.sub-app:where(.astro-6fl3e4ty){max-width:480px;margin:0 auto}.score-bar:where(.astro-6fl3e4ty){display:flex;justify-content:space-between;align-items:center;background:#edf2f7;border-radius:12px;padding:.7rem 1.2rem;margin-bottom:1.5rem;font-size:1rem;font-weight:600;color:#4a5568}.q-correct:where(.astro-6fl3e4ty){color:#38a169}.problem-card:where(.astro-6fl3e4ty){background:#fff;border:3px solid #e2e8f0;border-radius:20px;padding:1.5rem 2rem 1.8rem;display:flex;flex-direction:column;align-items:flex-start;gap:0;box-shadow:0 4px 16px #667eea1f}.prob-row:where(.astro-6fl3e4ty){display:flex;flex-direction:row;align-items:center;gap:8px;width:100%}.cell-op:where(.astro-6fl3e4ty){width:52px;display:flex;align-items:center;justify-content:flex-end;flex-shrink:0}.cell-tens:where(.astro-6fl3e4ty),.cell-ones:where(.astro-6fl3e4ty){width:84px;height:72px;display:flex;align-items:center;justify-content:center;flex-shrink:0}.prob-digit:where(.astro-6fl3e4ty){font-size:3rem;font-weight:900;color:#1a202c;font-family:Courier New,monospace;line-height:1}.op-minus:where(.astro-6fl3e4ty){font-size:2.8rem;font-weight:900;color:#e53e3e;justify-content:flex-end;padding-right:2px}.divider-row:where(.astro-6fl3e4ty){width:100%;padding:5px 0}.divider-line:where(.astro-6fl3e4ty){width:236px;height:4px;background:#2d3748;border-radius:2px}.borrow-row:where(.astro-6fl3e4ty){padding-bottom:6px;min-height:64px}.borrow-label-left:where(.astro-6fl3e4ty){font-size:.72rem;color:#a0aec0;text-align:right;line-height:1.3;white-space:nowrap}.borrow-tens-cell:where(.astro-6fl3e4ty){height:60px;justify-content:center}.borrow-ones-cell:where(.astro-6fl3e4ty){height:60px;justify-content:center;flex-direction:row;gap:6px}.minus-one-badge:where(.astro-6fl3e4ty){font-size:1.15rem;font-weight:800;color:#cbd5e0;background:#f7fafc;padding:4px 8px;border-radius:8px;border:2px solid #e2e8f0;transition:all .3s ease;display:inline-block}.minus-one-badge:where(.astro-6fl3e4ty).active{color:#e53e3e;background:#fff5f5;border-color:#feb2b2}.input-box:where(.astro-6fl3e4ty){border:3px dashed #667eea;border-radius:12px;display:flex;align-items:center;justify-content:center;cursor:pointer;background:#f0f4ff;transition:all .2s ease;user-select:none;touch-action:manipulation;-webkit-tap-highlight-color:transparent}.borrow-input:where(.astro-6fl3e4ty){width:52px;height:52px}.ans-input:where(.astro-6fl3e4ty){width:72px;height:72px}.box-val:where(.astro-6fl3e4ty){font-size:2.2rem;font-weight:900;color:#4c51bf;line-height:1;pointer-events:none}.borrow-input:where(.astro-6fl3e4ty) .box-val:where(.astro-6fl3e4ty){font-size:1.8rem}.input-box:where(.astro-6fl3e4ty):hover,.input-box:where(.astro-6fl3e4ty).drag-over{border-color:#764ba2;background:#e9d8fd;transform:scale(1.06)}.input-box:where(.astro-6fl3e4ty).filled{border-style:solid;border-color:#667eea;background:#fff}.input-box:where(.astro-6fl3e4ty).selected-target{border-color:#d69e2e;background:#fefcbf;border-style:solid;animation:pulse-target .6s ease infinite alternate}.input-box:where(.astro-6fl3e4ty).correct-box{border-color:#38a169!important;background:#f0fff4!important;border-style:solid!important}.input-box:where(.astro-6fl3e4ty).wrong-box{border-color:#e53e3e!important;background:#fff5f5!important;border-style:solid!important;animation:shake .4s ease}@keyframes pulse-target{0%{box-shadow:0 