/* ═══════════════════════════════════════════════════════════
   Rankine & Carnot Cycle Simulator — style.css
   Accent: #f4511e (deep orange — steam / heat)
   ═══════════════════════════════════════════════════════════ */
*, *::before, *::after { box-sizing: border-box; margin: 0; padding: 0; }

:root {
  --bg:        #0d1117;
  --surface:   #161b27;
  --surface2:  #1f2535;
  --border:    #2a3050;
  --accent:    #f4511e;
  --accent-lo: rgba(244,81,30,.22);
  --green:     #3ddc84;
  --red:       #ff5555;
  --gold:      #f5c842;
  --text:      #dde3f0;
  --text-dim:  #6b7a99;
  --font:      'Segoe UI', system-ui, sans-serif;
  --mono:      'Courier New', monospace;
  --radius:    12px;
}

body {
  background: var(--bg);
  color: var(--text);
  font-family: var(--font);
  min-height: 100vh;
  padding: 0 16px;
}

#app {
  max-width: 1400px;
  margin: 0 auto;
  display: flex;
  flex-direction: column;
  gap: 14px;
}

/* ── Header ── */
header { text-align: center; padding: 4px 0; }
header h1 {
  font-size: 1.8rem;
  font-weight: 700;
  background: linear-gradient(120deg, var(--accent) 0%, #ff8a65 100%);
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
  background-clip: text;
}
.subtitle { color: var(--text-dim); font-size: .85rem; margin-top: 3px; }

/* ── Controls bar ── */
.controls-bar {
  display: flex; flex-wrap: wrap; align-items: center; gap: 14px;
  padding: 12px 16px;
  background: var(--surface); border: 1px solid var(--border); border-radius: var(--radius);
}
.ctrl-group { display: flex; align-items: center; gap: 8px; }
.ctrl-label {
  font-size: .72rem; text-transform: uppercase; letter-spacing: .06em;
  color: var(--text-dim); white-space: nowrap;
}

/* ── Pill tabs ── */
.pill-tabs {
  display: flex; background: var(--bg); border-radius: 8px; padding: 3px; gap: 2px;
}
.pill {
  padding: 5px 13px; border: none; background: transparent; color: var(--text-dim);
  border-radius: 6px; cursor: pointer; font-size: .81rem;
  transition: background .18s, color .18s, box-shadow .18s;
}
.pill.active {
  background: var(--accent); color: #fff; box-shadow: 0 0 12px var(--accent-lo);
}
.pill:hover:not(.active) { background: var(--surface2); color: var(--text); }

/* ── Buttons ── */
.btn {
  padding: 8px 18px; border: none; border-radius: 8px; cursor: pointer;
  font-size: .84rem; font-weight: 600;
  transition: filter .18s, box-shadow .18s, opacity .18s;
}
.btn:disabled { opacity: .38; cursor: not-allowed; }
.btn-primary { background: var(--accent); color: #fff; }
.btn-primary:not(:disabled):hover { filter: brightness(1.12); box-shadow: 0 0 12px var(--accent-lo); }
.btn-primary.btn-paused { background: #00838f; }
.btn-primary.btn-paused:not(:disabled):hover { box-shadow: 0 0 12px rgba(0,131,143,.4); }
.btn-ghost { background: var(--surface2); color: var(--text); border: 1px solid var(--border); }
.btn-ghost:hover { background: var(--border); }

/* ── Canvas row ── */
.canvas-row {
  display: flex; gap: 14px; align-items: stretch;
}
.canvas-card {
  background: var(--surface); border: 1px solid var(--border);
  border-radius: var(--radius); padding: 10px;
  overflow-x: clip;
}
.canvas-card canvas {
  display: block; width: 100%; height: auto; touch-action: pan-y;
}
/* Two canvases share the top row; flex ratios chosen so the portrait
   schematic and the landscape diagram render at near-equal heights. */
.canvas-card-machine { flex: 41 1 0; min-width: 0; position: relative; }
.canvas-card-graph   { flex: 59 1 0; min-width: 0; }
.canvas-wrap { position: relative; }

