:root {
  --ink: #1c2430;
  --muted: #4a5563;
  --paper: #ffffff;
  --bg: #eef2f5;
  --line: #c5d0d8;
  --air: #15608a;
  --air-soft: #d6ebf5;
  --ref: #b4531a;
  --ref-soft: #f6e3d4;
  --outdoor: #0b8ea3;
  --warm: #c0392b;
  --accent: #0b5f4a;
  --accent-soft: #d7efe7;
  --warn: #7a3e12;
  --focus: #0b5f4a;
  --box: #8b6914;
  --room: #f8fbfc;
  --shadow: 0 1px 2px rgba(28, 36, 48, 0.08);
}

* { box-sizing: border-box; }

html, body {
  margin: 0;
  padding: 0;
  background: var(--bg);
  color: var(--ink);
  font: 16px/1.45 "Segoe UI", "Helvetica Neue", Arial, sans-serif;
  overflow-x: hidden;
  max-width: 100%;
}

.skip {
  position: absolute;
  left: 0.75rem;
  top: -3rem;
  background: var(--paper);
  color: var(--ink);
  padding: 0.4rem 0.7rem;
  z-index: 5;
}

.skip:focus,
.skip:focus-visible { top: 0.5rem; }

.studio-return {
  margin: 0;
  padding: 0.65rem 1.5rem 0;
  background: var(--paper);
  border-bottom: 1px solid var(--line);
}

.studio-return a {
  color: var(--accent);
  font-weight: 650;
  text-decoration: underline;
}

.publication-lead {
  margin: 0.45rem 0 0;
  max-width: 46rem;
  color: var(--ink);
}

.top {
  display: flex;
  justify-content: space-between;
  gap: 1rem;
  align-items: flex-start;
  padding: 1.2rem 1.5rem 0.75rem;
  background: var(--paper);
  border-bottom: 1px solid var(--line);
}

.eyebrow {
  margin: 0;
  color: var(--muted);
  font-size: 0.8rem;
}

h1 {
  margin: 0.15rem 0 0;
  font-size: 1.35rem;
  font-weight: 650;
}

.lesson {
  margin: 0.2rem 0 0;
  color: var(--muted);
}

.toolbar {
  display: flex;
  flex-wrap: wrap;
  gap: 0.6rem;
  align-items: center;
  justify-content: flex-end;
}

.lang {
  display: flex;
  border: 1px solid var(--line);
  border-radius: 8px;
  overflow: hidden;
}

.lang button {
  appearance: none;
  border: 0;
  background: var(--paper);
  color: var(--ink);
  padding: 0.4rem 0.7rem;
  min-height: 2.25rem;
  font: inherit;
  cursor: pointer;
}

.lang button + button { border-inline-start: 1px solid var(--line); }

.lang button[aria-pressed="true"] {
  background: var(--accent);
  color: #fff;
  font-weight: 650;
}

.elapsed {
  margin: 0;
  color: var(--muted);
  font-size: 0.85rem;
}

.scenario-bar {
  display: grid;
  grid-template-columns: repeat(3, minmax(0, 1fr));
  gap: 0.6rem;
  padding: 0.75rem 1.5rem 0;
  max-width: 1500px;
  margin: 0 auto;
}

.scenario-card {
  appearance: none;
  font: inherit;
  text-align: start;
  cursor: pointer;
  border: 2px solid var(--line);
  background: var(--paper);
  border-radius: 10px;
  padding: 0.65rem 0.75rem;
  min-height: 4.4rem;
  color: var(--ink);
  box-shadow: var(--shadow);
}

.scenario-card[aria-pressed="true"] {
  border-style: solid;
  border-width: 3px;
  border-color: var(--ink);
  background: #f3faf7;
  box-shadow: inset 4px 0 0 var(--accent);
}

[dir="rtl"] .scenario-card[aria-pressed="true"] {
  box-shadow: inset -4px 0 0 var(--accent);
}

.scenario-card .sc-title {
  display: block;
  font-weight: 650;
}

.scenario-card .sc-short {
  display: block;
  color: var(--muted);
  font-size: 0.86rem;
  margin: 0.15rem 0;
}

.scenario-card .sc-status {
  display: inline-block;
  font-size: 0.75rem;
  font-weight: 650;
  letter-spacing: 0.01em;
  border: 1px solid var(--line);
  border-radius: 999px;
  padding: 0.05rem 0.45rem;
  background: #f6f8fa;
}

.scenario-card[data-status="active"] .sc-status {
  border-style: dashed;
  border-color: var(--ink);
}

.scenario-card[data-status="done"] .sc-status::before {
  content: "✓ ";
}

.layout {
  display: grid;
  grid-template-columns: minmax(0, 1.2fr) minmax(320px, 1fr);
  gap: 1.3rem;
  padding: 1rem 1.5rem 2rem;
  max-width: 1500px;
  margin: auto;
  align-items: start;
}

