/* ── UTM Virtual Lab ──────────────────────────────────────────── */

/* ── Reset & Tokens ── */
*, *::before, *::after { box-sizing: border-box; margin: 0; padding: 0; }
:root {
  --bg: #0d1117; --surface: #161b27; --surface2: #1f2535; --border: #2a3050;
  --accent: #1e88e5; --accent-lo: rgba(30,136,229,.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 & App ───────────────────────────────────────────────── */
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, #1e88e5 0%, #64b5f6 100%);
  -webkit-background-clip: text; -webkit-text-fill-color: transparent; background-clip: text;
}
.subtitle { color: var(--text-dim); font-size: 0.85rem; 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: 0.72rem; text-transform: uppercase; letter-spacing: .06em; color: var(--text-dim); white-space: nowrap; font-weight: 600; }

/* ── 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: 0.81rem;
  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); }

/* ── Dual Canvas Row ──────────────────────────────────────────── */
.dual-canvas-row {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 14px;
  align-items: start;
}

/* ── Canvas card ──────────────────────────────────────────────── */
.canvas-card {
  width: 100%; background: var(--surface);
  border: 1px solid var(--border); border-radius: var(--radius);
  padding: 8px; position: relative; overflow: hidden;
}
.canvas-card canvas { display: block; width: 100%; height: auto; cursor: pointer; touch-action: pan-y; }

/* ── Lab Procedure Panel ──────────────────────────────────────── */
.lab-procedure {
  background: var(--surface); border: 1px solid var(--border);
  border-radius: var(--radius); padding: 14px 18px;
}
.lab-steps { display: flex; gap: 6px; flex-wrap: wrap; }
.lab-step {
  display: flex; align-items: center; gap: 6px;
  padding: 5px 12px; border: 2px solid var(--border); border-radius: 8px;
  background: var(--surface2); font-size: 0.72rem; font-weight: 600;
  color: var(--text-dim); transition: all .2s; cursor: default; white-space: nowrap;
}
.lab-step.active { border-color: var(--accent); color: var(--accent); background: var(--accent-lo); }
.lab-step.done { border-color: var(--green); color: var(--green); }
.lab-step-num {
  width: 20px; height: 20px; border-radius: 50%; background: var(--border);
  display: flex; align-items: center; justify-content: center;
  font-size: 0.65rem; font-weight: 700; color: var(--text-dim);
}
.lab-step.active .lab-step-num { background: var(--accent); color: #fff; }
.lab-step.done .lab-step-num { background: var(--green); color: #fff; }

/* ── Sim Controls Panel ───────────────────────────────────────── */
.sim-controls {
  background: var(--surface); border: 1px solid var(--border); border-radius: var(--radius);
  padding: 14px 18px; display: flex; flex-wrap: wrap; gap: 14px; align-items: flex-end;
}
.sim-controls .ctrl-group { display: flex; flex-direction: column; gap: 4px; }
.sim-controls .ctrl-label { font-size: 0.68rem; text-transform: uppercase; letter-spacing: .06em; color: var(--text-dim); font-weight: 600; }

/* ── Hidden slider (kept for JS stepper logic) ───────────────── */
.slider { display: none; }

/* ── Readout Grid (results) ───────────────────────────────────── */
.readout-row {
  display: grid; grid-template-columns: repeat(4, 1fr); gap: 10px;
}
.readout-card {
  background: var(--surface); border: 1px solid var(--border); border-radius: var(--radius);
  padding: 12px 14px; text-align: center;
}
.readout-label {
  font-size: 0.68rem; text-transform: uppercase; letter-spacing: .05em;
  color: var(--text-dim); margin-bottom: 4px;
}
.readout-value {
  font-size: 1.1rem; font-weight: 700; color: var(--text); font-family: var(--mono);
}
.readout-unit { font-size: 0.7rem; color: var(--text-dim); margin-left: 2px; }

/* ── Live Readout Strip ───────────────────────────────────────── */
.live-strip {
  display: flex; gap: 2px; margin-top: 6px;
  background: var(--bg); border-radius: 8px; padding: 4px 6px;
  border: 1px solid var(--border);
}
.ls-item {
  flex: 1; display: flex; align-items: center; gap: 5px;
  padding: 3px 8px; border-radius: 6px;
  justify-content: center;
}
.ls-label {
  font-size: 0.58rem; text-transform: uppercase; letter-spacing: .04em;
  color: var(--text-dim); font-weight: 600;
}
.ls-val {
  font-size: 0.82rem; font-weight: 700; color: var(--accent); font-family: var(--mono);
}