/* Playback controls overlaid on the simulation canvas (bottom-right) */
.canvas-overlay-controls {
  position: absolute; right: 16px; bottom: 16px;
  display: flex; gap: 8px; z-index: 6;
}
.canvas-overlay-controls .btn {
  box-shadow: 0 4px 16px rgba(0,0,0,.55);
  backdrop-filter: blur(2px);
}
@media (max-width: 500px) {
  .canvas-overlay-controls { right: 10px; bottom: 10px; gap: 6px; }
  .canvas-overlay-controls .btn { padding: 7px 12px; font-size: .8rem; }
}

/* Full-width strip under the canvases: live badges, action bar, equation */
.sim-toolbar {
  display: flex; flex-wrap: wrap; align-items: center; gap: 10px 14px;
  padding: 10px 14px;
  background: var(--surface); border: 1px solid var(--border); border-radius: var(--radius);
}
.sim-toolbar .graph-badges { margin-top: 0; flex: 0 1 auto; }
.sim-toolbar .canvas-action-bar { margin-top: 0; padding-top: 0; border-top: none; }
.live-eq {
  margin: 0; padding: 8px 12px; flex: 1; min-width: 240px;
  background: var(--bg); border: 1px solid var(--border); border-radius: 8px;
  font-family: var(--mono); font-size: .78rem; color: var(--accent); line-height: 1.5;
}

/* ── Diagram toggle row (below canvas, above badges) ── */
.canvas-toggles {
  display: flex; flex-wrap: wrap; gap: 4px 10px;
  padding: 4px 2px; align-items: center;
}
.cv-tog {
  display: inline-flex; align-items: center; gap: 5px;
  font-size: 0.73rem; color: var(--text-dim); cursor: pointer;
  user-select: none; padding: 2px 4px; border-radius: 4px;
}
.cv-tog:hover { background: rgba(255,255,255,0.05); color: var(--text); }
.cv-tog input { accent-color: var(--accent); width: 13px; height: 13px; cursor: pointer; }

/* ── Machine canvas toggle panel (below canvas) ── */
.mc-toggles {
  display: flex; flex-wrap: wrap; align-items: center; gap: 5px 10px;
  padding: 7px 10px 5px;
  border-top: 1px solid var(--border);
  margin-top: 6px;
}
.mc-tog-label {
  font-size: 0.68rem; text-transform: uppercase; letter-spacing: 0.06em;
  color: var(--text-dim); white-space: nowrap; flex-shrink: 0;
}

/* ── Graph badges ── */
.graph-badges {
  display: flex; gap: 8px; flex-wrap: wrap; margin-top: 8px;
}
.graph-badge {
  display: flex; align-items: center; gap: 5px;
  padding: 4px 10px;
  background: var(--surface2); border: 1px solid var(--border); border-radius: 8px;
  font-size: .72rem; color: var(--text-dim);
}
.graph-badge-val {
  font-family: var(--mono); font-weight: 700; color: var(--text); font-size: .78rem;
}

/* ── Inline speed control inside graph-badges row ── */
.graph-badge-speed {
  display: flex; align-items: center; gap: 6px;
  flex: 1; min-width: 120px;
  padding: 4px 10px;
  background: var(--surface2); border: 1px solid var(--border); border-radius: 8px;
  font-size: .72rem; color: var(--text-dim);
}
.speed-label { white-space: nowrap; flex-shrink: 0; }
.speed-inline-slider {
  flex: 1; min-width: 60px; max-width: 160px;
  -webkit-appearance: none; appearance: none;
  height: 4px; background: var(--border); border-radius: 2px; outline: none; cursor: pointer;
}
.speed-inline-slider::-webkit-slider-thumb {
  -webkit-appearance: none; width: 13px; height: 13px;
  border-radius: 50%; background: var(--accent); cursor: pointer;
  border: 2px solid var(--bg);
}
.speed-inline-slider::-moz-range-thumb {
  width: 13px; height: 13px; border-radius: 50%; background: var(--accent);
  cursor: pointer; border: 2px solid var(--bg);
}
.speed-val-text {
  font-family: var(--mono); font-weight: 700; color: var(--accent); font-size: .78rem;
  white-space: nowrap; min-width: 3ch; text-align: right;
}