.layout > * { min-width: 0; }

.diagram-panel,
.task-panel {
  background: var(--paper);
  border: 1px solid var(--line);
  border-radius: 12px;
  box-shadow: var(--shadow);
}

.diagram-panel { margin: 0; padding: 1rem; }

.diagram-frame {
  direction: ltr;
  unicode-bidi: isolate;
  background: #fff;
  border: 1px solid var(--line);
  border-radius: 10px;
  max-width: 100%;
  min-width: 0;
  overflow: auto;
}

#plant-svg {
  display: block;
  width: 100%;
  height: auto;
  min-width: 0;
}

.diagram-frame.is-zoomed #plant-svg { min-width: 820px; }

.diagram-zoom { margin-block-start: 0.8rem; }

.grille {
  fill: #cfe0e8;
  stroke: var(--ink);
  stroke-width: 1;
}

#boxes-group { visibility: hidden; }
body[data-scenario="boxes"].show-defect #boxes-group,
body[data-scenario="boxes"].path-clear #boxes-group { visibility: visible; }
body[data-scenario="boxes"].path-clear #boxes-group { transform: translate(-210px, 42px); }

.air-arrow {
  fill: none;
  stroke: var(--air);
  stroke-width: 3;
  stroke-linecap: round;
  stroke-dasharray: 8 8;
}

#air-loop.air-weak .air-arrow { stroke-width: 2.5; opacity: 0.5; }
#air-loop.air-strong .air-arrow { stroke-width: 4; opacity: 1; }

.out-arrow {
  fill: none;
  stroke: var(--outdoor);
  stroke-width: 3.2;
  stroke-linecap: round;
  stroke-dasharray: 6 6;
}

#condenser-air.outdoor-air-weak .out-arrow { stroke-width: 1.8; opacity: 0.4; }
#condenser-air.outdoor-air-strong .out-arrow { stroke-width: 3.4; opacity: 1; }

.warm-arrow {
  fill: none;
  stroke: var(--warm);
  stroke-width: 3.2;
  stroke-linecap: round;
  stroke-dasharray: 5 7;
}

#warm-ingress,
#dirt-layer { display: none; }

body.door-ajar #warm-ingress,
body.dirt-on #dirt-layer { display: block; }

body.door-ajar #door-leaf {
  transform: rotate(-16deg);
  transform-origin: 68px 116px;
}

.fan-blades { transform-box: fill-box; transform-origin: center; }

.ref-line {
  fill: none;
  stroke: var(--ref);
  stroke-width: 4;
}

.node { cursor: pointer; }

.node .housing { transition: stroke 0.15s, fill 0.15s; }
.node[data-selected="true"] .housing { stroke: #09644f; stroke-width: 4; }

.number-badge,
.node[data-selected="true"] .number-badge {
  fill: #304c5f;
  stroke: #fff;
  stroke-width: 2;
}

.badge-text {
  fill: #fff;
  font: 600 13px Arial, sans-serif;
  text-anchor: middle;
}

.svg-label {
  fill: var(--ink);
  font-size: 16px;
  font-family: inherit;
}

.svg-label.small { font-size: 14px; }
.section-label { font-size: 18px; font-weight: 650; }
.model-note { fill: var(--muted); font-size: 12px; }
.warm-label { fill: var(--warm); }

figcaption {
  display: flex;
  flex-wrap: wrap;
  gap: 0.5rem 1rem;
  align-items: center;
  margin: 0.6rem 0.2rem 0;
  color: var(--muted);
  font-size: 0.9rem;
}

.legend-item { display: inline-flex; align-items: center; }

.swatch {
  width: 0.85rem;
  height: 0.85rem;
  border-radius: 2px;
  display: inline-block;
  margin-inline-end: 0.3rem;
}

.swatch.air { background: var(--air); }
.swatch.ref { background: var(--ref); }
.swatch.outdoor { background: var(--outdoor); }
.swatch.warm { background: var(--warm); }
.swatch.defect { background: #c9a227; }

.caption { width: 100%; margin: 0; }

.component-legend {
  display: grid;
  grid-template-columns: repeat(2, minmax(0, 1fr));
  gap: 0.4rem;
  margin-top: 1rem;
}

.legend-node {
  display: flex;
  align-items: center;
  gap: 0.6rem;
  padding: 0.65rem;
  border: 1px solid #dbe4e9;
  border-radius: 8px;
  background: #f6f9fb;
  font: inherit;
  text-align: start;
  cursor: pointer;
}

.legend-number {
  background: #304c5f;
  color: #fff;
  border-radius: 50%;
  min-width: 1.55rem;
  height: 1.55rem;
  text-align: center;
  font-size: 0.85rem;
  line-height: 1.55rem;
}

