:root{--color-primary: #2563eb;--color-primary-dark: #1d4ed8;--color-primary-light: #3b82f6;--color-background: #ffffff;--color-background-secondary: #f8fafc;--color-surface: #ffffff;--color-text-primary: #1e293b;--color-text-secondary: #64748b;--color-text-muted: #94a3b8;--color-border: #e2e8f0;--color-border-light: #f1f5f9;--color-grade-1: #ef4444;--color-grade-1-dark: #dc2626;--color-grade-2: #f59e0b;--color-grade-2-dark: #d97706;--color-grade-3: #84cc16;--color-grade-3-dark: #65a30d;--color-grade-4: #22c55e;--color-grade-4-dark: #16a34a;--color-success: #22c55e;--color-warning: #f59e0b;--color-error: #ef4444;--color-streak: #f97316;--space-xs: .25rem;--space-sm: .5rem;--space-md: 1rem;--space-lg: 1.5rem;--space-xl: 2rem;--space-2xl: 3rem;--font-family: system-ui, -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, sans-serif;--font-size-xs: .75rem;--font-size-sm: .875rem;--font-size-base: 1rem;--font-size-lg: 1.125rem;--font-size-xl: 1.25rem;--font-size-2xl: 1.5rem;--font-size-3xl: 1.875rem;--font-weight-normal: 400;--font-weight-medium: 500;--font-weight-semibold: 600;--font-weight-bold: 700;--line-height-tight: 1.25;--line-height-normal: 1.5;--line-height-relaxed: 1.75;--radius-sm: .375rem;--radius-md: .5rem;--radius-lg: .75rem;--radius-xl: 1rem;--radius-full: 9999px;--shadow-sm: 0 1px 2px 0 rgb(0 0 0 / .05);--shadow-md: 0 4px 6px -1px rgb(0 0 0 / .1), 0 2px 4px -2px rgb(0 0 0 / .1);--shadow-lg: 0 10px 15px -3px rgb(0 0 0 / .1), 0 4px 6px -4px rgb(0 0 0 / .1);--transition-fast: .15s ease;--transition-normal: .2s ease;--transition-slow: .3s ease;--tap-target-min: 44px;--button-height: 48px;--button-height-lg: 56px}@media(prefers-color-scheme:dark){:root{--color-background: #0f172a;--color-background-secondary: #1e293b;--color-surface: #1e293b;--color-text-primary: #f1f5f9;--color-text-secondary: #94a3b8;--color-text-muted: #64748b;--color-border: #334155;--color-border-light: #1e293b}}*,*:before,*:after{box-sizing:border-box;margin:0;padding:0}html{font-size:16px;-webkit-text-size-adjust:100%;-webkit-tap-highlight-color:transparent}body{font-family:var(--font-family);font-size:var(--font-size-base);line-height:var(--line-height-normal);color:var(--color-text-primary);background-color:var(--color-background);min-height:100vh;min-height:100dvh}h1,h2,h3,h4,h5,h6{font-weight:var(--font-weight-semibold);line-height:var(--line-height-tight)}h1{font-size:var(--font-size-3xl)}h2{font-size:var(--font-size-2xl)}h3{font-size:var(--font-size-xl)}h4{font-size:var(--font-size-lg)}p{margin-bottom:var(--space-md)}a{color:var(--color-primary);text-decoration:none}a:hover{text-decoration:underline}.btn{display:inline-flex;align-items:center;justify-content:center;gap:var(--space-sm);min-height:var(--button-height);padding:var(--space-sm) var(--space-lg);font-family:inherit;font-size:var(--font-size-base);font-weight:var(--font-weight-medium);line-height:1;text-align:center;text-decoration:none;border:none;border-radius:var(--radius-lg);cursor:pointer;transition:all var(--transition-fast);-webkit-appearance:none;-moz-appearance:none;appearance:none;-webkit-user-select:none;user-select:none;touch-action:manipulation}.btn:active{transform:scale(.98)}.btn:disabled{opacity:.5;cursor:not-allowed;transform:none}.btn-primary{background-color:var(--color-primary);color:#fff}.btn-primary:hover:not(:disabled){background-color:var(--color-primary-dark)}.btn-secondary{background-color:var(--color-background-secondary);color:var(--color-text-primary);border:1px solid var(--color-border)}.btn-secondary:hover:not(:disabled){background-color:var(--color-border-light)}.btn-lg{min-height:var(--button-height-lg);font-size:var(--font-size-lg);padding:var(--space-md) var(--space-xl)}.btn-block{width:100%}.card{background-color:var(--color-surface);border:1px