0 0 2px #d69e2e4d}to{box-shadow:0 0 0 6px #d69e2e00}}@keyframes shake{0%,to{transform:translate(0)}25%{transform:translate(-4px)}75%{transform:translate(4px)}}.clear-btn:where(.astro-6fl3e4ty){background:#fc8181;color:#fff;border:none;border-radius:50%;width:22px;height:22px;font-size:.8rem;cursor:pointer;display:flex;align-items:center;justify-content:center;padding:0;flex-shrink:0;transition:background .2s,transform .15s;touch-action:manipulation;-webkit-tap-highlight-color:transparent}.clear-btn:where(.astro-6fl3e4ty):hover{background:#e53e3e;transform:scale(1.15)}.ans-cell:where(.astro-6fl3e4ty){flex-direction:column!important;gap:6px!important;height:auto!important}.col-labels-row:where(.astro-6fl3e4ty){display:flex;gap:8px;margin-top:6px;padding-left:0}.col-label-op:where(.astro-6fl3e4ty){width:52px;flex-shrink:0}.col-label:where(.astro-6fl3e4ty){width:84px;text-align:center;font-size:.8rem;color:#718096;font-weight:700;text-transform:uppercase;letter-spacing:.06em;flex-shrink:0}.digit-pad-section:where(.astro-6fl3e4ty){margin:1.5rem 0 0}.digit-pad-hint:where(.astro-6fl3e4ty){text-align:center;color:#718096;font-size:.95rem;margin:0 0 .8rem;font-weight:500;min-height:1.4em;transition:color .3s}.digit-pad-hint:where(.astro-6fl3e4ty).digit-selected{color:#667eea;font-weight:700}.digit-buttons:where(.astro-6fl3e4ty){display:grid;grid-template-columns:repeat(5,1fr);gap:10px;max-width:360px;margin:0 auto}.digit-btn:where(.astro-6fl3e4ty){width:100%;aspect-ratio:1;border-radius:50%;border:3px solid #667eea;background:#fff;font-size:1.7rem;font-weight:900;color:#667eea;cursor:pointer;transition:all .18s ease;display:flex;align-items:center;justify-content:center;user-select:none;touch-action:manipulation;-webkit-tap-highlight-color:transparent;font-family:Courier New,monospace}.digit-btn:where(.astro-6fl3e4ty):hover{background:#ebf4ff;transform:scale(1.08)}.digit-btn:where(.astro-6fl3e4ty):active{transform:scale(.95)}.digit-btn:where(.astro-6fl3e4ty).selected{background:#667eea;color:#fff;border-color:#4c51bf;transform:scale(1.12);box-shadow:0 4px 14px #667eea80}.action-row:where(.astro-6fl3e4ty){display:flex;gap:.8rem;justify-content:center;flex-wrap:wrap;margin:1.5rem 0}.action-btn:where(.astro-6fl3e4ty){padding:.9rem 1.4rem;border:none;border-radius:50px;font-size:1rem;font-weight:700;cursor:pointer;transition:all .25s ease;box-shadow:0 4px 12px #00000026;touch-action:manipulation;-webkit-tap-highlight-color:transparent;white-space:nowrap}.check-btn:where(.astro-6fl3e4ty){background:linear-gradient(135deg,#38a169,#276749);color:#fff}.hint-btn:where(.astro-6fl3e4ty){background:linear-gradient(135deg,#ed8936,#c05621);color:#fff}.new-btn:where(.astro-6fl3e4ty){background:linear-gradient(135deg,#667eea,#764ba2);color:#fff}.action-btn:where(.astro-6fl3e4ty):hover{transform:translateY(-2px);box-shadow:0 6px 18px #00000038}.action-btn:where(.astro-6fl3e4ty):active{transform:translateY(0)}.feedback-box:where(.astro-6fl3e4ty){padding:1rem 1.3rem;border-radius:14px;font-size:1.05rem;font-weight:600;text-align:center;margin-top:.5rem;line-height:1.5;animation:fadeIn .3s ease}.feedback-box:where(.astro-6fl3e4ty).correct{background:#f0fff4;color:#276749;border:2px solid #9ae6b4}.feedback-box:where(.astro-6fl3e4ty).incorrect{background:#fff5f5;color:#742a2a;border:2px solid #feb2b2}.hint-area:where(.astro-6fl3e4ty){background:ivory;color:#744210;border:2px solid #f6e05e;border-radius:14px;padding:1rem 1.3rem;font-size:1rem;line-height:1.7;margin-top:.8rem;animation:fadeIn .3s ease}@keyframes fadeIn{0%{opacity:0;transform:translateY(4px)}to{opacity:1;transform:translateY(0)}}@media(max-width:400px){.problem-card:where(.astro-6fl3e4ty){padding:1rem 1.2rem 1.4rem}.cell-tens:where(.astro-6fl3e4ty),.cell-ones:where(.astro-6fl3e4ty){width:72px;height:64px}.prob-digit:where(.astro-6fl3e4ty){font-size:2.6rem}.ans-input:where(.astro-6fl3e4ty){width:62px;height:62px}.box-val:where(.astro-6fl3e4ty){font-size:2rem}.divider-line:where(.astro-6fl3e4ty){width:204px}.col-label:where(.astro-6fl3e4ty){width:72px}.action-btn:where(.astro-6fl3e4ty){font-size:.9rem;padding:.8rem 1.1rem}}*{box-sizing:border-box}body{background:linear-gradient(135deg,#667eea,#764ba2);color:#fff;font-family:Arial,sans-serif;margin:0;padding:0;min-height:100vh}main{padding:1.5rem 1rem;max-width:640px;margin:0 auto}.page-container{background:#fffffffa;border-radius:24px;padding:2rem 1.8rem;box-shadow:0 12px 40px #0000004d;color:#333}.nav-links{display:flex;gap:1rem;justify-content:center;margin-bottom:1.5rem;flex-wrap:wrap}.nav-btn{display:inline-flex;align-items:center;gap:.45rem;padding:.7rem 1.4rem;border:2px solid #dee2e6;border-radius:50px;font-size:.95rem;font-weight:600;cursor:pointer;transition:all .25s ease;text-decoration:none;background:#fff;color:#495057;box-shadow:0 2px 8px #00000014}.nav-btn:hover{transform:translateY(-2px);box-shadow:0 4px 14px #00000024}.back-btn:hover{background:#667eea;color:#fff;border-color:#667eea}.home-btn:hover{background:#764ba2;color:#fff;border-color:#764ba2}.page-title{color:#667eea;text-align:center;font-size:2.4rem;font-weight:900;margin:0 0 .3rem;text-shadow:1px 2px 4px rgba(102,126,234,.15)}.page-subtitle{text-align:center;color:#718096;font-size:1rem;margin:0 0 .6rem;font-style:italic}.page-instructions{text-align:center;color:#4a5568;font-size:1.05rem;line-height:1.7;margin:0 0 1.5rem}.how-to-card{background:#f7fafc;border:2px solid #e2e8f0;border-radius:16px;padding:1.2rem 1.5rem;margin-bottom:1.8rem}.how-to-title{font-size:1.15rem;font-weight:800;color:#667eea;margin:0 0 1rem}.how-to-steps{display:flex;flex-direction:column;gap:.6rem;margin-bottom:1rem}.step{display:flex;align-items:flex-start;gap:.8rem;font-size:.95rem;color:#4a5568;line-height:1.5}.step-num{background:#667eea;color:#fff;border-radius:50%;width:24px;height:24px;font-size:.8rem;font-weight:800;display:flex;align-items:center;justify-content:center;flex-shrink:0;margin-top:1px}.example-block{background:#fff;border:2px solid #bee3f8;border-radius:10px;padding:.8rem 1rem;display:flex;flex-wrap:wrap;align-items:center;gap:.6rem;font-size:.9rem;color:#2d3748}.example-label{font-weight:700;color:#2b6cb0}.example-code{background:#ebf8ff;color:#2c5282;padding:.3rem .7rem;border-radius:8px;font-family:Courier New,monospace;font-size:1rem;font-weight:700;border:1px solid #bee3f8}.example-detail{color:#4a5568;line-height:1.6}.worksheet-wrapper{background:#f7faff;border:2px solid #e2e8f0;border-radius:20px;padding:1.5rem 1.2rem}@media(max-width:480px){main{padding:.8rem .5rem}.page-container{padding:1.3rem 1rem;border-radius:16px}.page-title{font-size:1.9rem}.how-to-card{padding:1rem}.worksheet-wrapper{padding:1rem .7rem}}