.proof-builder{margin:22px auto;padding:20px;max-width:980px;border:1px solid var(--line,#dbe4de);border-radius:16px;background:var(--surface,#fff)}.proof-builder h2{margin:0 0 6px}.proof-builder>p{margin:0 0 16px}.proof-exercise-controls{display:flex;align-items:end;gap:10px;margin:14px 0}.proof-exercise-controls label{flex:1}.proof-builder label{display:grid;gap:6px;font-weight:750}.proof-builder input,.proof-builder select{width:100%;min-height:44px;padding:9px 11px;border:1px solid var(--line,#cbd5e1);border-radius:9px;background:#fff;color:var(--ink,#0f172a);font:inherit}.proof-problem{display:grid;grid-template-columns:1fr 1fr;gap:12px;margin:14px 0}.proof-problem>div{padding:12px 14px;border-left:3px solid var(--brand,var(--primary,#2563eb));background:var(--brand-soft,#eff6ff)}.proof-problem small{font-size:.72rem;font-weight:850;letter-spacing:.08em;color:var(--muted,#475569)}.proof-problem p{margin:5px 0 0;font-weight:750}.proof-table{width:100%;margin:14px 0;border-collapse:collapse}.proof-table th,.proof-table td{padding:9px;text-align:left;border-bottom:1px solid var(--line,#e2e8f0);vertical-align:top}.proof-table th{font-size:.84rem;color:var(--muted,#475569)}.proof-table input,.proof-table select{min-height:42px}.proof-actions{display:flex;gap:10px;flex-wrap:wrap}@media(max-width:640px){.proof-builder{padding:15px}.proof-exercise-controls{display:grid;grid-template-columns:1fr 1fr}.proof-exercise-controls label{grid-column:1/-1}.proof-problem{grid-template-columns:1fr}.proof-table th,.proof-table td{padding:7px 4px;font-size:.88rem}}