/* ── Buttons ──────────────────────────────────────────────────── */
.btn {
  padding: 8px 18px; border: none; border-radius: 8px; cursor: pointer;
  font-size: 0.84rem; font-weight: 600; transition: filter .18s, box-shadow .18s, opacity .18s;
}
.btn:disabled { opacity: 0.38; 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-ghost { background: var(--surface2); color: var(--text); border: 1px solid var(--border); }
.btn-ghost:hover { background: var(--border); }
.btn-danger { background: var(--red); color: #fff; }
.btn-danger:not(:disabled):hover { filter: brightness(1.12); box-shadow: 0 0 12px rgba(255,85,85,.35); }

/* ── Material pills (small inline tabs) ───────────────────────── */
.material-pills { display: flex; gap: 4px; flex-wrap: wrap; }
.material-pill {
  padding: 4px 10px; border: 2px solid var(--border); border-radius: 8px;
  background: var(--surface2); color: var(--text-dim); font-size: 0.74rem;
  font-weight: 600; cursor: pointer; transition: border-color .18s, color .18s, background .18s;
}
.material-pill:hover { border-color: rgba(30,136,229,.45); color: var(--text); }
.material-pill.active { border-color: var(--accent); color: #fff; background: var(--accent-lo); }

/* ── Test type toggle ─────────────────────────────────────────── */
.test-type-tabs { display: flex; background: var(--bg); border-radius: 8px; padding: 3px; gap: 2px; }
.test-type-tabs .pill.active[data-value="tensile"] { background: var(--accent); }
.test-type-tabs .pill.active[data-value="compression"] { background: #e57c1e; }

/* ── Explore Mode ─────────────────────────────────────────────── */
.item-selector {
  background: var(--surface); border: 1px solid var(--border); border-radius: var(--radius);
  padding: 14px 16px;
}
.is-grid { display: grid; grid-template-columns: repeat(auto-fill, minmax(155px, 1fr)); gap: 8px; margin-top: 10px; }
.is-btn {
  padding: 10px 14px; border: 2px solid var(--border); border-radius: 10px;
  background: var(--surface2); color: var(--text-dim); font-size: 0.82rem;
  font-weight: 600; cursor: pointer; text-align: left;
  transition: border-color .18s, color .18s, background .18s, box-shadow .18s;
}
.is-btn:hover { border-color: rgba(30,136,229,.45); color: var(--text); }
.is-btn.active { border-color: var(--accent); color: #fff; background: rgba(30,136,229,.15); box-shadow: 0 0 14px var(--accent-lo); }
.is-btn-name { display: block; font-size: 0.82rem; font-weight: 700; }
.is-btn-sym  { display: block; font-size: 0.68rem; color: var(--accent); margin-top: 2px; font-family: var(--mono); }

.item-info {
  background: var(--surface); border: 1px solid var(--border); border-radius: var(--radius);
  padding: 16px 18px; display: flex; flex-direction: column; gap: 8px;
}
.ii-top { display: flex; align-items: center; gap: 12px; flex-wrap: wrap; }
.ii-name { font-size: 1.15rem; font-weight: 800; color: var(--text); }
.ii-cat-badge {
  font-size: 0.62rem; font-weight: 700; text-transform: uppercase;
  letter-spacing: .07em; padding: 3px 10px; border-radius: 20px;
  background: var(--accent-lo); color: var(--accent);
}
.ii-desc { font-size: 0.85rem; color: var(--text-dim); line-height: 1.65; }

/* Formula box */
.formula-box {
  background: var(--bg); border: 1px solid var(--border); border-radius: 8px;
  padding: 10px 14px; display: flex; align-items: center; gap: 16px; flex-wrap: wrap;
}
.fb-label { font-size: 0.62rem; text-transform: uppercase; letter-spacing: .07em; color: var(--text-dim); font-weight: 700; }
.fb-formula { font-family: var(--mono); font-size: 1.1rem; font-weight: 700; color: var(--accent); }
.fb-unit { font-size: 0.78rem; color: var(--text-dim); }

