:root{font-family:Inter,system-ui,-apple-system,Segoe UI,Roboto,sans-serif;color:#0f172a;background:#f8fafc}*{box-sizing:border-box}body{margin:0}.app-shell{max-width:980px;margin:0 auto;padding:24px}.tabs{display:flex;gap:12px;margin:20px 0}.tabs button.active{background:#1d4ed8;color:#fff}.card{background:#fff;border:1px solid #e2e8f0;border-radius:10px;padding:16px;margin-bottom:16px}label{display:block;margin:12px 0 6px;font-weight:600}input,textarea,select{width:100%;padding:8px;border:1px solid #cbd5e1;border-radius:8px}button{margin-top:12px;border:none;border-radius:8px;background:#2563eb;color:#fff;padding:8px 14px;cursor:pointer}button.secondary{background:#64748b}button.danger{background:#dc2626}.teacher-layout{display:grid;grid-template-columns:1fr 1.2fr;gap:16px}.exercise-list{list-style:none;padding:0}.exercise-list li{display:flex;justify-content:space-between;align-items:center;border-bottom:1px solid #e2e8f0;padding:10px 0}.actions-inline{display:flex;gap:8px}.item-editor{border:1px solid #e2e8f0;border-radius:10px;padding:10px;margin-bottom:12px}.exercise-row{margin:10px 0}.results .correct{border-left:4px solid #16a34a;padding-left:10px;margin-bottom:10px}.results .incorrect{border-left:4px solid #dc2626;padding-left:10px;margin-bottom:10px}.muted{color:#475569}.error{color:#b91c1c}.info{color:#166534}@media (max-width: 860px){.teacher-layout{grid-template-columns:1fr}}