/* ── Controls panel — full-width responsive grid under the canvases ── */
.sim-controls {
  display: grid;
  grid-template-columns: repeat(3, minmax(0, 1fr));
  gap: 8px 12px;
  padding: 10px 14px;
  background: var(--surface); border: 1px solid var(--border); border-radius: var(--radius);
  align-content: start;
}
.ctrl-top-row {
  grid-column: 1 / -1;
  display: grid; grid-template-columns: 1fr auto;
  gap: 8px; align-items: center;
}
.ctrl-preset-group { display: flex; align-items: center; gap: 6px; flex-shrink: 0; }
.ref-tabs { display: flex; gap: 6px; flex-wrap: wrap; }

/* ── Cycle-type chips ── */
.mat-pill {
  display: inline-flex; align-items: center; gap: 6px;
  padding: 5px 13px;
  border: 1.5px solid var(--chip-col, var(--border));
  border-radius: 20px;
  background: transparent;
  color: var(--text-dim);
  cursor: pointer;
  font-size: .76rem; font-weight: 500;
  letter-spacing: .02em;
  transition: background .18s, color .18s, box-shadow .18s;
  white-space: nowrap;
}
.mat-pill::before {
  content: '';
  display: block;
  width: 7px; height: 7px;
  border-radius: 50%;
  background: var(--chip-col, var(--accent));
  flex-shrink: 0;
}
.mat-pill.active {
  background: var(--chip-col, var(--accent));
  border-color: var(--chip-col, var(--accent));
  color: #0d1117;
  font-weight: 700;
  box-shadow: 0 0 12px var(--chip-col, var(--accent));
}
.mat-pill:hover:not(.active) {
  background: rgba(255,255,255,.06);
  color: var(--text);
}

/* ── Stepper slider groups — 2-row compact layout ── */
.sim-slider-group {
  display: flex; flex-direction: column; gap: 5px; min-width: 0;
  background: var(--bg); border: 1px solid var(--border);
  border-radius: 8px; padding: 6px 8px 7px;
}
.sim-slider-group.disabled { opacity: .4; pointer-events: none; }
.sim-slider-header {
  display: flex; align-items: center; gap: 5px;
}
.sim-slider-label {
  font-size: 0.68rem; font-weight: 700; color: var(--text-dim);
  flex: 1; white-space: nowrap; overflow: hidden; text-overflow: ellipsis;
}
.sim-derived-row {
  display: flex; justify-content: space-between; align-items: center;
  font-size: 0.67rem; padding: 0 1px 1px;
}
.sim-derived-label { color: var(--text-dim); }
.sim-derived-val { color: var(--accent); font-family: var(--mono); font-weight: 700; font-size: 0.72rem; }
.sim-unit-badge {
  display: inline-flex; align-items: center;
  padding: 0 6px; height: 22px; border-radius: 5px;
  background: var(--accent-lo); color: var(--accent);
  font-size: 0.64rem; font-weight: 700; flex-shrink: 0;
}
.sim-slider {
  width: 100%; -webkit-appearance: none; appearance: none;
  height: 6px; background: rgba(255,255,255,.12); border-radius: 3px;
  outline: none; border: none; cursor: pointer;
  padding: 6px 0; box-sizing: content-box;
}
.sim-slider::-webkit-slider-runnable-track {
  height: 6px; border-radius: 3px;
  background: linear-gradient(to right, var(--accent-lo), rgba(255,255,255,.12));
}
.sim-slider::-webkit-slider-thumb {
  -webkit-appearance: none; width: 16px; height: 16px; margin-top: -5px;
  border-radius: 50%; background: var(--accent); cursor: grab;
  box-shadow: 0 0 8px var(--accent-lo); border: 2px solid rgba(255,255,255,.25);
}
.sim-slider:active::-webkit-slider-thumb { cursor: grabbing; }
.sim-slider::-moz-range-track {
  height: 6px; border-radius: 3px;
  background: linear-gradient(to right, var(--accent-lo), rgba(255,255,255,.12));
}
.sim-slider::-moz-range-thumb {
  width: 14px; height: 14px; border: 2px solid rgba(255,255,255,.25);
  border-radius: 50%; background: var(--accent); cursor: grab;
}
.stepper {
  display: flex; align-items: stretch; flex-shrink: 0;
  border: 1px solid var(--border); border-radius: 5px; overflow: hidden;
  background: var(--bg); height: 22px;
}
.step-btn {
  width: 22px; flex-shrink: 0; border: none; background: var(--surface2);
  color: var(--text-dim); font-size: 0.88rem; font-weight: 700;
  cursor: pointer; transition: background .15s, color .15s;
  display: flex; align-items: center; justify-content: center; padding: 0;
  min-width: 22px;
}
.step-btn:hover { background: var(--accent-lo); color: var(--accent); }
.step-btn:active { background: var(--accent); color: #0d1117; }
.step-input {
  width: 44px; flex: none; border: none; background: var(--bg); color: var(--accent);
  font-family: var(--mono); font-size: 0.75rem; font-weight: 700;
  text-align: center; outline: none; padding: 0; height: 100%;
  border-left: 1px solid var(--border); border-right: 1px solid var(--border);
}
.step-input:focus { background: var(--surface2); }
.step-input::-webkit-outer-spin-button,
.step-input::-webkit-inner-spin-button { -webkit-appearance: none; margin: 0; }
.step-input[type=number] { -moz-appearance: textfield; }

