
table { border-collapse: collapse; width: 100%; font: .92rem/1.4 var(--sans); }
th, td { text-align: left; vertical-align: top; padding: .55rem .5rem; border-bottom: 1px solid var(--rule); }
thead th { font-size: .75rem; text-transform: uppercase; letter-spacing: .06em; color: var(--ink-2); border-bottom: 1.5px solid var(--ink); }
.chip {
  display: inline-block; margin: 0 .3rem .3rem 0; padding: .3rem .6rem; min-height: 36px;
  border: 1px solid var(--rule); background: var(--paper); border-left: 4px solid currentColor;
  cursor: pointer; font: .88rem var(--sans); color: var(--ink); text-align: left;
}
.chip.tier-A { border-left-color: var(--rust); }
.chip.tier-B { border-left-color: var(--ochre); }
.chip.tier-C { border-left-color: var(--teal); }
.chip.is-on { background: var(--teal-soft); }
.tiers { display: grid; grid-template-columns: repeat(3, minmax(0, 1fr)); gap: 1rem; }
.tier-col ol { margin: 0; padding-left: 1.3rem; }

/* ---------- safety ---------- */
.safety-form { display: grid; gap: .6rem; font-family: var(--sans); }
.q { border: 1px solid var(--rule); padding: .6rem .9rem; margin: 0; display: flex; flex-wrap: wrap; gap: .4rem 1.2rem; }
.q legend { padding: 0 .3rem; font-size: .98rem; max-width: 60rem; }
.q-n { font-weight: 700; color: var(--rust); }
.q label { display: inline-flex; gap: .35rem; align-items: center; min-height: 40px; cursor: pointer; }
.q input { accent-color: var(--rust); width: 1.15rem; height: 1.15rem; }
.safety-result { font: 600 1rem/1.45 var(--sans); padding: .8rem 1rem; border-left: 5px solid var(--ochre); background: var(--paper-2); }
.safety-result[data-level="stop"], .stop-banner { border-left: 5px solid var(--rust); background: #f2d2c3; color: #5c1e0b; }
.safety-result[data-level="inspect"] { border-left-color: var(--teal); }
.stop-banner { font: 600 1rem var(--sans); padding: .7rem 1rem; }

/* ---------- note ---------- */
.obs-form { display: grid; grid-template-columns: repeat(auto-fill, minmax(14rem, 1fr)); gap: .6rem 1rem; font: .9rem var(--sans); margin-bottom: 1rem; }
.obs { display: grid; gap: .2rem; }
.obs select { padding: .4rem; min-height: 40px; border: 1px solid var(--ink-2); background: #fbf6ec; color: var(--ink); }
.roads { border: 1px solid var(--rule); margin: 0; display: flex; flex-wrap: wrap; gap: .3rem .9rem; grid-column: 1 / -1; }
.roads label { display: inline-flex; gap: .3rem; align-items: center; min-height: 36px; }
.summary {
  white-space: pre-wrap; background: #fbf6ec; border: 1.5px dashed var(--ink-2); padding: 1rem;
  font: .88rem/1.5 ui-monospace, "SFMono-Regular", Menlo, Consolas, monospace; max-width: 48rem;
}
.note-actions { display: flex; gap: .5rem; align-items: center; flex-wrap: wrap; font-family: var(--sans); }

/* ---------- sources ---------- */
.sources-list { font: .88rem/1.5 var(--sans); padding-left: 0; list-style: none; columns: 2 26rem; column-gap: 2rem; }
.sources-list li { break-inside: avoid; margin-bottom: .45rem; }
.sources-list li:target { background: var(--ochre-soft); }
.src-id { font-weight: 700; color: var(--ink-2); }
.src-note { color: var(--ink-2); }
.colophon { margin-top: 3rem; border-top: 1px solid var(--rule); font: .82rem var(--sans); color: var(--ink-2); }

/* ---------- responsive ---------- */
@media (max-width: 820px) {
  body { font-size: 16px; }
  .parts-grid { grid-template-columns: 1fr; }
  .card { position: static; }
  .tiers { grid-template-columns: 1fr; }
  .frames { grid-template-columns: repeat(5, minmax(0, 1fr)); }
  .frames button { font-size: .72rem; padding: .35rem .3rem; }
  .warning { position: static; }
  .diagram { max-height: none; }
}
@media (max-width: 480px) {
  .frames button .frame-n { display: block; }
  .card dl { grid-template-columns: 1fr; }
}

/* ---------- reduced motion ---------- */
@media (prefers-reduced-motion: reduce) {
  *, *::before, *::after { transition: none !important; animation: none !important; scroll-behavior: auto !important; }
}
html.still .part { transition: none; }

@media print {
  .controls, .note-actions, .obs-form, .safety-form { display: none; }
  .warning { position: static; }
}