*{box-sizing:border-box;margin:0;padding:0}body{font-family:-apple-system,BlinkMacSystemFont,Segoe UI,system-ui,sans-serif;background:#f5f5f7;color:#1d1d1f;line-height:1.5;padding:2rem}#app{max-width:800px;margin:0 auto}header h1{font-size:1.6rem;font-weight:700;margin-bottom:.25rem;color:#6b21a8}.header-note{font-size:.85rem;color:#666;margin-bottom:1.5rem}.header-note a{color:#6b21a8;text-decoration:none}.header-note a:hover{text-decoration:underline}.level-buttons{display:flex;flex-wrap:wrap;gap:.4rem;margin-bottom:.5rem}.level-buttons button{min-width:2.5rem;padding:.4rem .7rem;border:2px solid #6b21a8;border-radius:8px;background:#fff;color:#6b21a8;font-weight:600;font-size:.85rem;cursor:pointer;transition:background .15s,color .15s}.level-buttons button:hover{background:#f3e8ff}.level-buttons button.active{background:#6b21a8;color:#fff}.var-buttons{display:inline-flex;gap:.3rem}.var-buttons button{padding:.3rem .6rem;border:2px solid #6b21a8;border-radius:6px;background:#fff;color:#6b21a8;font-weight:600;font-size:.9rem;cursor:pointer;min-width:2rem;transition:background .15s,color .15s}.var-buttons button:hover{background:#f3e8ff}.var-buttons button.active{background:#6b21a8;color:#fff}.emoji-inputs{display:inline-flex;align-items:center;gap:.3rem}.emoji-input{width:2.5rem;text-align:center;font-size:1rem;padding:.2rem;border:1px solid #ccc;border-radius:4px}.level-set-row{display:flex;align-items:center;gap:.5rem;margin-bottom:.6rem}.level-set-description{font-size:.8rem;color:#888;font-style:italic}.level-description{font-size:.85rem;color:#666;min-height:1.2em}section{background:#fff;border-radius:12px;padding:1.25rem 1.5rem;margin-bottom:1rem;box-shadow:0 1px 3px #00000014}h2{font-size:.85rem;text-transform:uppercase;letter-spacing:.05em;color:#86868b;margin-bottom:.75rem}h3{font-size:.8rem;color:#999;margin-bottom:.4rem}.equation-list{display:flex;flex-direction:column;gap:.25rem}.eq-row{display:flex;align-items:center;gap:.75rem;padding:.5rem .75rem;border-radius:8px;cursor:pointer;transition:background .12s}.eq-row:hover{background:#f5f0fa}.eq-row.active{background:#ede5f7;box-shadow:inset 3px 0 #6b21a8}.eq-number{font-size:.7rem;font-weight:700;color:#fff;background:#6b21a8;width:1.5em;height:1.5em;border-radius:50%;display:flex;align-items:center;justify-content:center;flex-shrink:0}.eq-row.active .eq-number{background:#4a1571}.eq-text{font-size:1.6rem;font-weight:700;color:#4a1d7a;font-family:Georgia,serif;letter-spacing:.02em}.claim-btn{background:#6b21a8;color:#fff;border:none;border-radius:6px;padding:.4rem .8rem;font-weight:600;font-size:.85rem;cursor:pointer;transition:background .15s}.claim-btn:hover{background:#581c87}.claim-result{font-weight:600;font-size:.9rem;margin-left:.5rem}.claim-result.correct{color:#16a34a}.claim-result.incorrect{color:#dc2626}.eq-solved{margin-left:auto;font-size:1.4rem;color:#16a34a;font-weight:700}.active-label{font-size:.75rem;font-weight:400;color:#86868b}.hint{font-size:.78rem;color:#86868b;margin-bottom:.5rem}.hint code{background:#f0f0f2;padding:.1rem .3rem;border-radius:3px;font-size:.75rem}.substitute-bar{display:flex;align-items:center;gap:.6rem;margin-top:.5rem;padding:.5rem .75rem;background:#ecfdf5;border-radius:8px;border:1px solid #a7f3d0}.substitute-bar span{font-size:.82rem;color:#047857}#substitute-btn{background:#059669;font-size:.8rem;padding:.3rem .7rem}#substitute-btn:hover{background:#047857}.equation-render{font-size:2.2rem;font-weight:700;color:#4a1d7a;text-align:center;padding:.75rem 0;font-family:Georgia,serif;letter-spacing:.02em}.annotated-render{display:flex;justify-content:center;gap:.3rem;flex-wrap:wrap;padding-bottom:.5rem}.ann-term{display:flex;flex-direction:column;align-items:center}.ann-term .value{font-size:1.5rem;font-weight:700;color:#4a1d7a;font-family:Georgia,serif}.ann-term .label{font-size:.6rem;text-transform:uppercase;letter-spacing:.06em;color:#d946a8;font-weight:600;margin-top:2px}.ann-operator .value{color:#4a1d7a;padding:0 .15rem}.ann-equals .value{color:#4a1d7a;padding:0 .4rem}.ann-bracket{display:flex;align-items:center;gap:.2rem}.ann-bracket-bar{border-bottom:2px solid #d946a8;padding-bottom:2px}.ann-bracket .bracket-label{font-size:.55rem;text-transform:uppercase;letter-spacing:.06em;color:#d946a8;font-weight:600}.gen-controls{display:flex;flex-direction:column;gap:.6rem}.gen-row{display:flex;gap:.6rem;align-items:center;flex-wrap:wrap}.gen-row label{font-size:.8rem;color:#666}.checkbox-label{display:flex;align-items:center;gap:.25rem;font-size:.8rem;color:#444;cursor:pointer;-webkit-user-select:none;user-select:none}.checkbox-label input[type=checkbox]{accent-color:#6b21a8}.solution-badge{font-size:.8rem;color:#16a34a;font-weight:600;font-family:Georgia,serif}#generate-btn{background:#059669}#generate-btn:hover{background:#047857}.input-row{display:flex;gap:.5rem;align-items:center}input[type=text],input[type=number],select{padding:.4rem .6rem;border:1px solid #d1d1d6;border-radius:6px;font-size:.9rem;outline:none;transition:border-color .15s}input[type=text]:focus,input[type=number]:focus,select:focus{border-color:#6b21a8}input[type=text]{flex:1}input.narrow{width:3rem}button{padding:.4rem .9rem;background:#6b21a8;color:#fff;border:none;border-radius:6px;font-size:.85rem;font-weight:500;cursor:pointer;transition:background .15s;white-space:nowrap}button:hover{background:#581c87}button:active{background:#4a1571}.op-group{margin-bottom:.75rem;padding-bottom:.75rem;border-bottom:1px solid #f0f0f2}.op-group:last-child{border-bottom:none;margin-bottom:0;padding-bottom:0}.op-row{display:flex;gap:.4rem;align-items:center;flex-wrap:wrap}.op-row label{font-size:.8rem;color:#666}.error{color:#dc2626;font-size:.85rem;margin-top:.4rem;min-height:1.2em}.result{font-size:.85rem;margin-top:.4rem;min-height:1.2em}.result.success{color:#16a34a}.result.failure{color:#dc2626}#step-list{list-style:none;counter-reset:step}#step-list li{counter-increment:step;padding:.4rem 0;border-bottom:1px solid #f0f0f2;display:flex;gap:.75rem;align-items:baseline}#step-list li:last-child{border-bottom:none}#step-list li:before{content:counter(step);font-size:.7rem;font-weight:700;color:#fff;background:#6b21a8;width:1.4em;height:1.4em;border-radius:50%;display:flex;align-items:center;justify-content:center;flex-shrink:0}.step-op{font-size:.8rem;color:#86868b;min-width:12rem}.step-eq{font-size:1rem;font-weight:600;color:#4a1d7a;font-family:Georgia,serif}