/* ── Preset select ── */
.preset-select {
  padding: 5px 10px; border: 1px solid var(--border); border-radius: 8px;
  background: var(--surface2); color: var(--text); font-size: .76rem;
  cursor: pointer; outline: none;
}
.preset-select:focus { border-color: var(--accent); }

/* ── Canvas action bar ── */
.canvas-action-bar {
  display: flex; gap: 8px; flex-wrap: wrap; align-items: center;
  margin-top: 8px; padding-top: 8px;
  border-top: 1px solid var(--border);
}

/* ── Segmented toggle (units + diagram type) ── */
.unit-toggle {
  display: inline-flex; border: 1px solid var(--border); border-radius: 8px;
  overflow: hidden; flex-shrink: 0;
}
.unit-opt {
  padding: 6px 13px; border: none; background: var(--surface2);
  color: var(--text-dim); font-size: .82rem; font-weight: 600;
  cursor: pointer; transition: background .15s, color .15s; line-height: 1;
}
.unit-opt + .unit-opt { border-left: 1px solid var(--border); }
.unit-opt.active { background: var(--accent); color: #0d1117; font-weight: 700; }
.unit-opt:not(.active):hover { background: var(--border); color: var(--text); }

/* ── Right-click context menu ── */
.ph-ctx-menu {
  position: fixed; display: none; z-index: 9999;
  background: var(--surface2); border: 1px solid var(--border); border-radius: 8px;
  padding: 4px 0; min-width: 180px;
  box-shadow: 0 8px 24px rgba(0,0,0,.55);
}
.ctx-item {
  display: block; width: 100%; padding: 8px 14px;
  background: transparent; border: none; color: var(--text);
  font-size: .82rem; text-align: left; cursor: pointer;
  transition: background .15s;
}
.ctx-item:hover { background: var(--border); }

/* ── Readout grid ── */
.readout-grid {
  display: grid; grid-template-columns: repeat(4, 1fr); gap: 10px;
  padding: 12px 16px;
  background: var(--surface); border: 1px solid var(--border); border-radius: var(--radius);
}
.readout-card {
  background: var(--surface2); border: 1px solid var(--border); border-radius: 8px;
  padding: 10px 12px; text-align: center;
}
.readout-card.highlight { border-color: var(--accent); box-shadow: 0 0 10px var(--accent-lo); }
.readout-label { font-size: .66rem; text-transform: uppercase; letter-spacing: .04em; color: var(--text-dim); margin-bottom: 4px; }
.readout-value { font-family: var(--mono); font-size: 1.1rem; font-weight: 700; color: var(--accent); }
.readout-unit  { font-size: .68rem; color: var(--text-dim); margin-top: 2px; }

