/* Original, scoped arithmetic manipulatives; no motion or external assets. */
.arithmetic-lab{margin:24px 0;padding:clamp(16px,3vw,30px);min-width:0;border:1px solid var(--border-strong);border-radius:24px;background:linear-gradient(140deg,var(--card-grad-1),var(--card))}
.arithmetic-lab h2{margin-top:4px}.arithmetic-lab p{line-height:1.65}.arithmetic-lab [hidden]{display:none!important}
.arithmetic-controls,.arithmetic-navigation{display:flex;flex-wrap:wrap;gap:10px;margin:20px 0}.arithmetic-lab .btn{min-height:44px;white-space:normal;overflow-wrap:anywhere}
.arithmetic-lab .btn[aria-pressed="true"]{border:2px solid var(--brand);background:var(--card-grad-1);color:var(--text)}
.arithmetic-lab button:focus-visible,.arithmetic-lab a:focus-visible{outline:3px solid var(--brand-2);outline-offset:4px}
.arithmetic-lab button:disabled{opacity:.55;cursor:default}.arithmetic-example{padding:18px;min-width:0;border:1px solid var(--border);border-radius:18px;background:var(--card);margin:16px 0}
.arithmetic-steps{list-style:none;padding:0;margin:0}.arithmetic-steps>li{padding:12px 0;border-top:1px solid var(--border)}.arithmetic-steps strong{font-size:1.05rem}
.arithmetic-equation{font-size:clamp(1rem,3vw,1.4rem);font-weight:800;font-variant-numeric:tabular-nums;overflow-wrap:anywhere}
.arithmetic-dots{display:flex;gap:8px;flex-wrap:wrap;max-width:240px;padding:6px 0}.arithmetic-dots>span{display:block;width:20px;height:20px;border:2px solid var(--brand-2);border-radius:50%;background:var(--card-grad-1)}
.arithmetic-ten{display:grid;grid-template-columns:repeat(10,minmax(0,1fr));max-width:240px;width:100%;border:2px solid var(--brand);border-radius:6px;overflow:hidden;background:var(--card-grad-1);margin:8px 0}
.arithmetic-ten>span{height:28px;min-width:0}.arithmetic-ten>span+span{border-left:1px solid var(--brand)}.arithmetic-result{display:flex;align-items:center;gap:12px;flex-wrap:wrap}
.arithmetic-status{padding:12px;border-left:3px solid var(--brand-2);background:var(--card);font-size:.9rem;overflow-wrap:anywhere}.arithmetic-status:empty{display:none}
.arithmetic-credit{font-size:.85rem;color:var(--muted);border-top:1px solid var(--border);padding-top:16px}
@media(max-width:767px){.arithmetic-navigation .btn{flex:1 1 100%}.arithmetic-controls .btn{flex:1 1 60px}.arithmetic-example{padding:12px}.arithmetic-result{display:block}}