/* Example calculation */
.example-box {
  background: var(--surface2); border: 1px solid var(--border); border-radius: 8px;
  padding: 12px 14px;
}
.eb-title { font-size: 0.72rem; text-transform: uppercase; letter-spacing: .08em; color: var(--accent); margin-bottom: 8px; font-weight: 700; }
.eb-body { font-size: 0.84rem; color: var(--text-dim); line-height: 1.65; }
.eb-body strong { color: var(--green); font-family: var(--mono); }

/* ── Practice Mode ────────────────────────────────────────────── */
.practice-panel {
  background: var(--surface); border: 1px solid var(--border); border-radius: var(--radius);
  padding: 16px 18px;
}
.pp-prompt { font-size: 0.92rem; font-weight: 600; color: var(--text); margin-bottom: 14px; line-height: 1.6; }
.pp-input-row { display: flex; align-items: center; gap: 10px; flex-wrap: wrap; }
.qi-input {
  flex: 1; min-width: 120px; max-width: 200px;
  padding: 10px 14px; border: 2px solid var(--border); border-radius: 8px;
  background: var(--bg); color: var(--text); font-family: var(--mono);
  font-size: 1rem; font-weight: 700; transition: border-color .18s;
}
.qi-input:focus { outline: none; border-color: var(--accent); }
.pp-unit { font-size: 0.88rem; color: var(--text-dim); font-weight: 600; }
.feedback { font-size: 0.88rem; font-weight: 600; margin-top: 10px; }
.feedback.ok  { color: var(--green); }
.feedback.err { color: var(--red); }

.practice-bar {
  display: flex; align-items: center; gap: 12px; flex-wrap: wrap;
  padding: 12px 16px;
  background: var(--surface); border: 1px solid var(--border); border-radius: var(--radius);
}
.pbar-score { font-size: 0.84rem; color: var(--text-dim); margin-left: auto; white-space: nowrap; }
.pbar-score span { color: var(--text); font-weight: 700; }

.solution-panel {
  background: var(--surface2); border: 1px solid var(--border); border-radius: 8px;
  padding: 14px 16px; margin-top: 12px;
}
.solution-panel h4 {
  font-size: 0.72rem; text-transform: uppercase; letter-spacing: .08em;
  color: var(--accent); margin-bottom: 8px;
}
.sol-step { font-size: 0.82rem; color: var(--text-dim); line-height: 1.7; padding: 2px 0; }
.sol-step strong { color: var(--green); font-family: var(--mono); }

/* ── Quiz Mode ────────────────────────────────────────────────── */
.question-panel {
  background: var(--surface); border: 1px solid var(--border); border-radius: var(--radius);
  padding: 16px 18px;
}
.qp-header {
  font-size: 0.72rem; text-transform: uppercase; letter-spacing: .06em;
  color: var(--text-dim); font-weight: 700; margin-bottom: 10px;
}
.qp-prompt { font-size: 0.88rem; font-weight: 600; color: var(--text); margin-bottom: 12px; line-height: 1.6; }
.answer-grid { display: grid; grid-template-columns: 1fr 1fr; gap: 10px; }
.answer-btn {
  padding: 14px 16px; border: 2px solid var(--border); border-radius: 10px;
  background: var(--surface2); color: var(--text); font-size: 0.88rem;
  font-weight: 600; cursor: pointer; text-align: center;
  transition: border-color .18s, background .18s, color .18s, transform .12s;
}
.answer-btn:hover:not(.locked) { border-color: var(--accent); background: rgba(30,136,229,.06); }
.answer-btn.correct { border-color: var(--green); background: rgba(61,220,132,.12); color: var(--green); }
.answer-btn.wrong { border-color: var(--red); background: rgba(255,85,85,.08); color: var(--red); }
.answer-btn.locked { cursor: default; opacity: 0.6; }
.answer-btn.correct.locked { opacity: 1; }

.quiz-bar {
  display: flex; align-items: center; gap: 12px; flex-wrap: wrap;
  padding: 12px 16px;
  background: var(--surface); border: 1px solid var(--border); border-radius: var(--radius);
}
.quiz-feedback { font-size: 0.88rem; font-weight: 600; }
.quiz-feedback.ok  { color: var(--green); }
.quiz-feedback.err { color: var(--red); }