solid var(--color-border);border-radius:var(--radius-lg);padding:var(--space-lg);box-shadow:var(--shadow-sm)}.card-clickable{cursor:pointer;transition:all var(--transition-fast)}.card-clickable:hover{box-shadow:var(--shadow-md);border-color:var(--color-primary-light)}.card-clickable:active{transform:scale(.99)}.input{width:100%;min-height:var(--button-height);padding:var(--space-sm) var(--space-md);font-family:inherit;font-size:var(--font-size-base);color:var(--color-text-primary);background-color:var(--color-surface);border:1px solid var(--color-border);border-radius:var(--radius-md);transition:border-color var(--transition-fast);-webkit-appearance:none;-moz-appearance:none;appearance:none}.input:focus{outline:none;border-color:var(--color-primary);box-shadow:0 0 0 3px #2563eb1a}.input::placeholder{color:var(--color-text-muted)}.label{display:block;margin-bottom:var(--space-xs);font-size:var(--font-size-sm);font-weight:var(--font-weight-medium);color:var(--color-text-secondary)}.container{width:100%;max-width:640px;margin:0 auto;padding:0 var(--space-md)}.page{min-height:100vh;min-height:100dvh;display:flex;flex-direction:column}.page-content{flex:1;padding:var(--space-lg) 0}.stack{display:flex;flex-direction:column}.stack-sm{gap:var(--space-sm)}.stack-md{gap:var(--space-md)}.stack-lg{gap:var(--space-lg)}.stack-xl{gap:var(--space-xl)}.row{display:flex;flex-direction:row;align-items:center}.row-between{justify-content:space-between}.row-center{justify-content:center}.text-center{text-align:center}.text-left{text-align:left}.text-right{text-align:right}.text-sm{font-size:var(--font-size-sm)}.text-lg{font-size:var(--font-size-lg)}.text-xl{font-size:var(--font-size-xl)}.text-2xl{font-size:var(--font-size-2xl)}.text-muted{color:var(--color-text-muted)}.text-secondary{color:var(--color-text-secondary)}.text-primary{color:var(--color-primary)}.text-success{color:var(--color-success)}.text-warning{color:var(--color-warning)}.text-error{color:var(--color-error)}.font-medium{font-weight:var(--font-weight-medium)}.font-semibold{font-weight:var(--font-weight-semibold)}.font-bold{font-weight:var(--font-weight-bold)}.mt-sm{margin-top:var(--space-sm)}.mt-md{margin-top:var(--space-md)}.mt-lg{margin-top:var(--space-lg)}.mt-xl{margin-top:var(--space-xl)}.mb-sm{margin-bottom:var(--space-sm)}.mb-md{margin-bottom:var(--space-md)}.mb-lg{margin-bottom:var(--space-lg)}.mb-xl{margin-bottom:var(--space-xl)}.p-md{padding:var(--space-md)}.p-lg{padding:var(--space-lg)}.grade-buttons{display:grid;grid-template-columns:repeat(4,1fr);gap:var(--space-sm);padding:var(--space-md);background-color:var(--color-background-secondary);border-top:1px solid var(--color-border)}.grade-btn{display:flex;flex-direction:column;align-items:center;justify-content:center;gap:var(--space-xs);min-height:72px;padding:var(--space-sm);font-family:inherit;font-size:var(--font-size-xs);font-weight:var(--font-weight-semibold);text-align:center;color:#fff;border:none;border-radius:var(--radius-lg);cursor:pointer;transition:all var(--transition-fast);-webkit-appearance:none;-moz-appearance:none;appearance:none;-webkit-user-select:none;user-select:none;touch-action:manipulation}.grade-btn:active{transform:scale(.95)}.grade-btn-1{background-color:var(--color-grade-1)}.grade-btn-1:active{background-color:var(--color-grade-1-dark)}.grade-btn-2{background-color:var(--color-grade-2)}.grade-btn-2:active{background-color:var(--color-grade-2-dark)}.grade-btn-3{background-color:var(--color-grade-3)}.grade-btn-3:active{background-color:var(--color-grade-3-dark)}.grade-btn-4{background-color:var(--color-grade-4)}.grade-btn-4:active{background-color:var(--color-grade-4-dark)}.grade-btn-label{font-size:var(--font-size-xs);line-height:1.2}.progress-bar{height:8px;background-color:var(--color-border);border-radius:var(--radius-full);overflow:hidden}.progress-bar-fill{height:100%;background-color:var(--color-primary);border-radius:var(--radius-full);transition:width