.container-main{max-width:900px;margin:0 auto;padding:var(--spacing-xl) var(--container-padding-x)}.page-title{font-size:var(--font-size-3xl);font-weight:700;color:var(--primary);margin:0;letter-spacing:-.5px}.subtitle{color:var(--text-secondary);font-weight:600;margin-top:var(--spacing-xs);font-size:var(--font-size-sm)}.game-header{display:flex;flex-direction:column;gap:var(--spacing-md);margin-bottom:var(--spacing-lg)}@media(min-width:768px){.game-header{flex-direction:row;justify-content:space-between;align-items:flex-start}}.controls-group{display:flex;flex-direction:column;gap:var(--spacing-sm);width:100%}@media(min-width:640px){.controls-group{flex-direction:row;width:auto;gap:var(--spacing-md)}}.video-link{display:inline-flex;align-items:center;gap:var(--spacing-sm);font-size:var(--font-size-base);font-weight:600;color:var(--primary);text-decoration:none;transition:all var(--transition-normal)}.video-link:hover{color:var(--primary-light)}.difficulty-select{padding:var(--spacing-sm) var(--spacing-md);border-radius:var(--radius-lg);font-weight:600;font-size:var(--font-size-base);border:2px solid var(--outline);background:var(--background);color:var(--text-primary);cursor:pointer;transition:all var(--transition-normal);appearance:none;padding-right:var(--spacing-lg);background-image:url("data:image/svg+xml;charset=UTF-8,%3csvg xmlns='http://www.w3.org/2000/svg' viewBox='0 0 24 24' fill='none' stroke='%23674ea7' stroke-width='2' stroke-linecap='round' stroke-linejoin='round'%3e%3cpolyline points='6 9 12 15 18 9'%3e%3c/polyline%3e%3c/svg%3e");background-repeat:no-repeat;background-position:right var(--spacing-sm) center;background-size:1.5em 1.5em;padding-right:calc(var(--spacing-lg) + .5rem)}.difficulty-select:hover{border-color:var(--primary);background-color:var(--secondary)}.difficulty-select:focus{outline:none;border-color:var(--primary);box-shadow:0 0 0 4px #674ea726}.difficulty-select option{padding:var(--spacing-md);background:var(--background);color:var(--text-primary)}.difficulty-select option:checked{background:linear-gradient(var(--primary),var(--primary));background-color:var(--primary);color:var(--text-on-primary)}.difficulty-option-easy{background:#dcfce7!important;color:#166534!important}.difficulty-option-easy:checked{background:#10b981!important;color:#fff!important}.difficulty-option-medium{background:#fef3c7!important;color:#b45309!important}.difficulty-option-medium:checked{background:#f59e0b!important;color:#fff!important}.difficulty-option-hard{background:#fee2e2!important;color:#991b1b!important}.difficulty-option-hard:checked{background:#ef4444!important;color:#fff!important}.btn-primary{background:var(--primary);color:var(--text-on-primary);padding:var(--spacing-md) var(--spacing-lg);border:none;border-radius:var(--radius-xl);font-weight:700;cursor:pointer;transition:all var(--transition-normal);white-space:nowrap}.btn-primary:hover{background:var(--primary-light);transform:translateY(-2px);box-shadow:0 8px 20px #674ea74d}.btn-primary:active{transform:translateY(0)}.btn-large{padding:var(--spacing-md) var(--spacing-lg);font-size:var(--font-size-sm);width:100%}@media(min-width:640px){.btn-large{width:auto}}.btn-check{padding:var(--spacing-md) var(--spacing-lg);font-size:var(--font-size-base);min-width:200px}.btn-secondary{background:var(--surface);color:var(--text-primary);padding:var(--spacing-md) var(--spacing-lg);border:2px solid var(--outline);border-radius:var(--radius-xl);font-weight:700;font-size:var(--font-size-sm);cursor:pointer;transition:all var(--transition-normal);width:100%}@media(min-width:640px){.btn-secondary{width:auto}}.btn-secondary:hover{background:var(--outline);border-color:var(--primary)}#instructions-feedback{padding:var(--spacing-lg) var(--spacing-xl);border-radius:var(--radius-xl);text-align:center;font-weight:700;font-size:var(--font-size-base);border:2px solid;margin-bottom:var(--spacing-lg);transition:all var(--transition-normal);width:100%;word-wrap:break-word;overflow-wrap:break-word;min-height:60px;display:flex;align-items:center;justify-content:center;background:var(--secondary);color:#6b21a8;border-color:#ddd6fe}#instructions-feedback.instruction-warning,#instructions-feedback.feedback-warning{background:#fef3c7;color:#b45309;border-color:#fcd34d}#instructions-feedback.instruction-success,#instructions-feedback.feedback-success{background:#dcfce7;color:#166534;border-color:#bbf7d0}#instructions-feedback.instruction-info,#instructions-feedback.feedback-info{background:var(--secondary);color:#6b21a8;border-color:#ddd6fe}#instructions-feedback.instruction-hard,#instructions-feedback.feedback-hard{background:#f3e8ff;color:#6b21a8;border-color:#e9d5ff}#instructions-feedback.feedback-error{background:#fee2e2;color:#991b1b;border-color:#fecaca}.game-area{margin-bottom:var(--spacing-lg)}.game-container{display:flex;justify-content:center;align-items:center;padding:var(--spacing-lg) 