/* Quiz result */
.quiz-result {
  background: var(--surface); border: 1px solid var(--border); border-radius: var(--radius);
  padding: 20px 22px; display: flex; flex-direction: column; gap: 14px;
}
.qr-header { display: flex; align-items: flex-start; justify-content: space-between; }
.qr-title-wrap { display: flex; flex-direction: column; gap: 5px; }
.qr-title  { font-size: 1.1rem; font-weight: 700; color: var(--text); }
.qr-stars  { font-size: 1.2rem; letter-spacing: 3px; }
.qr-score-wrap { text-align: right; }
.qr-score {
  font-family: var(--mono); font-size: 2.2rem; font-weight: 700; line-height: 1;
  text-shadow: 0 0 14px currentColor;
}
.qr-score.perfect { color: var(--gold); }
.qr-score.good { color: var(--green); }
.qr-score.poor { color: var(--red); }
.qr-verdict { font-size: 0.72rem; color: var(--text-dim); margin-top: 3px; }
.qr-table { display: flex; flex-direction: column; gap: 7px; }
.qr-row {
  display: grid; grid-template-columns: 30px 1fr 26px; align-items: center; gap: 10px;
  background: var(--surface2); border: 1px solid var(--border); border-left-width: 3px;
  border-radius: 8px; padding: 9px 12px;
}
.qr-row.ok  { border-left-color: var(--green); }
.qr-row.err { border-left-color: var(--red); }
.qr-qnum { font-size: 0.72rem; font-weight: 700; color: var(--accent); }
.qr-detail { font-size: 0.78rem; color: var(--text-dim); }
.qr-detail strong { color: var(--text); }
.qr-mark { text-align: right; font-size: 1rem; font-weight: 700; }
.qr-row.ok .qr-mark { color: var(--green); }
.qr-row.err .qr-mark { color: var(--red); }

/* ── Unified Control Panel ────────────────────────────────────── */
.ctrl-panel {
  margin-top: 8px; padding: 12px 14px;
  background: var(--surface2); border: 1px solid var(--border); border-radius: 10px;
  display: flex; flex-direction: column; gap: 10px;
}
.cp-title {
  font-size: 0.65rem; font-weight: 800; text-transform: uppercase;
  letter-spacing: 0.12em; color: var(--text-dim); opacity: 0.6;
}

/* Row 1: Action buttons */
.cp-actions { display: flex; align-items: center; gap: 8px; flex-wrap: wrap; }
.cp-btn {
  display: flex; align-items: center; gap: 5px;
  padding: 10px 18px; border: 2px solid var(--border); border-radius: 10px;
  background: var(--surface); color: var(--text-dim); font-size: 0.88rem;
  font-weight: 700; cursor: pointer; white-space: nowrap; transition: all .2s ease;
  transition: background .15s, color .15s, border-color .15s, box-shadow .15s;
}
.cp-btn:hover:not(:disabled) { background: var(--accent-lo); color: var(--text); border-color: var(--accent); }
.cp-btn:disabled { opacity: 0.35; cursor: not-allowed; }
.cp-icon { font-size: 1.05rem; }
.cp-mount { color: var(--accent); border-color: rgba(30,136,229,.45); background: rgba(30,136,229,.08); }
.cp-mount:hover:not(:disabled) { background: var(--accent); color: #fff; box-shadow: 0 0 14px var(--accent-lo); }
.cp-start { color: var(--green); border-color: rgba(61,220,132,.45); background: rgba(61,220,132,.08); }
.cp-start:hover:not(:disabled) { background: var(--green); color: #fff; box-shadow: 0 0 14px rgba(61,220,132,.3); }
.cp-reset { color: var(--text-dim); }
.cp-export { color: var(--gold); border-color: rgba(245,200,66,.25); font-size: 0.78rem; padding: 8px 14px; }
.cp-export:hover { background: rgba(245,200,66,.1); border-color: var(--gold); color: var(--gold); }