.task-panel { padding: 0.9rem 1rem 1rem; }

.step-meta {
  margin: 0;
  color: var(--muted);
  font-size: 0.82rem;
}

h2 {
  margin: 0.2rem 0 0.35rem;
  font-size: 1.15rem;
}

.lead { margin: 0 0 0.5rem; }

.bounded {
  margin: 0 0 0.7rem;
  padding: 0.4rem 0.55rem;
  background: #f6f8fa;
  border: 1px dashed var(--line);
  border-radius: 8px;
  color: var(--muted);
  font-size: 0.92rem;
}

.choice-list,
.facts-list,
.source-list {
  list-style: none;
  margin: 0;
  padding: 0;
  display: grid;
  gap: 0.45rem;
}

button.choice,
.btn,
.btn-quiet {
  appearance: none;
  font: inherit;
  cursor: pointer;
  border-radius: 8px;
  min-height: 2.4rem;
}

button.choice,
.btn {
  border: 1px solid var(--line);
  background: var(--paper);
  color: var(--ink);
  padding: 0.45rem 0.7rem;
  text-align: start;
}

button.choice[aria-pressed="true"],
.btn.primary {
  border-color: var(--accent);
  background: var(--accent-soft);
}

.btn-quiet {
  border: 1px solid var(--line);
  background: transparent;
  color: var(--ink);
  padding: 0.35rem 0.65rem;
}

.component-controls {
  display: grid;
  grid-template-columns: repeat(2, minmax(0, 1fr));
  gap: 0.5rem;
  margin-block: 0.75rem 1rem;
}

.nav {
  display: flex;
  flex-wrap: wrap;
  gap: 0.45rem;
  margin-top: 0.8rem;
}

.feedback {
  min-height: 1.3em;
  margin: 0.65rem 0;
}

.feedback.is-ok { color: var(--accent); }
.feedback.is-warn { color: var(--warn); }

.facts {
  margin-top: 0.7rem;
  padding-top: 0.55rem;
  border-top: 1px solid var(--line);
}

.facts h3,
.sources h3 {
  margin: 0 0 0.35rem;
  font-size: 0.95rem;
}

.temp-box {
  display: flex;
  flex-wrap: wrap;
  gap: 0.7rem 1.2rem;
  margin: 0.5rem 0;
  padding: 0.55rem 0.65rem;
  background: var(--air-soft);
  border-radius: 8px;
}

.num {
  direction: ltr;
  unicode-bidi: isolate;
  font-variant-numeric: tabular-nums;
}

.model-banner {
  margin: 0.45rem 0;
  padding: 0.4rem 0.55rem;
  border-inline-start: 3px solid var(--warn);
  color: var(--warn);
  font-size: 0.92rem;
}

.trend {
  display: flex;
  align-items: flex-end;
  gap: 0.45rem;
  height: 4.2rem;
  margin: 0.4rem 0 0.2rem;
  direction: ltr;
}

.trend span {
  flex: 1;
  background: var(--air);
  border-radius: 3px 3px 0 0;
  min-width: 1.4rem;
  opacity: 0.28;
}

.trend span.on { opacity: 1; }

.disclaimer {
  margin: 1rem 0 0;
  color: var(--muted);
  font-size: 0.86rem;
}

.source-list a { color: var(--accent); }

:focus-visible {
  outline: 3px solid var(--focus);
  outline-offset: 2px;
}

@media (max-width: 860px) {
  .layout,
  .top { flex-direction: column; }
  .layout { grid-template-columns: 1fr; padding: 0.75rem; }
  .scenario-bar {
    grid-template-columns: 1fr;
    padding: 0.6rem 0.75rem 0;
  }
  .studio-return { padding-inline: 0.75rem; }
  h1 { font-size: 1.2rem; }
  .toolbar { justify-content: flex-start; }
  .legend-node { font-size: 0.9rem; }
}

@media (max-width: 400px) {
  .top,
  .studio-return,
  .layout,
  .scenario-bar { padding-inline: 0.7rem; }
  h1 { font-size: 1.1rem; }
}

@media (prefers-reduced-motion: no-preference) {
  .fan-blades { animation: spin 1.6s linear infinite; }
  #boxes-group { transition: transform 0.45s ease; }
  #air-loop,
  #condenser-air { transition: opacity 0.35s ease; }
  .air-arrow { animation: air-flow 2s linear infinite; }
  #air-loop.air-weak .air-arrow { animation-duration: 5s; }
  .out-arrow { animation: air-flow 1.8s linear infinite; }
  #condenser-air.outdoor-air-weak .out-arrow { animation-duration: 5s; }
  .warm-arrow { animation: air-flow 1.4s linear infinite; }
  #door-leaf { transition: transform 0.35s ease; }
}

@media (prefers-reduced-motion: reduce) {
  .fan-blades { animation: none; }
  #boxes-group,
  #door-leaf { transition: none; }
}

@keyframes spin { to { transform: rotate(360deg); } }
@keyframes air-flow { to { stroke-dashoffset: -32; } }