var(--transition-normal)}.progress-text{font-size:var(--font-size-sm);color:var(--color-text-secondary)}.badge{display:inline-flex;align-items:center;gap:var(--space-xs);padding:var(--space-xs) var(--space-sm);font-size:var(--font-size-xs);font-weight:var(--font-weight-medium);border-radius:var(--radius-full);background-color:var(--color-background-secondary);color:var(--color-text-secondary)}.badge-streak{background-color:#f973161a;color:var(--color-streak)}.streak-display{display:flex;align-items:center;gap:var(--space-sm);padding:var(--space-md);background-color:#f973161a;border-radius:var(--radius-lg)}.streak-icon{font-size:var(--font-size-2xl)}.streak-count{font-size:var(--font-size-2xl);font-weight:var(--font-weight-bold);color:var(--color-streak)}.streak-label{font-size:var(--font-size-sm);color:var(--color-text-secondary)}.header{display:flex;align-items:center;justify-content:space-between;padding:var(--space-md);background-color:var(--color-surface);border-bottom:1px solid var(--color-border);position:sticky;top:0;z-index:100}.header-title{font-size:var(--font-size-lg);font-weight:var(--font-weight-semibold)}.header-back{display:flex;align-items:center;justify-content:center;width:var(--tap-target-min);height:var(--tap-target-min);margin-left:calc(-1 * var(--space-sm));color:var(--color-text-secondary);border-radius:var(--radius-md);transition:background-color var(--transition-fast)}.header-back:hover{background-color:var(--color-background-secondary);text-decoration:none}.header-action{display:flex;align-items:center;justify-content:center;min-width:var(--tap-target-min);min-height:var(--tap-target-min);color:var(--color-primary);font-weight:var(--font-weight-medium)}.flashcard{flex:1;display:flex;flex-direction:column}.flashcard-progress{padding:var(--space-md);text-align:center;background-color:var(--color-background-secondary);border-bottom:1px solid var(--color-border)}.flashcard-progress-main{font-size:var(--font-size-lg);font-weight:var(--font-weight-semibold);color:var(--color-text-primary)}.flashcard-progress-sub{font-size:var(--font-size-sm);color:var(--color-text-muted);margin-top:var(--space-xs)}.flashcard-content{flex:1;display:flex;flex-direction:column;justify-content:center;padding:var(--space-xl)}.flashcard-question{font-size:var(--font-size-xl);font-weight:var(--font-weight-medium);text-align:center;line-height:var(--line-height-relaxed);margin-bottom:var(--space-xl)}.flashcard-answer-area{min-height:120px;display:flex;flex-direction:column;align-items:center;justify-content:center}.flashcard-reveal-btn{padding:var(--space-md) var(--space-xl);font-size:var(--font-size-base);color:var(--color-text-muted);background-color:var(--color-background-secondary);border:2px dashed var(--color-border);border-radius:var(--radius-lg);cursor:pointer;transition:all var(--transition-fast)}.flashcard-reveal-btn:hover{border-color:var(--color-primary);color:var(--color-primary)}.flashcard-answer{font-size:var(--font-size-xl);font-weight:var(--font-weight-medium);text-align:center;line-height:var(--line-height-relaxed);color:var(--color-primary);animation:fadeIn var(--transition-normal)}@keyframes fadeIn{0%{opacity:0;transform:translateY(8px)}to{opacity:1;transform:translateY(0)}}.child-item{display:flex;align-items:center;gap:var(--space-md);padding:var(--space-lg);background-color:var(--color-surface);border:1px solid var(--color-border);border-radius:var(--radius-lg);text-decoration:none;color:inherit;transition:all