/* Guide blink — yellow border pulse on the next-action button */
@keyframes guideBlink {
  0%, 100% { border-color: rgba(245,200,66,.15); box-shadow: 0 0 0 rgba(245,200,66,0); }
  50% { border-color: rgba(245,200,66,.9); box-shadow: 0 0 12px rgba(245,200,66,.35); }
}
.cp-guide-blink:not(:disabled) {
  animation: guideBlink 1.4s ease-in-out infinite;
}
.cp-spacer { flex: 1; }
.cp-sep { width: 1px; height: 32px; background: var(--border); margin: 0 4px; flex-shrink: 0; }
.cp-test-type { background: var(--bg); border-radius: 10px; padding: 3px; }
.cp-test-type .pill { font-size: 0.84rem; padding: 8px 16px; font-weight: 700; }
.cp-test-type .pill.active[data-value="tensile"] { background: var(--accent); color: #fff; box-shadow: 0 0 10px var(--accent-lo); }
.cp-test-type .pill.active[data-value="compression"] { background: #e57c1e; color: #fff; box-shadow: 0 0 10px rgba(229,124,30,.3); }

/* Divider between actions and config */
.cp-sep-h { width: 100%; height: 1px; background: var(--border); }

/* Row 2: Material + params */
.cp-config { display: flex; flex-direction: column; gap: 8px; }
.cp-material { display: flex; flex-direction: column; gap: 4px; }
.cp-label {
  font-size: 0.62rem; text-transform: uppercase; letter-spacing: .06em;
  color: var(--text-dim); font-weight: 600; white-space: nowrap;
}

/* Material strip — compact scrollable row */
.mat-strip {
  display: flex; gap: 3px; flex-wrap: wrap;
  background: var(--bg); border-radius: 8px; padding: 3px;
  flex: 1; min-width: 0;
}
.mat-strip .pill {
  padding: 3px 8px; font-size: 0.68rem; font-weight: 600; border-radius: 5px;
  white-space: nowrap;
}

/* Params row */
.cp-params { display: flex; gap: 10px; flex-wrap: wrap; align-items: flex-end; }
.cp-field { display: flex; flex-direction: column; gap: 3px; min-width: 0; flex: 1; }
.cp-field .slider { width: 100%; min-width: 70px; }

/* ── Stepper Input with Fill Bar ──────────────────────────────── */
.stepper-row {
  display: flex; align-items: stretch; gap: 0; border: 1px solid var(--border);
  border-radius: 8px; overflow: hidden; background: var(--bg);
}
.stepper-btn {
  width: 36px; min-height: 36px; border: none; background: var(--surface2);
  color: var(--accent); font-size: 1.1rem; font-weight: 700; cursor: pointer;
  transition: background .15s; flex-shrink: 0;
}
.stepper-dec { border-right: 1px solid var(--border); }
.stepper-inc { border-left: 1px solid var(--border); }
.stepper-btn:hover { background: var(--accent-lo); }
.stepper-btn:active { background: var(--accent); color: #fff; }
.stepper-track {
  flex: 1; position: relative; min-width: 0; display: flex;
  align-items: center; justify-content: center;
}
.stepper-fill {
  position: absolute; left: 0; top: 0; bottom: 0; width: 0%;
  background: linear-gradient(90deg, rgba(30,136,229,.55) 0%, rgba(30,136,229,.3) 100%);
  border-right: 2px solid rgba(30,136,229,.7);
  transition: width .25s ease; pointer-events: none;
}
.stepper-input {
  width: 100%; height: 36px; border: none; background: transparent; color: var(--text);
  text-align: center; font-family: var(--mono); font-size: 0.85rem; font-weight: 700;
  -moz-appearance: textfield; position: relative; z-index: 1;
}
.stepper-input::-webkit-outer-spin-button,
.stepper-input::-webkit-inner-spin-button { -webkit-appearance: none; margin: 0; }
.stepper-input:focus { outline: none; background: rgba(30,136,229,.08); }

/* ── Context Menu ─────────────────────────────────────────────── */
.ctx-menu {
  position: fixed; z-index: 100; min-width: 180px;
  background: var(--surface); border: 1px solid var(--border);
  border-radius: 10px; padding: 4px; box-shadow: 0 8px 24px rgba(0,0,0,.45);
  font-size: 0.8rem;
}
.ctx-item {
  display: flex; align-items: center; gap: 8px;
  padding: 8px 12px; border-radius: 7px; cursor: pointer;
  color: var(--text); transition: background .12s;
}
.ctx-item:hover { background: var(--accent-lo); }
.ctx-item-icon { width: 16px; text-align: center; font-size: 0.9rem; }
.ctx-sep { height: 1px; background: var(--border); margin: 3px 8px; }

