.tna-wrap{max-width:480px;margin:0 auto;padding:1rem;font-family:system-ui,-apple-system,sans-serif}.tna-problem-card{background:#fff;border:2px solid #e2e8f0;border-radius:20px;padding:1.5rem 1.5rem 1rem;box-shadow:0 4px 16px #00000012;margin-bottom:1.5rem}.tna-col-headers,.tna-carry-row,.tna-num-row,.tna-divider-row,.tna-ans-row{display:grid;grid-template-columns:44px 72px 72px;gap:0 6px;align-items:center;justify-content:center}.tna-col-headers{margin-bottom:4px}.tna-ch{text-align:center;font-size:.72rem;font-weight:700;text-transform:uppercase;letter-spacing:.06em;color:#94a3b8}.tna-sign-cell{text-align:right;padding-right:4px}.tna-digit-cell{display:flex;align-items:center;justify-content:center;height:68px}.tna-ones-shade{background:#f8fafc;border-radius:8px;opacity:.5}.tna-carry-lbl{font-size:.7rem;font-weight:700;color:#f97316;text-transform:uppercase;letter-spacing:.05em;white-space:nowrap}.tna-num-digit{font-size:2.6rem;font-weight:800;color:#1e293b;font-variant-numeric:tabular-nums;font-family:Courier New,monospace}.tna-plus{font-size:2rem;font-weight:800;color:#3b82f6}.tna-divider-row{margin:4px 0}.tna-divider-line{border-top:3px solid #334155;height:0;align-self:center}.tna-box{width:62px;height:62px;border:3px dashed #94a3b8;border-radius:14px;background:#f8fafc;display:flex;align-items:center;justify-content:center;font-size:2.2rem;font-weight:800;font-family:Courier New,monospace;color:#1e293b;cursor:pointer;transition:border-color .15s,background .15s,transform .1s;user-select:none;position:relative}.tna-box:hover{border-color:#3b82f6;background:#eff6ff}.tna-box:active{transform:scale(.95)}.tna-box.tna-filled{border-style:solid;border-color:#3b82f6;background:#eff6ff}.tna-box.tna-correct-box{border-color:#22c55e!important;background:#f0fdf4!important;color:#15803d}.tna-box.tna-wrong-box{border-color:#ef4444!important;background:#fef2f2!important;color:#b91c1c}.tna-carry-box{width:54px;height:54px;font-size:1.8rem;border-color:#f97316;background:#fff7ed}.tna-carry-box.tna-filled{border-color:#f97316;background:#fff7ed}.tna-carry-box:hover{border-color:#ea580c;background:#ffedd5}.tna-instruction{text-align:center;font-size:.9rem;color:#64748b;margin:0 0 .75rem;font-weight:500}.tna-instruction.tna-has-selection{color:#1d4ed8;font-weight:700;font-size:1rem}.tna-digit-pad{display:flex;flex-wrap:wrap;gap:8px;justify-content:center;margin-bottom:1.25rem}.tna-dbt{width:58px;height:58px;border:3px solid #c7d2fe;border-radius:14px;background:linear-gradient(135deg,#e0e7ff,#ddd6fe);font-size:1.6rem;font-weight:800;color:#3730a3;cursor:pointer;transition:all .15s;display:flex;align-items:center;justify-content:center;touch-action:manipulation}.tna-dbt:hover{background:linear-gradient(135deg,#c7d2fe,#c4b5fd);transform:scale(1.07)}.tna-dbt:active{transform:scale(.93)}.tna-dbt.tna-dbt-selected{background:linear-gradient(135deg,#fef08a,#fde047);border-color:#ca8a04;color:#713f12;transform:scale(1.12);box-shadow:0 4px 12px #eab30866}.tna-actions{display:flex;flex-wrap:wrap;gap:8px;justify-content:center;margin-bottom:1.25rem}.tna-btn{padding:.55rem 1.1rem;border:none;border-radius:10px;font-size:.9rem;font-weight:700;cursor:pointer;transition:all .15s;touch-action:manipulation}.tna-btn:hover{filter:brightness(1.08);transform:translateY(-1px)}.tna-btn:active{transform:scale(.96)}.tna-btn-check{background:#22c55e;color:#fff}.tna-btn-new{background:#3b82f6;color:#fff}.tna-btn-hint{background:#f59e0b;color:#fff}.tna-btn-clear{background:#94a3b8;color:#fff}.tna-feedback{padding:1rem 1.25rem;border-radius:14px;font-size:1.05rem;font-weight:600;line-height:1.5;margin-bottom:.75rem;text-align:center}.tna-fb-correct{background:#f0fdf4;border:2px solid #22c55e;color:#15803d}.tna-fb-wrong{background:#fef3c7;border:2px solid #f59e0b;color:#92400e}.tna-fb-missing{background:#fef2f2;border:2px solid #f87171;color:#b91c1c}.tna-hint{background:#eff6ff;border:2px solid #93c5fd;border-radius:14px;padding:1rem 1.25rem;font-size:.95rem;color:#1e40af;line-height:1.7}.tna-hint ol{margin:.4rem 0 0 1.2rem;padding:0}.tna-hint li{margin-bottom:.3rem}.tna-hint strong{color:#1d4ed8}.tna-hidden{display:none!important}@media(max-width:400px){.tna-problem-card{padding:1rem .75rem .75rem}.tna-col-headers,.tna-carry-row,.tna-num-row,.tna-divider-row,.tna-ans-row{grid-template-columns:36px 62px 62px}.tna-num-digit{font-size:2.2rem}.tna-box{width:54px;height:54px;font-size:1.8rem}.tna-carry-box{width:46px;height:46px;font-size:1.5rem}.tna-dbt{width:50px;height:50px;font-size:1.4rem}}*,*:before,*:after{box-sizing:border-box}body{background:linear-gradient(135deg,#fef9ff,#f0f9ff);color:#1c1e21;font-family:system-ui,-apple-system,sans-serif;margin:0;padding:0;min-height:100vh}.page-wrap{max-width:560px;margin:0 auto;padding:1.5rem 1rem 4rem}.topbar{display:flex;align-items:center;gap:.6rem;margin-bottom:1.5rem;flex-wrap:wrap}.topbar a,.topbar button{display:inline-flex;align-items:center;padding:.4rem .9rem;border:1.5px solid #d0d5dd;border-radius:8px;font-size:.88rem;font-weight:600;cursor:pointer;text-decoration:none;background:#fff;color:#374151;transition:background .15s}.topbar a:hover,.topbar button:hover{background:#e9ecef}h1{font-size:1.9rem;font-weight:800;color:#1e293b;margin:0 0 .25rem}.subtitle{color:#64748b;font-size:.95rem;margin:0 0 .5rem}.instructions{color:#374151;font-size:.95rem;line-height:1.6;margin:0 0 1.5rem;padding:.75rem 1rem;background:#fffbeb;border-left:4px solid #f59e0b;border-radius:0 8px 8px 0}