.chemistry-opening{margin-bottom:18px}
.lesson-kicker{display:inline-block;color:var(--primary);font-size:11px;font-weight:900;text-transform:uppercase;letter-spacing:.08em;margin-bottom:6px}
.chemistry-story{padding:18px}
.central-question{margin-top:12px!important;padding-top:10px;border-top:1px solid #c9daf4}
.visual-box,.example-box,.experiment-box,.challenge-box,.formula-box,.interactive-lab,.quick-question{border-radius:12px;margin:15px 0}
.visual-box,.example-box{background:var(--surface-soft);border:1px solid var(--line);padding:15px}
.two-col,.comparison-grid{display:grid;grid-template-columns:repeat(2,minmax(0,1fr));gap:12px;margin:14px 0}
.three-col{display:grid;grid-template-columns:repeat(3,minmax(0,1fr));gap:12px;margin:14px 0}
.formula{display:inline-block;background:#f2f6fb;border:1px solid var(--line);border-radius:7px;padding:2px 6px;font-family:Cambria,"Times New Roman",serif}
.formula-box{background:linear-gradient(135deg,#f5f8ff,#fff);border:1px solid #bfd5f5;padding:16px;text-align:center}
.formula-name{display:block;color:var(--primary-dark);font-size:12px;font-weight:900;text-transform:uppercase;letter-spacing:.05em}
.big-formula{font-family:Cambria,"Times New Roman",serif;font-size:30px;font-weight:700;color:var(--primary-dark);margin:8px 0}
.mini-formula{display:block;margin:8px 0;padding:8px 10px;border-radius:8px;background:#f3f7fc;color:var(--primary-dark);font:700 21px/1.2 Cambria,"Times New Roman",serif;text-align:center}
.table-wrap{overflow-x:auto;margin:14px 0}
.table-wrap table{width:100%;border-collapse:collapse}
.table-wrap th,.table-wrap td{border:1px solid var(--line);padding:9px 10px;text-align:left}
.table-wrap th{background:var(--primary-soft);color:var(--primary-dark)}
.lesson-visual{display:block;width:100%;max-width:760px;height:auto;margin:8px auto}
.visual-caption{font-size:13px;color:var(--muted);text-align:center}
.quick-question{border:1px solid var(--line);border-left:5px solid var(--primary);padding:14px;background:#fff}
.quick-question>strong{display:block;color:var(--primary-dark);margin-bottom:4px}
.choice-row{display:flex;gap:8px;flex-wrap:wrap;margin:10px 0}
.choice-row button{border:1px solid #bfd0e7;background:#fff;border-radius:9px;padding:9px 12px;color:var(--text);font-weight:800;cursor:pointer}
.choice-row button:hover{background:var(--primary-soft)}
.choice-row button.is-correct{background:var(--ok-bg);border-color:var(--ok);color:var(--ok)}
.choice-row button.is-wrong{background:var(--danger-bg);border-color:var(--danger);color:var(--danger)}
.choice-feedback{min-height:0;font-size:13px}
.choice-feedback.is-correct{color:var(--ok)}
.choice-feedback.is-wrong{color:var(--danger)}
.equation-walk{display:grid;grid-template-columns:repeat(3,minmax(0,1fr));gap:10px;margin:14px 0}
.equation-walk>div{border:1px solid var(--line);border-radius:11px;padding:13px;background:#fff}
.equation-walk span{display:grid;place-items:center;width:28px;height:28px;border-radius:50%;background:var(--primary);color:#fff;font-weight:900;margin-bottom:7px}
.interactive-lab{border:1px solid #b9d3f6;background:linear-gradient(180deg,#f6faff,#fff);padding:16px}
.lab-heading h4{font-size:18px;color:var(--primary-dark);margin:0 0 12px}
.lab-controls{display:grid;grid-template-columns:repeat(2,minmax(0,1fr));gap:14px}
.lab-controls label{display:grid;gap:7px;font-size:13px;color:var(--muted)}
.lab-controls input,.lab-controls select{width:100%}
.lab-result{display:flex;gap:8px;align-items:center;flex-wrap:wrap;padding:10px 12px;border:1px solid var(--line);border-radius:9px;background:#fff}
.concept-flow{display:grid;grid-template-columns:1fr auto 1fr auto 1fr;align-items:center;gap:8px;margin:16px 0}
.concept-flow>div:not(.flow-arrow){border:1px solid var(--line);border-radius:10px;padding:12px;background:#fff;text-align:center}
.concept-flow strong,.concept-flow span{display:block}
.concept-flow strong{font-size:12px;color:var(--muted)}
.concept-flow span{font-family:Cambria,"Times New Roman",serif;font-size:23px;color:var(--primary-dark);font-weight:700}
.flow-arrow{font-size:22px;font-weight:900;color:var(--primary)}
.reason-steps{margin:10px 0 0 22px;padding:0}
.reason-steps li{margin:8px 0}
.connection-grid{display:grid;grid-template-columns:repeat(4,minmax(0,1fr));gap:10px;margin:14px 0}
.connection-grid>div{border:1px solid var(--line);border-radius:10px;padding:12px;background:#fff}
.connection-grid strong{display:block;color:var(--primary-dark)}
.connection-grid p{font-size:13px;color:var(--muted)}
.experiment-box{background:#f8fbff;border:1px solid var(--line);border-left:5px solid #6d4aff;padding:16px}
.safety-note{margin-top:12px!important;padding-top:10px;border-top:1px dashed #cbd6e5;color:#5b466e}
.chapter-checkpoint{margin-top:28px;padding-top:18px;border-top:2px solid var(--line)}
.challenge-box{background:#f5f2ff;border:1px solid #ddd4ff;border-left:5px solid #6d4aff;padding:15px}
.challenge-box details{margin-top:10px}
.challenge-box summary{cursor:pointer;font-weight:800;color:#5d42bd}
.curriculum-box{margin-top:20px;border:1px dashed #b6c4d4;border-radius:10px;padding:12px 14px;background:#fafcff;color:var(--muted)}
.curriculum-box summary{cursor:pointer;color:var(--primary-dark);font-weight:800}
.analysis-steps{display:grid;grid-template-columns:repeat(5,minmax(0,1fr));gap:9px;margin:15px 0}
.analysis-steps>div{border:1px solid var(--line);border-radius:11px;background:#fff;padding:12px}
.analysis-steps span{display:grid;place-items:center;width:28px;height:28px;border-radius:50%;background:var(--primary);color:#fff;font-size:12px;font-weight:900;margin-bottom:7px}
.analysis-steps strong{display:block;color:var(--primary-dark);margin-bottom:4px}
.analysis-steps p{font-size:13px;color:var(--muted);margin:0}

@media(max-width:1050px){.analysis-steps{grid-template-columns:repeat(3,minmax(0,1fr))}}
@media(max-width:900px){.connection-grid{grid-template-columns:repeat(2,minmax(0,1fr))}}
@media(max-width:720px){
  .two-col,.three-col,.comparison-grid,.equation-walk,.lab-controls,.connection-grid,.analysis-steps{grid-template-columns:1fr}
  .concept-flow{grid-template-columns:1fr}
  .flow-arrow{transform:rotate(90deg);text-align:center}
  .choice-row{display:grid;grid-template-columns:1fr}
  .choice-row button{text-align:left}
  .big-formula{font-size:26px}
  .lesson-visual{min-width:0}
  .chemistry-story{padding:15px}
}