/* ── State-point table ── */
.state-table-card {
  padding: 12px 16px;
  background: var(--surface); border: 1px solid var(--border); border-radius: var(--radius);
  overflow-x: auto;
}
.state-table-title {
  font-size: .72rem; text-transform: uppercase; letter-spacing: .06em;
  color: var(--text-dim); margin-bottom: 8px;
}
.state-table { width: 100%; border-collapse: collapse; font-size: .8rem; }
.state-table th {
  text-align: right; padding: 6px 10px; border-bottom: 1px solid var(--border);
  color: var(--text-dim); font-weight: 700; white-space: nowrap;
}
.state-table th:first-child, .state-table td:first-child { text-align: left; }
.state-table td {
  padding: 6px 10px; border-bottom: 1px solid var(--border);
  font-family: var(--mono); text-align: right; white-space: nowrap;
}
.state-table tbody tr:hover { background: rgba(255,255,255,.03); }
.state-table .st-pt { color: var(--accent); font-weight: 700; }

/* ── Explore mode ── */
.explore-cats {
  display: flex; gap: 4px; flex-wrap: wrap; margin-bottom: 10px;
}
.explore-grid {
  display: grid; grid-template-columns: repeat(auto-fill, minmax(155px, 1fr));
  gap: 8px; margin-bottom: 14px;
}
.explore-btn {
  padding: 8px 10px; background: var(--surface2); border: 1px solid var(--border);
  border-radius: 8px; color: var(--text-dim); cursor: pointer; font-size: .78rem;
  text-align: left; transition: all .18s;
}
.explore-btn.active { background: var(--accent); color: #fff; border-color: var(--accent); }
.explore-btn:hover:not(.active) { border-color: var(--accent); color: var(--text); }
.explore-info {
  background: var(--surface); border: 1px solid var(--border); border-radius: var(--radius);
  padding: 16px 20px; margin-bottom: 14px;
}
.explore-info h3 { font-size: 1rem; color: var(--accent); margin-bottom: 6px; }
.explore-info p  { font-size: .84rem; color: var(--text-dim); line-height: 1.55; }
.explore-info .formula-box {
  margin-top: 10px; padding: 10px 14px;
  background: var(--bg); border: 1px solid var(--border); border-radius: 8px;
  font-family: var(--mono); font-size: .82rem; color: var(--accent); overflow-x: auto;
}
.explore-info .example-box {
  margin-top: 10px; padding: 10px 14px;
  background: var(--bg); border: 1px solid var(--border); border-radius: 8px;
  font-size: .8rem; color: var(--text-dim); line-height: 1.5;
}
.explore-info .example-box strong { color: var(--text); }
.explore-canvas-card {
  background: var(--surface); border: 1px solid var(--border);
  border-radius: var(--radius); padding: 10px;
  overflow-x: clip;
}
.explore-canvas-card canvas { display: block; width: 100%; height: auto; touch-action: pan-y; }

/* ── Practice mode ── */
.practice-panel {
  background: var(--surface); border: 1px solid var(--border); border-radius: var(--radius);
  padding: 18px 22px;
}
.practice-prompt { font-size: .92rem; line-height: 1.5; margin-bottom: 14px; }
.practice-input-row { display: flex; gap: 8px; align-items: center; margin-bottom: 10px; }
.practice-input-row input {
  width: 130px; padding: 6px 10px; border: 1px solid var(--border); border-radius: 6px;
  background: var(--bg); color: var(--text); font-family: var(--mono); font-size: .88rem;
}
.practice-input-row .unit { font-size: .78rem; color: var(--text-dim); }
.practice-feedback { font-size: .86rem; font-weight: 600; margin-bottom: 8px; min-height: 1.2em; }
.practice-feedback.ok  { color: var(--green); }
.practice-feedback.err { color: var(--red); }
.practice-solution {
  display: none; margin-top: 10px; padding: 12px 14px;
  background: var(--bg); border: 1px solid var(--border); border-radius: 8px;
  font-size: .82rem; line-height: 1.6; color: var(--text-dim);
}
.practice-solution strong { color: var(--text); }
.practice-btns { display: flex; gap: 8px; margin-top: 12px; flex-wrap: wrap; }
.practice-score { font-size: .82rem; color: var(--text-dim); margin-left: auto; align-self: center; }
.practice-score span { color: var(--text); font-weight: 700; }

