:root{--color-primary: #dc2626;--color-primary-dark: #b91c1c;--color-secondary: #fbbf24;--color-background: #fef3f2;--color-surface: #ffffff;--color-text: #1f2937;--color-text-light: #6b7280;--color-border: #e5e7eb;--color-success: #22c55e;--color-warning: #f97316;--color-error: #ef4444;--radius-sm: 4px;--radius-md: 8px;--radius-lg: 12px;--radius-xl: 16px;--shadow-sm: 0 1px 2px rgba(0, 0, 0, .05);--shadow-md: 0 4px 6px rgba(0, 0, 0, .1);--shadow-lg: 0 10px 15px rgba(0, 0, 0, .1);font-family:system-ui,-apple-system,BlinkMacSystemFont,Segoe UI,Roboto,sans-serif;line-height:1.5;font-weight:400;color:var(--color-text);background-color:var(--color-background)}*{box-sizing:border-box;margin:0;padding:0}body{min-height:100vh}#root{min-height:100vh;display:flex;flex-direction:column}h1,h2,h3,h4,h5,h6{font-weight:600;line-height:1.3}h1{font-size:1.75rem}h2{font-size:1.25rem}h3{font-size:1.125rem}@media (min-width: 640px){h1{font-size:2rem}h2{font-size:1.5rem}h3{font-size:1.25rem}}.hanzi{font-size:2rem;font-weight:400;line-height:1.2}.hanzi-large{font-size:3rem}@media (min-width: 640px){.hanzi{font-size:3rem}.hanzi-large{font-size:5rem}}.pinyin{font-size:1.25rem;color:var(--color-text-light)}a{color:var(--color-primary);text-decoration:none}a:hover{text-decoration:underline}.btn{display:inline-flex;align-items:center;justify-content:center;gap:.5rem;padding:.875rem 1.25rem;font-size:1rem;font-weight:500;border:none;border-radius:var(--radius-md);cursor:pointer;transition:all .2s;min-height:44px}.btn:disabled{opacity:.5;cursor:not-allowed}.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-surface);color:var(--color-text);border:1px solid var(--color-border)}.btn-secondary:hover:not(:disabled){background-color:var(--color-background)}.btn-success{background-color:var(--color-success);color:#fff}.btn-warning{background-color:var(--color-warning);color:#fff}.btn-error{background-color:var(--color-error);color:#fff}.btn-sm{padding:.5rem 1rem;font-size:.875rem}.btn-lg{padding:1rem 2rem;font-size:1.125rem}.btn-block{width:100%}.card{background-color:var(--color-surface);border-radius:var(--radius-lg);box-shadow:var(--shadow-md);padding:1rem}@media (min-width: 640px){.card{padding:1.5rem}}.form-group{margin-bottom:1rem}.form-label{display:block;margin-bottom:.5rem;font-weight:500}.form-input,.form-textarea{width:100%;padding:.75rem;font-size:1rem;border:1px solid var(--color-border);border-radius:var(--radius-md);background-color:var(--color-surface)}.form-input:focus,.form-textarea:focus{outline:none;border-color:var(--color-primary);box-shadow:0 0 0 3px #dc26261a}.form-textarea{min-height:100px;resize:vertical}.container{max-width:1200px;margin:0 auto;padding:0 1rem}@media (min-width: 640px){.container{padding:0 1.5rem}}.page{flex:1;padding:1rem 0}@media (min-width: 640px){.page{padding:2rem 0}}.header{background-color:var(--color-primary);color:#fff;padding:.75rem 0;position:sticky;top:0;z-index:100}.header a{color:#fff}.header-content{display:flex;justify-content:space-between;align-items:center}.header-title{font-size:1.125rem;font-weight:600}@media (min-width: 640px){.header-title{font-size:1.5rem}}.header-nav{display:flex;gap:.25rem}@media (min-width: 640px){.header-nav{gap:.5rem}}.header-nav a{padding:.5rem;font-size:.75rem;white-space:nowrap;border-radius:var(--radius-sm)}@media (min-width: 640px){.header-nav a{padding:.5rem .75rem;font-size:.875rem}}.header-nav a:hover{opacity:.8;text-decoration:none;background-color:#ffffff1a}.grid{display:grid;gap:.75rem}@media (min-width: 640px){.grid{gap:1rem}}.grid-cols-2{grid-template-columns:1fr}.grid-cols-3{grid-template-columns:repeat(3,1fr)}@media (min-width: 640px){.grid-cols-2{grid-template-columns:repeat(2,1fr)}}.text-center{text-align:center}.text-right{text-align:right}.text-light{color:var(--color-text-light)}.text-success{color:var(--color-success)}.text-error{color:var(--color-error)}.mt-1{margin-top:.5rem}.mt-2{margin-top:1rem}.mt-3{margin-top:1.5rem}.mt-4{margin-top:2rem}.mb-1{margin-bottom:.5rem}.mb-2{margin-bottom:1rem}.mb-3{margin-bottom:1.5rem}.mb-4{margin-bottom:2rem}.flex{display:flex}.flex-col{flex-direction:column}.items-center{align-items:center}.justify-center{justify-content:center}.justify-between{justify-content:space-between}.gap-1{gap:.5rem}.gap-2{gap:1rem}.gap-3{gap:1.5rem}.study-card{perspective:1000px}.study-card-inner{transition:transform .6s;transform-style:preserve-3d}.study-card.flipped .study-card-inner{transform:rotateY(180deg)}.rating-buttons{display:grid;grid-template-columns:repeat(2,1fr);gap:.5rem}@media (min-width: 480px){.rating-buttons{grid-template-columns:repeat(4,1fr)}}.rating-btn{padding:.875rem .5rem;font-weight:600;font-size:.875rem;border:none;border-radius:var(--radius-md);cursor:pointer;transition:transform .1s,box-shadow .1s;min-height:44px}@media (min-width: 640px){.rating-btn{padding:1rem;font-size:1rem}}.rating-btn:hover{transform:translateY(-2px);box-shadow:var(--shadow-md)}.rating-btn.again{background-color:#fecaca;color:#b91c1c}.rating-btn.hard{background-color:#fed7aa;color:#c2410c}.rating-btn.good{background-color:#bbf7d0;color:#166534}.rating-btn.easy{background-color:#bfdbfe;color:#1e40af}.spinner{width:40px;height:40px;border:4px solid var(--color-border);border-top-color:var(--color-primary);border-radius:50%;animation:spin 1s linear infinite}@keyframes spin{to{transform:rotate(360deg)}}.empty-state{text-align:center;padding:3rem;color:var(--color-text-light)}.empty-state-icon{font-size:4rem;margin-bottom:1rem}.deck-card{display:block;padding:1rem;background-color:var(--color-surface);border-radius:var(--radius-lg);box-shadow:var(--shadow-sm);border:1px solid var(--color-border);transition:box-shadow .2s,transform .2s}@media (min-width: 640px){.deck-card{padding:1.5rem}}.deck-card:hover{box-shadow:var(--shadow-md);transform:translateY(-2px);text-decoration:none}.deck-card:active{transform:scale(.98)}.deck-card-title{font-size:1.125rem;font-weight:600;margin-bottom:.5rem}@media (min-width: 640px){.deck-card-title{font-size:1.25rem}}.deck-card-stats{display:flex;gap:1rem;color:var(--color-text-light);font-size:.8125rem}@media (min-width: 640px){.deck-card-stats{font-size:.875rem}}.note-card{display:flex;flex-direction:column;gap:.75rem;padding:.875rem;background-color:var(--color-surface);border:1px solid var(--color-border);border-radius:var(--radius-md)}@media (min-width: 640px){.note-card{flex-direction:row;justify-content:space-between;align-items:flex-start;padding:1rem;gap:1rem}}.note-card-content{flex:1;min-width:0}.note-card-hanzi{font-size:1.25rem;margin-bottom:.25rem}@media (min-width: 640px){.note-card-hanzi{font-size:1.5rem}}.note-card-details{color:var(--color-text-light);font-size:.8125rem;word-wrap:break-word}@media (min-width: 640px){.note-card-details{font-size:.875rem}}.note-card-actions{display:flex;gap:.5rem;flex-shrink:0}.stats-card{text-align:center;padding:1rem}@media (min-width: 640px){.stats-card{padding:1.5rem}}.stats-value{font-size:1.75rem;font-weight:700;color:var(--color-primary)}@media (min-width: 640px){.stats-value{font-size:2.5rem}}.stats-label{color:var(--color-text-light);margin-top:.25rem;font-size:.75rem}@media (min-width: 640px){.stats-label{font-size:.875rem}}.modal-overlay{position:fixed;top:0;right:0;bottom:0;left:0;background-color:#00000080;display:flex;align-items:center;justify-content:center;padding:1rem;z-index:1000}.modal{background-color:var(--color-surface);border-radius:var(--radius-xl);padding:2rem;max-width:500px;width:100%;max-height:90vh;overflow-y:auto}.modal-header{display:flex;justify-content:space-between;align-items:center;margin-bottom:1.5rem}.modal-title{font-size:1.25rem;font-weight:600}.modal-close{background:none;border:none;font-size:1.5rem;cursor:pointer;color:var(--color-text-light)}.modal-actions{display:flex;flex-direction:column;gap:.5rem;margin-top:1.5rem}@media (min-width: 480px){.modal-actions{flex-direction:row;justify-content:flex-end}}@media (max-width: 639px){.hide-mobile{display:none!important}.btn-block-mobile{width:100%}}button,a,input,select,textarea{touch-action:manipulation}@media (max-width: 639px){input,select,textarea{font-size:16px!important}}@supports (padding: max(0px)){.page{padding-left:max(1rem,env(safe-area-inset-left));padding-right:max(1rem,env(safe-area-inset-right))}.header{padding-left:max(0px,env(safe-area-inset-left));padding-right:max(0px,env(safe-area-inset-right))}}