*,:before,:after{box-sizing:border-box}html,body{margin:0;padding:0}*{box-sizing:border-box;-webkit-tap-highlight-color:transparent}body{background:#f0f4f8;justify-content:center;margin:0;font-family:Segoe UI,system-ui,sans-serif;display:flex}.app{flex-direction:column;align-items:center;width:100%;max-width:480px;min-height:100dvh;padding:16px 8px 32px;display:flex}h1{color:#1a2640;letter-spacing:2px;margin:0 0 12px;font-size:1.8rem}.difficulty-bar{gap:8px;margin-bottom:12px;display:flex}.diff-btn{color:#445;cursor:pointer;background:#fff;border:2px solid #c0cfe0;border-radius:20px;padding:6px 14px;font-size:.85rem;font-weight:500;transition:all .15s}.diff-btn.active{color:#fff;background:#2563eb;border-color:#2563eb}.grid{background:#fff;border:3px solid #1a2640;border-radius:4px;grid-template-rows:repeat(9,1fr);grid-template-columns:repeat(9,1fr);width:min(95vw,450px);height:min(95vw,450px);margin-bottom:16px;display:grid}.cell{cursor:pointer;-webkit-user-select:none;user-select:none;border:1px solid #c8d8e8;justify-content:center;align-items:center;font-size:clamp(14px,4vw,22px);font-weight:600;transition:background 80ms;display:flex;position:relative}.cell.box-right{border-right:2.5px solid #1a2640}.cell.box-bottom{border-bottom:2.5px solid #1a2640}.cell.given{color:#1a2640}.cell.user{color:#2563eb}.cell.selected{background:#bfdbfe}.cell.related{background:#e8f0fc}.cell.same-num{background:#dbeafe}.cell.conflict{background:#fee2e2;color:#dc2626!important}.notes-grid{grid-template-rows:repeat(3,1fr);grid-template-columns:repeat(3,1fr);width:100%;height:100%;padding:1px;display:grid}.note{color:#64748b;justify-content:center;align-items:center;font-size:clamp(7px,1.8vw,10px);font-weight:400;line-height:1;display:flex}.numpad{grid-template-columns:repeat(5,1fr);gap:8px;width:min(95vw,450px);margin-bottom:16px;display:grid}.num-btn{aspect-ratio:1;color:#2563eb;cursor:pointer;background:#fff;border:2px solid #c0cfe0;border-radius:10px;justify-content:center;align-items:center;font-size:clamp(18px,5vw,28px);font-weight:700;transition:all .1s;display:flex}.num-btn:active{transform:scale(.92)}.erase-btn{color:#dc2626}.note-btn{color:#64748b;font-size:clamp(16px,4vw,24px)}.note-btn.note-active{color:#2563eb;background:#dbeafe;border-color:#2563eb}.won-banner{color:#166534;background:#dcfce7;border:2px solid #86efac;border-radius:12px;margin-bottom:10px;padding:10px 24px;font-size:1.1rem;font-weight:700}.loading{color:#64748b;margin-top:60px;font-size:1.2rem}.timer{color:#334155;letter-spacing:3px;font-variant-numeric:tabular-nums;margin-bottom:8px;font-size:1.4rem;font-weight:700}.cell.error-cell{animation:.3s flash;color:#b91c1c!important;background:#fecaca!important}@keyframes flash{0%{background:#fca5a5}to{background:#fecaca}}.action-bar{gap:8px;width:min(95vw,450px);margin-top:4px;display:flex}.action-btn{cursor:pointer;color:#334155;background:#fff;border:2px solid #c0cfe0;border-radius:12px;flex:1;padding:11px 4px;font-size:.85rem;font-weight:600;transition:all .12s}.action-btn:active:not(:disabled){transform:scale(.95)}.action-btn:disabled{opacity:.4;cursor:default}.undo-btn:hover:not(:disabled){background:#f1f5f9;border-color:#94a3b8}.check-btn:hover:not(:disabled){color:#92400e;background:#fffbeb;border-color:#fbbf24}.new-btn:hover:not(:disabled){color:#1d4ed8;background:#eff6ff;border-color:#2563eb}.confirm-overlay{z-index:100;background:#00000073;justify-content:center;align-items:center;display:flex;position:fixed;inset:0}.confirm-box{text-align:center;background:#fff;border-radius:16px;width:90%;max-width:320px;padding:24px 20px 16px;box-shadow:0 8px 32px #0003}.confirm-box p{color:#1e293b;margin:0 0 20px;font-size:1rem;line-height:1.5}.confirm-buttons{gap:10px;display:flex}.confirm-yes,.confirm-no{cursor:pointer;border:none;border-radius:10px;flex:1;padding:10px;font-size:.95rem;font-weight:600}.confirm-yes{color:#fff;background:#2563eb}.confirm-yes:hover{background:#1d4ed8}.confirm-no{color:#334155;background:#e2e8f0}.confirm-no:hover{background:#cbd5e1}