/* ── Quiz mode ── */
.quiz-panel {
  background: var(--surface); border: 1px solid var(--border); border-radius: var(--radius);
  padding: 18px 22px;
}
.quiz-counter { font-size: .74rem; color: var(--text-dim); margin-bottom: 8px; }
.quiz-prompt { font-size: .92rem; line-height: 1.5; margin-bottom: 14px; }
.quiz-options { display: grid; grid-template-columns: 1fr 1fr; gap: 8px; margin-bottom: 12px; }
.quiz-opt {
  padding: 10px 14px; background: var(--surface2); border: 1px solid var(--border);
  border-radius: 8px; cursor: pointer; font-size: .82rem; color: var(--text);
  transition: all .18s; text-align: left;
}
.quiz-opt:hover { border-color: var(--accent); }
.quiz-opt.correct { background: rgba(61,220,132,.15); border-color: var(--green); color: var(--green); }
.quiz-opt.wrong   { background: rgba(255,85,85,.15); border-color: var(--red); color: var(--red); }
.quiz-opt.disabled { pointer-events: none; opacity: .6; }
.quiz-num-row { display: flex; gap: 8px; align-items: center; margin-bottom: 12px; }
.quiz-num-row input {
  width: 130px; padding: 6px 10px; border: 1px solid var(--border); border-radius: 6px;
  background: var(--bg); color: var(--text); font-family: var(--mono); font-size: .88rem;
}
.quiz-feedback { font-size: .86rem; font-weight: 600; min-height: 1.2em; margin-bottom: 8px; }
.quiz-feedback.ok  { color: var(--green); }
.quiz-feedback.err { color: var(--red); }
.quiz-btns { display: flex; gap: 8px; }
.quiz-result {
  display: none;
  background: var(--surface); border: 1px solid var(--border); border-radius: var(--radius);
  padding: 20px 22px;
}
.qr-title { font-size: 1rem; font-weight: 700; margin-bottom: 4px; }
.qr-stars { font-size: 1.4rem; margin-bottom: 6px; }
.qr-score { font-size: .92rem; font-weight: 700; margin-bottom: 12px; }
.qr-score.perfect { color: var(--gold); }
.qr-score.good    { color: var(--green); }
.qr-score.poor    { color: var(--red); }
.qr-table { width: 100%; border-collapse: collapse; font-size: .8rem; margin-bottom: 14px; }
.qr-table th { text-align: left; padding: 6px 8px; border-bottom: 1px solid var(--border); color: var(--text-dim); }
.qr-table td { padding: 6px 8px; border-bottom: 1px solid var(--border); }
.qr-row.ok  { border-left: 3px solid var(--green); }
.qr-row.err { border-left: 3px solid var(--red); }

/* ── User guide ── */
.user-guide {
  background: var(--surface); border: 1px solid var(--border); border-radius: var(--radius);
  padding: 18px 22px;
}
.user-guide-title { font-size: 1.05rem; font-weight: 700; margin-bottom: 12px; display: flex; align-items: center; gap: 8px; }
.guide-icon-badge { font-size: 1.1rem; }
.user-guide details {
  border: 1px solid var(--border); border-radius: 8px; margin-bottom: 8px;
  background: var(--bg); overflow: hidden;
}
.user-guide summary {
  cursor: pointer; padding: 10px 14px; font-size: .88rem; font-weight: 600;
  color: var(--text); display: flex; align-items: center; gap: 10px; user-select: none;
}
.user-guide summary:hover { background: var(--surface2); }
.guide-section-num {
  display: inline-flex; align-items: center; justify-content: center;
  width: 22px; height: 22px; border-radius: 50%; background: var(--accent-lo);
  color: var(--accent); font-size: .72rem; font-weight: 700; flex-shrink: 0;
}
.guide-content { padding: 4px 16px 14px; font-size: .84rem; color: var(--text-dim); line-height: 1.6; }
.guide-content p { margin-bottom: 8px; }
.guide-content ul { margin: 6px 0 8px 18px; }
.guide-content li { margin-bottom: 5px; }
.guide-content strong { color: var(--text); }