/* ── Export Row ───────────────────────────────────────────────── */
.export-row {
  display: flex; gap: 10px; flex-wrap: wrap; padding: 8px 0;
}

/* ── Custom Material Modal ────────────────────────────────────── */
.cm-overlay {
  position: fixed; inset: 0; z-index: 200;
  background: rgba(0,0,0,0.65); display: flex;
  align-items: center; justify-content: center;
  animation: cmFadeIn .2s ease;
}
@keyframes cmFadeIn { from { opacity: 0; } to { opacity: 1; } }
.cm-modal {
  background: var(--surface); border: 1px solid var(--border);
  border-radius: 14px; padding: 22px 26px; width: 420px; max-width: 94vw;
  max-height: 90vh; overflow-y: auto; box-shadow: 0 12px 40px rgba(0,0,0,.5);
}
.cm-title {
  font-size: 1rem; font-weight: 700; color: var(--text); margin-bottom: 4px;
}
.cm-subtitle {
  font-size: 0.72rem; color: var(--text-dim); margin-bottom: 14px;
}
.cm-grid {
  display: grid; grid-template-columns: 1fr 1fr; gap: 10px;
}
.cm-field { display: flex; flex-direction: column; gap: 3px; }
.cm-field.full { grid-column: 1 / -1; }
.cm-label {
  font-size: 0.68rem; text-transform: uppercase; letter-spacing: .05em;
  color: var(--text-dim); font-weight: 600;
}
.cm-range {
  font-size: 0.6rem; color: var(--accent); font-family: var(--mono);
}
.cm-input {
  padding: 8px 10px; border: 1px solid var(--border); border-radius: 8px;
  background: var(--bg); color: var(--text); font-family: var(--mono);
  font-size: 0.85rem; font-weight: 600;
  transition: border-color .15s;
}
.cm-input:focus { outline: none; border-color: var(--accent); }
.cm-input.error { border-color: var(--red); }
.cm-error-msg {
  font-size: 0.68rem; color: var(--red); min-height: 16px; margin-top: 6px;
}
.cm-actions {
  display: flex; gap: 8px; margin-top: 14px; justify-content: flex-end;
}
.cm-actions .btn { min-width: 90px; }

/* ── SEO Article ──────────────────────────────────────────────── */
.seo-article {
  background: var(--surface); border: 1px solid var(--border); border-radius: var(--radius);
  padding: 22px 24px; line-height: 1.75;
}
.seo-article h2 { font-size: 1.2rem; font-weight: 700; color: var(--text); margin-bottom: 12px; }
.seo-article h3 { font-size: 1rem; font-weight: 700; color: var(--accent); margin: 16px 0 6px; }
.seo-article p { font-size: 0.88rem; color: var(--text-dim); margin-bottom: 10px; }

/* ── Responsive ───────────────────────────────────────────────── */
@media (max-width: 1200px) {
  #app { max-width: 980px; }
  .dual-canvas-row { grid-template-columns: 1fr; }
}
@media (max-width: 768px) {
  .readout-row { grid-template-columns: repeat(2, 1fr); }
  .lab-steps { gap: 4px; }
  .sim-controls { gap: 10px; }
  .answer-grid { grid-template-columns: 1fr 1fr; }
  .is-grid { grid-template-columns: repeat(auto-fill, minmax(130px, 1fr)); }
}
@media (max-width: 500px) {
  header h1 { font-size: 1.4rem; }
  .subtitle { font-size: 0.78rem; }
  .controls-bar { padding: 10px 12px; gap: 8px; }
  .pill { padding: 5px 10px; font-size: 0.76rem; }
  .readout-row { grid-template-columns: 1fr 1fr; }
  .answer-grid { grid-template-columns: 1fr; }
  .is-grid { grid-template-columns: 1fr 1fr; }
  .live-strip { flex-wrap: wrap; }
  .ls-val { font-size: 0.74rem; }
  .cp-actions { gap: 5px; }
  .cp-btn { padding: 8px 12px; font-size: 0.78rem; }
  .cp-config { flex-direction: column; }
  .lab-step { padding: 4px 8px; font-size: 0.66rem; }
}