*{margin:0;padding:0;box-sizing:border-box}:root{--primary-color: #4CAF50;--primary-dark: #45a049;--secondary-color: #2196F3;--background: #f5f5f5;--surface: #ffffff;--text-primary: #333333;--text-secondary: #666666;--border: #e0e0e0;--error: #f44336;--success: #4CAF50;--warning: #ff9800;--shadow: 0 2px 8px rgba(0, 0, 0, .1)}body{font-family:-apple-system,BlinkMacSystemFont,Segoe UI,PingFang SC,Hiragino Sans GB,Microsoft YaHei,sans-serif;background-color:var(--background);color:var(--text-primary);line-height:1.6;-webkit-font-smoothing:antialiased;-moz-osx-font-smoothing:grayscale}#root{min-height:100vh;max-width:600px;margin:0 auto;background-color:var(--surface);box-shadow:var(--shadow)}.btn{padding:12px 24px;border:none;border-radius:8px;font-size:16px;font-weight:500;cursor:pointer;transition:all .3s;display:inline-block;text-align:center;text-decoration:none}.btn-primary{background-color:var(--primary-color);color:#fff}.btn-primary:hover{background-color:var(--primary-dark)}.btn-secondary{background-color:var(--secondary-color);color:#fff}.btn-outline{background-color:transparent;border:2px solid var(--primary-color);color:var(--primary-color)}.btn-outline:hover{background-color:var(--primary-color);color:#fff}.btn:disabled{opacity:.6;cursor:not-allowed}.input{width:100%;padding:12px;border:2px solid var(--border);border-radius:8px;font-size:16px;transition:border-color .3s}.input:focus{outline:none;border-color:var(--primary-color)}.textarea{width:100%;padding:12px;border:2px solid var(--border);border-radius:8px;font-size:16px;min-height:100px;resize:vertical;font-family:inherit;transition:border-color .3s}.textarea:focus{outline:none;border-color:var(--primary-color)}.card{background:var(--surface);border-radius:12px;padding:16px;margin-bottom:16px;box-shadow:var(--shadow)}.container{padding:16px;max-width:100%}.title{font-size:24px;font-weight:600;margin-bottom:16px;color:var(--text-primary)}.subtitle{font-size:18px;font-weight:500;margin-bottom:12px;color:var(--text-secondary)}.tag{display:inline-block;padding:4px 12px;border-radius:16px;font-size:12px;font-weight:500;margin-right:8px;margin-bottom:8px}.tag-word{background-color:#e3f2fd;color:#1976d2}.tag-grammar{background-color:#fff3e0;color:#f57c00}.tag-math{background-color:#f3e5f5;color:#7b1fa2}.rating-buttons{display:flex;gap:8px;margin-top:16px;flex-wrap:wrap}.rating-btn{flex:1;min-width:60px;padding:12px;border:2px solid var(--border);border-radius:8px;background:var(--surface);font-size:14px;cursor:pointer;transition:all .3s}.rating-btn:hover{border-color:var(--primary-color);background-color:#f0f8f0}.rating-btn.selected{background-color:var(--primary-color);color:#fff;border-color:var(--primary-color)}.empty-state{text-align:center;padding:48px 16px;color:var(--text-secondary)}.empty-state-icon{font-size:64px;margin-bottom:16px}.loading{text-align:center;padding:48px;color:var(--text-secondary)}.error{color:var(--error);font-size:14px;margin-top:8px}.success{color:var(--success);font-size:14px;margin-top:8px}.navbar{background:var(--surface);padding:16px;box-shadow:var(--shadow);display:flex;justify-content:space-between;align-items:center;position:sticky;top:0;z-index:100}.navbar-title{font-size:20px;font-weight:600;color:var(--text-primary)}.navbar-actions{display:flex;gap:8px}.stats-grid{display:grid;grid-template-columns:repeat(3,1fr);gap:12px;margin-bottom:24px}.stat-card{background:var(--surface);border-radius:12px;padding:16px;text-align:center;box-shadow:var(--shadow)}.stat-value{font-size:24px;font-weight:600;color:var(--primary-color);margin-bottom:4px}.stat-label{font-size:12px;color:var(--text-secondary)}@media (max-width: 480px){.container{padding:12px}.title{font-size:20px}.stats-grid{grid-template-columns:1fr}}