var(--transition-fast)}.child-item:hover{border-color:var(--color-primary-light);box-shadow:var(--shadow-md)}.child-avatar{width:48px;height:48px;display:flex;align-items:center;justify-content:center;font-size:var(--font-size-xl);font-weight:var(--font-weight-semibold);color:var(--color-primary);background-color:#2563eb1a;border-radius:var(--radius-full)}.child-info{flex:1;min-width:0}.child-name{font-size:var(--font-size-lg);font-weight:var(--font-weight-semibold);color:var(--color-text-primary);margin-bottom:var(--space-xs)}.child-progress{font-size:var(--font-size-sm);color:var(--color-text-secondary)}.child-action{flex-shrink:0}.empty-state{text-align:center;padding:var(--space-2xl) var(--space-lg)}.empty-state-icon{font-size:3rem;margin-bottom:var(--space-md);opacity:.5}.empty-state-title{font-size:var(--font-size-lg);font-weight:var(--font-weight-semibold);color:var(--color-text-primary);margin-bottom:var(--space-sm)}.empty-state-text{font-size:var(--font-size-base);color:var(--color-text-secondary);margin-bottom:var(--space-lg)}.settings-section{margin-bottom:var(--space-xl)}.settings-section-title{font-size:var(--font-size-sm);font-weight:var(--font-weight-semibold);color:var(--color-text-muted);text-transform:uppercase;letter-spacing:.05em;margin-bottom:var(--space-md)}.settings-item{display:flex;align-items:center;justify-content:space-between;padding:var(--space-md);background-color:var(--color-surface);border:1px solid var(--color-border);border-radius:var(--radius-lg);margin-bottom:var(--space-sm)}.settings-item-label{font-weight:var(--font-weight-medium)}.settings-item-value{color:var(--color-text-secondary)}.session-complete{text-align:center;padding:var(--space-2xl) var(--space-lg)}.session-complete-icon{font-size:4rem;margin-bottom:var(--space-lg)}.session-complete-title{font-size:var(--font-size-2xl);font-weight:var(--font-weight-bold);color:var(--color-text-primary);margin-bottom:var(--space-sm)}.session-complete-subtitle{font-size:var(--font-size-lg);color:var(--color-text-secondary);margin-bottom:var(--space-xl)}.session-stats{display:grid;grid-template-columns:repeat(3,1fr);gap:var(--space-md);margin-bottom:var(--space-xl)}.session-stat{text-align:center}.session-stat-value{font-size:var(--font-size-2xl);font-weight:var(--font-weight-bold);color:var(--color-primary)}.session-stat-label{font-size:var(--font-size-xs);color:var(--color-text-muted);text-transform:uppercase}.auth-page{min-height:100vh;min-height:100dvh;display:flex;flex-direction:column;align-items:center;justify-content:center;padding:var(--space-lg)}.auth-logo{font-size:var(--font-size-3xl);font-weight:var(--font-weight-bold);color:var(--color-primary);margin-bottom:var(--space-sm)}.auth-tagline{font-size:var(--font-size-lg);color:var(--color-text-secondary);text-align:center;margin-bottom:var(--space-2xl)}.auth-card{width:100%;max-width:400px}.nav-bottom{display:flex;justify-content:space-around;padding:var(--space-sm) var(--space-md);padding-bottom:max(var(--space-sm),env(safe-area-inset-bottom));background-color:var(--color-surface);border-top:1px solid var(--color-border)}.nav-item{display:flex;flex-direction:column;align-items:center;gap:var(--space-xs);padding:var(--space-sm);min-width:64px;color:var(--color-text-muted);text-decoration:none;border-radius:var(--radius-md);transition:color var(--transition-fast)}.nav-item:hover,.nav-item.active{color:var(--color-primary)}.nav-item-icon{font-size:1.25rem}.nav-item-label{font-size:var(--font-size-xs);font-weight:var(--font-weight-medium)}@media(min-width:640px){.grade-buttons{max-width:480px;margin:0 auto;border-radius:var(--radius-lg) var(--radius-lg) 0 0}.grade-btn{min-height:80px}}@supports (padding: max(0px)){.header{padding-top:max(var(--space-md),env(safe-area-inset-top))}.container{padding-left:max(var(--space-md),env(safe-area-inset-left));padding-right:max(var(--space-md),env(safe-area-inset-right))}}