/* ── SEO article ── */
.seo-article {
  margin-top: 20px; padding: 24px;
  background: var(--surface); border: 1px solid var(--border); border-radius: var(--radius);
  line-height: 1.65; color: var(--text-dim); font-size: .88rem;
}
.seo-article h2 { font-size: 1.2rem; color: var(--text); margin-bottom: 10px; }
.seo-article h3 { font-size: 1rem; color: var(--text); margin: 16px 0 6px; }
.seo-article p  { margin-bottom: 10px; }
.seo-article table { width: 100%; border-collapse: collapse; margin: 10px 0; font-size: .82rem; }
.seo-article th, .seo-article td { padding: 6px 10px; border: 1px solid var(--border); text-align: left; }
.seo-article th { background: var(--surface2); color: var(--text); }
.seo-article ul { margin: 8px 0 12px 20px; }
.seo-article li { margin-bottom: 5px; }
.author-byline {
  display: flex; align-items: center; gap: 12px; margin-bottom: 18px;
  padding: 12px 14px; background: var(--bg); border: 1px solid var(--border); border-radius: 8px;
}
.author-byline img { border-radius: 50%; flex-shrink: 0; }
.byline-row1 { font-size: .82rem; color: var(--text); }
.byline-row2 { font-size: .76rem; color: var(--text-dim); margin-top: 2px; }
.byline-row3 { font-size: .74rem; margin-top: 2px; }
.author-byline a { color: var(--accent); text-decoration: none; }
.author-byline a:hover { text-decoration: underline; }
.further-reading {
  margin-top: 16px; padding: 12px 16px; background: var(--bg);
  border: 1px solid var(--border); border-left: 3px solid var(--accent); border-radius: 8px;
  font-size: .84rem;
}
.further-reading a { color: var(--accent); }

/* ── Footer ── */
.site-footer { margin-top: 24px; padding: 18px 0; border-top: 1px solid var(--border); text-align: center; }
.site-footer-nav { display: flex; gap: 16px; justify-content: center; flex-wrap: wrap; margin-bottom: 8px; }
.site-footer-nav a { color: var(--text-dim); font-size: .8rem; text-decoration: none; }
.site-footer-nav a:hover { color: var(--accent); }
.site-footer-copy { font-size: .76rem; color: var(--text-dim); }

/* ── Mode wrappers (hidden by default; JS toggles) ── */
.explore-wrapper, .practice-wrapper, .quiz-wrapper { display: none; }

/* ── Responsive ── */
@media (max-width: 1200px) {
  .canvas-row { flex-direction: column; }
  .canvas-card-machine, .canvas-card-graph { flex: none; }
}
@media (max-width: 768px) {
  .readout-grid { grid-template-columns: 1fr 1fr; }
  .sim-controls { grid-template-columns: 1fr 1fr; gap: 8px 10px; }
  .quiz-options { grid-template-columns: 1fr; }
}
@media (max-width: 500px) {
  header h1 { font-size: 1.4rem; }
  .subtitle { font-size: .78rem; }
  .readout-grid { grid-template-columns: 1fr; }
  .controls-bar { padding: 10px 12px; gap: 8px; }
  .pill { padding: 5px 10px; font-size: .76rem; }
  .sim-controls { grid-template-columns: 1fr; padding: 10px 12px; }
  .canvas-action-bar .btn { flex: 1; }
}