0;gap:var(--spacing-lg);position:relative}.plus-symbol{font-size:3.5rem;color:#cbd5e1;font-weight:700;display:none}@media(min-width:768px){.plus-symbol{display:block;position:absolute;left:-40px}}.math-grid{display:flex;flex-direction:row-reverse;gap:2px;justify-content:center;flex-wrap:wrap;font-family:Arial,Calibri,Trebuchet MS,sans-serif}.math-font{font-family:Arial,Calibri,Trebuchet MS,sans-serif}.digit-column{display:flex;flex-direction:column;align-items:center;width:90px;position:relative}.blank-column{width:90px;display:flex;flex-direction:column;align-items:center;padding-top:212px}.blank-space{height:4rem;width:100%}.carry-display{height:30px;font-size:1.5rem;color:var(--error);font-weight:700;display:flex;align-items:center;justify-content:center;margin-bottom:var(--spacing-xs);transition:all var(--transition-normal);min-height:30px}.carry-active{animation:popIn .3s ease-out}.digit-main{font-size:4rem;margin-bottom:var(--spacing-xs);color:var(--text-primary);font-weight:700;transition:all var(--transition-normal);line-height:1}.digit-sub{font-size:4rem;margin-bottom:var(--spacing-sm);color:var(--text-primary);font-weight:700;line-height:1}.digit-line{width:100%;height:3px;background:var(--text-primary);border-radius:2px;margin-bottom:var(--spacing-sm)}.input-result{width:80px;height:90px;text-align:center;font-size:2.5rem;border:3px solid var(--outline);border-radius:var(--radius-lg);background:var(--background);transition:all var(--transition-normal);margin-top:var(--spacing-xs);font-family:Arial,Calibri,Trebuchet MS,sans-serif;font-weight:700;color:var(--text-primary);line-height:1}.input-result::-webkit-outer-spin-button,.input-result::-webkit-inner-spin-button{-webkit-appearance:none;margin:0}.input-result:focus{outline:none;border-color:var(--primary);background:var(--secondary);box-shadow:0 0 0 4px #674ea726}.input-wrapper{display:flex;flex-direction:column;align-items:center;gap:var(--spacing-xs);margin-top:var(--spacing-sm)}.input-sum{width:70px;height:50px;text-align:center;font-size:1.5rem;border:3px solid #bfdbfe;border-radius:var(--radius-lg);background:#dbeafe;transition:all var(--transition-normal);font-family:Arial,Calibri,Trebuchet MS,sans-serif;font-weight:700;color:var(--text-primary);line-height:1}.input-sum::-webkit-outer-spin-button,.input-sum::-webkit-inner-spin-button{-webkit-appearance:none;margin:0}.input-sum:focus{outline:none;border-color:var(--primary);background:var(--secondary);box-shadow:0 0 0 4px #674ea726}.input-sum-disabled{width:70px;height:50px;text-align:center;font-size:1.5rem;border:3px solid #bfdbfe;border-radius:var(--radius-lg);background:#e5eef9;font-family:Arial,Calibri,Trebuchet MS,sans-serif;font-weight:700;color:var(--text-primary);line-height:1;cursor:not-allowed;opacity:.7}.input-sum-disabled::-webkit-outer-spin-button,.input-sum-disabled::-webkit-inner-spin-button{-webkit-appearance:none;margin:0}.input-final{width:70px;height:50px;text-align:center;font-size:1.5rem;border:3px solid #bfdbfe;border-radius:var(--radius-lg);background:#dbeafe;transition:all var(--transition-normal);font-family:Arial,Calibri,Trebuchet MS,sans-serif;font-weight:700;color:var(--text-primary);line-height:1}.input-final::-webkit-outer-spin-button,.input-final::-webkit-inner-spin-button{-webkit-appearance:none;margin:0}.input-final:focus{outline:none;border-color:var(--primary);background:var(--secondary);box-shadow:0 0 0 4px #674ea726}.correct-answer{font-size:1rem;color:#10b981;font-weight:700;text-align:center;margin-top:var(--spacing-xs);min-height:1.5rem;transition:all var(--transition-normal)}.hard-input-wrapper{display:flex;flex-direction:column;align-items:center;gap:var(--spacing-xs)}.input-label{font-size:.65rem;font-weight:700;color:var(--text-secondary);text-transform:uppercase}.hint-text{font-size:.65rem;color:var(--error);font-weight:700;margin-top:var(--spacing-xs);height:16px;transition:all var(--transition-normal);opacity:0}.hint-visible{opacity:1}.hint-correct{color:#10b981}.hint-error{color:var(--error)}.button-group{display:flex;flex-direction:column;gap:var(--spacing-sm);justify-content:center;align-items:center;margin-top:var(--spacing-lg)}@media(min-width:640px){.button-group{flex-direction:row;gap:var(--spacing-md)}}.hidden{display:none}.hard-mode-display{text-align:center;font-size:2rem;margin:var(--spacing-lg) 0}.hard-number{margin-bottom:var(--spacing-md);font-size:4rem;font-weight:700;color:var(--text-primary);line-height:1.2}.hard-operator{font-size:3rem;font-weight:700;color:#cbd5e1;margin-bottom:var(--spacing-md)}.hard-divider{border-top:4px solid var(--text-primary);padding-top:var(--spacing-md);margin:var(--spacing-md) 0}.hard-inputs{display:flex;flex-direction:row-reverse;gap:var(--spacing-md);justify-content:center;flex-wrap:wrap;margin-top:var(--spacing-lg)}@keyframes popIn{0%{transform:scale(0);opacity:0}50%{transform:scale(1.2)}to{transform:scale(1);opacity:1}}